From ee18d823cf3048b56ad806f1b5f1a15b5c22637f Mon Sep 17 00:00:00 2001 From: nlohmann Date: Thu, 9 Jul 2026 17:20:06 +0000 Subject: [PATCH] deploy: d0de6a9111aa9aed9c4f881846ec2a05ee9b2501 --- api/adl_serializer/from_json/index.html | 2 +- api/adl_serializer/index.html | 2 +- api/adl_serializer/to_json/index.html | 2 +- api/basic_json/accept/index.html | 2 +- api/basic_json/array/index.html | 2 +- api/basic_json/array_t/index.html | 2 +- api/basic_json/at/index.html | 2 +- api/basic_json/back/index.html | 2 +- api/basic_json/basic_json/index.html | 2 +- api/basic_json/begin/index.html | 2 +- api/basic_json/binary/index.html | 2 +- api/basic_json/binary_t/index.html | 2 +- api/basic_json/boolean_t/index.html | 2 +- api/basic_json/cbegin/index.html | 2 +- api/basic_json/cbor_tag_handler_t/index.html | 2 +- api/basic_json/cend/index.html | 2 +- api/basic_json/clear/index.html | 2 +- api/basic_json/contains/index.html | 2 +- api/basic_json/count/index.html | 2 +- api/basic_json/crbegin/index.html | 2 +- api/basic_json/crend/index.html | 2 +- .../default_object_comparator_t/index.html | 2 +- api/basic_json/diff/index.html | 2 +- api/basic_json/dump/index.html | 2 +- api/basic_json/emplace/index.html | 2 +- api/basic_json/emplace_back/index.html | 2 +- api/basic_json/empty/index.html | 2 +- api/basic_json/end/index.html | 2 +- api/basic_json/end_pos/index.html | 2 +- api/basic_json/erase/index.html | 2 +- api/basic_json/error_handler_t/index.html | 2 +- api/basic_json/exception/index.html | 2 +- api/basic_json/find/index.html | 2 +- api/basic_json/flatten/index.html | 2 +- api/basic_json/format_as/index.html | 2 +- api/basic_json/from_bjdata/index.html | 2 +- api/basic_json/from_bson/index.html | 2 +- api/basic_json/from_cbor/index.html | 2 +- api/basic_json/from_msgpack/index.html | 2 +- api/basic_json/from_ubjson/index.html | 2 +- api/basic_json/front/index.html | 2 +- api/basic_json/get/index.html | 2 +- api/basic_json/get_allocator/index.html | 2 +- api/basic_json/get_binary/index.html | 2 +- api/basic_json/get_ptr/index.html | 2 +- api/basic_json/get_ref/index.html | 2 +- api/basic_json/get_to/index.html | 2 +- api/basic_json/index.html | 2 +- api/basic_json/input_format_t/index.html | 2 +- api/basic_json/insert/index.html | 2 +- api/basic_json/invalid_iterator/index.html | 2 +- api/basic_json/is_array/index.html | 2 +- api/basic_json/is_binary/index.html | 2 +- api/basic_json/is_boolean/index.html | 2 +- api/basic_json/is_discarded/index.html | 2 +- api/basic_json/is_null/index.html | 2 +- api/basic_json/is_number/index.html | 2 +- api/basic_json/is_number_float/index.html | 2 +- api/basic_json/is_number_integer/index.html | 2 +- api/basic_json/is_number_unsigned/index.html | 2 +- api/basic_json/is_object/index.html | 2 +- api/basic_json/is_primitive/index.html | 2 +- api/basic_json/is_string/index.html | 2 +- api/basic_json/is_structured/index.html | 2 +- api/basic_json/items/index.html | 2 +- api/basic_json/json_base_class_t/index.html | 2 +- api/basic_json/json_serializer/index.html | 2 +- api/basic_json/max_size/index.html | 2 +- api/basic_json/merge_patch/index.html | 2 +- api/basic_json/meta/index.html | 2 +- api/basic_json/number_float_t/index.html | 2 +- api/basic_json/number_integer_t/index.html | 2 +- api/basic_json/number_unsigned_t/index.html | 2 +- api/basic_json/object/index.html | 2 +- api/basic_json/object_comparator_t/index.html | 2 +- api/basic_json/object_t/index.html | 2 +- api/basic_json/operator+=/index.html | 2 +- api/basic_json/operator=/index.html | 2 +- api/basic_json/operator[]/index.html | 2 +- api/basic_json/operator_ValueType/index.html | 2 +- api/basic_json/operator_eq/index.html | 2 +- api/basic_json/operator_ge/index.html | 2 +- api/basic_json/operator_gt/index.html | 2 +- api/basic_json/operator_le/index.html | 2 +- api/basic_json/operator_lt/index.html | 2 +- api/basic_json/operator_ne/index.html | 2 +- api/basic_json/operator_spaceship/index.html | 2 +- api/basic_json/operator_value_t/index.html | 2 +- api/basic_json/other_error/index.html | 2 +- api/basic_json/out_of_range/index.html | 2 +- api/basic_json/parse/index.html | 2 +- api/basic_json/parse_error/index.html | 2 +- api/basic_json/parse_event_t/index.html | 2 +- api/basic_json/parser_callback_t/index.html | 2 +- api/basic_json/patch/index.html | 2 +- api/basic_json/patch_inplace/index.html | 2 +- api/basic_json/push_back/index.html | 2 +- api/basic_json/rbegin/index.html | 2 +- api/basic_json/rend/index.html | 2 +- api/basic_json/sax_parse/index.html | 2 +- api/basic_json/size/index.html | 2 +- api/basic_json/start_pos/index.html | 2 +- api/basic_json/std_formatter/index.html | 2 +- api/basic_json/std_hash/index.html | 2 +- api/basic_json/std_swap/index.html | 2 +- api/basic_json/string_t/index.html | 2 +- api/basic_json/swap/index.html | 2 +- api/basic_json/to_bjdata/index.html | 2 +- api/basic_json/to_bson/index.html | 2 +- api/basic_json/to_cbor/index.html | 2 +- api/basic_json/to_msgpack/index.html | 2 +- api/basic_json/to_string/index.html | 2 +- api/basic_json/to_ubjson/index.html | 2 +- api/basic_json/type/index.html | 2 +- api/basic_json/type_error/index.html | 2 +- api/basic_json/type_name/index.html | 2 +- api/basic_json/unflatten/index.html | 2 +- api/basic_json/update/index.html | 2 +- api/basic_json/value/index.html | 2 +- api/basic_json/value_t/index.html | 2 +- api/basic_json/~basic_json/index.html | 2 +- .../byte_container_with_subtype/index.html | 2 +- .../clear_subtype/index.html | 2 +- .../has_subtype/index.html | 2 +- api/byte_container_with_subtype/index.html | 2 +- .../set_subtype/index.html | 2 +- .../subtype/index.html | 2 +- api/json/index.html | 2 +- api/json_pointer/back/index.html | 2 +- api/json_pointer/empty/index.html | 2 +- api/json_pointer/front/index.html | 2 +- api/json_pointer/index.html | 2 +- api/json_pointer/json_pointer/index.html | 2 +- api/json_pointer/operator_eq/index.html | 2 +- api/json_pointer/operator_ne/index.html | 2 +- api/json_pointer/operator_slash/index.html | 2 +- api/json_pointer/operator_slasheq/index.html | 2 +- api/json_pointer/operator_string_t/index.html | 2 +- api/json_pointer/parent_pointer/index.html | 2 +- api/json_pointer/pop_back/index.html | 2 +- api/json_pointer/pop_front/index.html | 2 +- api/json_pointer/push_back/index.html | 2 +- api/json_pointer/push_front/index.html | 2 +- api/json_pointer/string_t/index.html | 2 +- api/json_pointer/to_string/index.html | 2 +- api/json_sax/binary/index.html | 2 +- api/json_sax/boolean/index.html | 2 +- api/json_sax/end_array/index.html | 2 +- api/json_sax/end_object/index.html | 2 +- api/json_sax/index.html | 2 +- api/json_sax/key/index.html | 2 +- api/json_sax/null/index.html | 2 +- api/json_sax/number_float/index.html | 2 +- api/json_sax/number_integer/index.html | 2 +- api/json_sax/number_unsigned/index.html | 2 +- api/json_sax/parse_error/index.html | 2 +- api/json_sax/start_array/index.html | 2 +- api/json_sax/start_object/index.html | 2 +- api/json_sax/string/index.html | 2 +- api/macros/index.html | 2 +- api/macros/json_assert/index.html | 2 +- .../json_brace_init_copy_semantics/index.html | 2 +- .../json_diagnostic_positions/index.html | 2 +- api/macros/json_diagnostics/index.html | 2 +- .../json_disable_enum_serialization/index.html | 2 +- api/macros/json_has_cpp_11/index.html | 2 +- api/macros/json_has_filesystem/index.html | 2 +- api/macros/json_has_ranges/index.html | 2 +- api/macros/json_has_static_rtti/index.html | 2 +- api/macros/json_has_std_format/index.html | 2 +- .../json_has_three_way_comparison/index.html | 2 +- api/macros/json_no_io/index.html | 2 +- api/macros/json_noexception/index.html | 2 +- .../json_skip_library_version_check/index.html | 2 +- .../index.html | 2 +- api/macros/json_throw_user/index.html | 2 +- api/macros/json_use_global_udls/index.html | 2 +- .../json_use_implicit_conversions/index.html | 2 +- .../index.html | 2 +- .../nlohmann_define_derived_type/index.html | 2 +- .../nlohmann_define_type_intrusive/index.html | 2 +- .../index.html | 2 +- .../nlohmann_define_type_with_names/index.html | 2 +- api/macros/nlohmann_json_namespace/index.html | 2 +- .../nlohmann_json_namespace_begin/index.html | 2 +- .../index.html | 2 +- .../nlohmann_json_serialize_enum/index.html | 2 +- .../index.html | 2 +- .../nlohmann_json_version_major/index.html | 2 +- api/operator_gtgt/index.html | 2 +- api/operator_literal_json/index.html | 2 +- api/operator_literal_json_pointer/index.html | 2 +- api/operator_ltlt/index.html | 2 +- api/ordered_json/index.html | 2 +- api/ordered_map/index.html | 2 +- community/code_of_conduct/index.html | 2 +- community/contribution_guidelines/index.html | 2 +- community/governance/index.html | 2 +- community/index.html | 2 +- community/quality_assurance/index.html | 2 +- community/security_policy/index.html | 2 +- features/arbitrary_types/index.html | 2 +- features/assertions/index.html | 2 +- features/binary_formats/bjdata/index.html | 2 +- features/binary_formats/bson/index.html | 2 +- features/binary_formats/cbor/index.html | 2 +- features/binary_formats/index.html | 2 +- features/binary_formats/messagepack/index.html | 2 +- features/binary_formats/ubjson/index.html | 2 +- features/binary_values/index.html | 2 +- features/comments/index.html | 2 +- features/conversions.md | 18 ++++++++++++++++++ features/conversions/index.html | 8 ++++++-- features/conversions/index.md | 16 ++++++++++++++++ features/creating_values/index.html | 2 +- .../element_access/checked_access/index.html | 2 +- .../element_access/default_value/index.html | 2 +- features/element_access/index.html | 2 +- .../element_access/unchecked_access/index.html | 2 +- features/enum_conversion/index.html | 2 +- features/index.html | 2 +- features/iterators/index.html | 2 +- features/json_patch/index.html | 2 +- features/json_pointer/index.html | 2 +- features/macros/index.html | 2 +- features/merge_patch/index.html | 2 +- features/modifying_values/index.html | 2 +- features/modules/index.html | 2 +- features/namespace/index.html | 2 +- features/object_order/index.html | 2 +- features/parsing/index.html | 2 +- features/parsing/json_lines/index.html | 2 +- features/parsing/parse_exceptions/index.html | 2 +- features/parsing/parser_callbacks/index.html | 2 +- features/parsing/sax_interface/index.html | 2 +- features/serialization/index.html | 2 +- features/trailing_commas/index.html | 2 +- features/types/index.html | 2 +- features/types/number_handling/index.html | 2 +- home/architecture/index.html | 2 +- home/customers/index.html | 2 +- home/design_goals/index.html | 2 +- home/exceptions/index.html | 2 +- home/faq/index.html | 2 +- home/license/index.html | 2 +- home/releases/index.html | 2 +- home/sponsors/index.html | 2 +- index.html | 2 +- integration/cmake/index.html | 2 +- integration/index.html | 2 +- integration/migration_guide/index.html | 2 +- integration/package_managers/index.html | 2 +- integration/pkg-config/index.html | 2 +- search/search_index.json | 2 +- 254 files changed, 291 insertions(+), 253 deletions(-) diff --git a/api/adl_serializer/from_json/index.html b/api/adl_serializer/from_json/index.html index 0472fbbb4..95b6277df 100644 --- a/api/adl_serializer/from_json/index.html +++ b/api/adl_serializer/from_json/index.html @@ -101,4 +101,4 @@ std::cout << p.name << " (" << p.age << ") lives in " << p.address << std::endl; }

Output:

Ned Flanders (60) lives in 744 Evergreen Terrace
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/adl_serializer/index.html b/api/adl_serializer/index.html index 3e112128a..2803d995c 100644 --- a/api/adl_serializer/index.html +++ b/api/adl_serializer/index.html @@ -12,4 +12,4 @@ // same thing, but with the "from_json" method } }; -

Member functions

Version history

\ No newline at end of file +

Member functions

Version history

\ No newline at end of file diff --git a/api/adl_serializer/to_json/index.html b/api/adl_serializer/to_json/index.html index c55ed68b2..3492abc8b 100644 --- a/api/adl_serializer/to_json/index.html +++ b/api/adl_serializer/to_json/index.html @@ -35,4 +35,4 @@ std::cout << j << std::endl; }

Output:

{"address":"744 Evergreen Terrace","age":60,"name":"Ned Flanders"}
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/accept/index.html b/api/basic_json/accept/index.html index 1db50c125..71696ff1c 100644 --- a/api/basic_json/accept/index.html +++ b/api/basic_json/accept/index.html @@ -36,4 +36,4 @@ << json::accept(invalid_text) << '\n'; }

Output:

true false
-

See also

Version history

Deprecation

Overload (2) replaces calls to accept with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like accept({ptr, ptr+len}, ...); with accept(ptr, ptr+len, ...);.

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

Overload (2) replaces calls to accept with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like accept({ptr, ptr+len}, ...); with accept(ptr, ptr+len, ...);.

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/array/index.html b/api/basic_json/array/index.html index 3d076030f..ccb70c5a1 100644 --- a/api/basic_json/array/index.html +++ b/api/basic_json/array/index.html @@ -22,4 +22,4 @@ [] [1,2,3,4] [["one",1],["two",2]] -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/array_t/index.html b/api/basic_json/array_t/index.html index ec6c1358e..22694c292 100644 --- a/api/basic_json/array_t/index.html +++ b/api/basic_json/array_t/index.html @@ -14,4 +14,4 @@ std::cout << std::boolalpha << std::is_same<std::vector<json>, json::array_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/at/index.html b/api/basic_json/at/index.html index e6780a148..24e4f21d7 100644 --- a/api/basic_json/at/index.html +++ b/api/basic_json/at/index.html @@ -498,4 +498,4 @@ [json.exception.out_of_range.402] array index '-' (2) is out of range [json.exception.out_of_range.403] key 'foo' not found [json.exception.out_of_range.404] unresolved reference token 'foo' -

See also

Version history

  1. Added in version 1.0.0.
  2. Added in version 1.0.0.
  3. Added in version 3.11.0.
  4. Added in version 2.0.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0.
  2. Added in version 1.0.0.
  3. Added in version 3.11.0.
  4. Added in version 2.0.0.
\ No newline at end of file diff --git a/api/basic_json/back/index.html b/api/basic_json/back/index.html index 2a6a7590a..065b3b30a 100644 --- a/api/basic_json/back/index.html +++ b/api/basic_json/back/index.html @@ -49,4 +49,4 @@ 16 "Hello, world" [json.exception.invalid_iterator.214] cannot get value -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/basic_json/index.html b/api/basic_json/basic_json/index.html index 6a16be7b6..69afae0c5 100644 --- a/api/basic_json/basic_json/index.html +++ b/api/basic_json/basic_json/index.html @@ -455,4 +455,4 @@ }

Output:

null
 23
-

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 2.1.0.
  4. Since version 3.2.0.
  5. Since version 1.0.0.
  6. Since version 1.0.0.
  7. Since version 1.0.0.
  8. Since version 1.0.0.
  9. Since version 1.0.0.
\ No newline at end of file +

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 2.1.0.
  4. Since version 3.2.0.
  5. Since version 1.0.0.
  6. Since version 1.0.0.
  7. Since version 1.0.0.
  8. Since version 1.0.0.
  9. Since version 1.0.0.
\ No newline at end of file diff --git a/api/basic_json/begin/index.html b/api/basic_json/begin/index.html index 4f9149b34..0a3b0861d 100644 --- a/api/basic_json/begin/index.html +++ b/api/basic_json/begin/index.html @@ -17,4 +17,4 @@ std::cout << *it << '\n'; }

Output:

1
-

Version history

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Version history

\ No newline at end of file diff --git a/api/basic_json/binary/index.html b/api/basic_json/binary/index.html index 9fd4063fc..d80877969 100644 --- a/api/basic_json/binary/index.html +++ b/api/basic_json/binary/index.html @@ -24,4 +24,4 @@ std::cout << "type: " << j.type_name() << ", subtype: " << j.get_binary().subtype() << std::endl; }

Output:

type: binary, subtype: 42
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/binary_t/index.html b/api/basic_json/binary_t/index.html index d6b96d3d1..493393147 100644 --- a/api/basic_json/binary_t/index.html +++ b/api/basic_json/binary_t/index.html @@ -10,4 +10,4 @@ std::cout << std::boolalpha << std::is_same<nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>, json::binary_t>::value << std::endl; }

Output:

true
-

See also

Version history

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See also

Version history

\ No newline at end of file diff --git a/api/basic_json/boolean_t/index.html b/api/basic_json/boolean_t/index.html index d9c2524e6..77275966d 100644 --- a/api/basic_json/boolean_t/index.html +++ b/api/basic_json/boolean_t/index.html @@ -10,4 +10,4 @@ std::cout << std::boolalpha << std::is_same<bool, json::boolean_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/cbegin/index.html b/api/basic_json/cbegin/index.html index 5673f0264..43dd265bd 100644 --- a/api/basic_json/cbegin/index.html +++ b/api/basic_json/cbegin/index.html @@ -16,4 +16,4 @@ std::cout << *it << '\n'; }

Output:

1
-

Version history

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Version history

\ No newline at end of file diff --git a/api/basic_json/cbor_tag_handler_t/index.html b/api/basic_json/cbor_tag_handler_t/index.html index d6dc67bad..06f0d2e71 100644 --- a/api/basic_json/cbor_tag_handler_t/index.html +++ b/api/basic_json/cbor_tag_handler_t/index.html @@ -35,4 +35,4 @@

Output:

[json.exception.parse_error.112] parse error at byte 1: syntax error while parsing CBOR value: invalid byte: 0xD8
 {"bytes":[202,254,186,190],"subtype":null}
 {"bytes":[202,254,186,190],"subtype":66}
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/cend/index.html b/api/basic_json/cend/index.html index 79f81601a..762c1d36d 100644 --- a/api/basic_json/cend/index.html +++ b/api/basic_json/cend/index.html @@ -19,4 +19,4 @@ std::cout << *it << '\n'; }

Output:

5
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/clear/index.html b/api/basic_json/clear/index.html index 8c3da7ed8..b756d3302 100644 --- a/api/basic_json/clear/index.html +++ b/api/basic_json/clear/index.html @@ -41,4 +41,4 @@ {} [] "" -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/contains/index.html b/api/basic_json/contains/index.html index b89953b51..112d4f0f7 100644 --- a/api/basic_json/contains/index.html +++ b/api/basic_json/contains/index.html @@ -101,4 +101,4 @@ false false false -

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 3.6.0. Extended template KeyType to support comparable types in version 3.11.0.
  3. Added in version 3.7.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 3.6.0. Extended template KeyType to support comparable types in version 3.11.0.
  3. Added in version 3.7.0.
\ No newline at end of file diff --git a/api/basic_json/count/index.html b/api/basic_json/count/index.html index cf7a23866..cbdd738cc 100644 --- a/api/basic_json/count/index.html +++ b/api/basic_json/count/index.html @@ -46,4 +46,4 @@ }

Output:

number of elements with key "two": 1
 number of elements with key "three": 0
-

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 1.0.0. Changed parameter key type to KeyType&& in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 1.0.0. Changed parameter key type to KeyType&& in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/crbegin/index.html b/api/basic_json/crbegin/index.html index cd0abb914..b9306a7ff 100644 --- a/api/basic_json/crbegin/index.html +++ b/api/basic_json/crbegin/index.html @@ -16,4 +16,4 @@ std::cout << *it << '\n'; }

Output:

5
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/crend/index.html b/api/basic_json/crend/index.html index 050235d0c..d4491a9c6 100644 --- a/api/basic_json/crend/index.html +++ b/api/basic_json/crend/index.html @@ -19,4 +19,4 @@ std::cout << *it << '\n'; }

Output:

1
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/default_object_comparator_t/index.html b/api/basic_json/default_object_comparator_t/index.html index effc5d9b1..49cb5bcbd 100644 --- a/api/basic_json/default_object_comparator_t/index.html +++ b/api/basic_json/default_object_comparator_t/index.html @@ -14,4 +14,4 @@ }

Output:

one < two : true
 three < four : false
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/diff/index.html b/api/basic_json/diff/index.html index de9907af7..58de24a5c 100644 --- a/api/basic_json/diff/index.html +++ b/api/basic_json/diff/index.html @@ -63,4 +63,4 @@ "world" ] } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/dump/index.html b/api/basic_json/dump/index.html index dc8686d5d..38fb8e9f1 100644 --- a/api/basic_json/dump/index.html +++ b/api/basic_json/dump/index.html @@ -105,4 +105,4 @@ [json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9 string with replaced invalid characters: "ä�ü" string with ignored invalid characters: "äü" -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/emplace/index.html b/api/basic_json/emplace/index.html index 11fd07033..fb6e4ed3e 100644 --- a/api/basic_json/emplace/index.html +++ b/api/basic_json/emplace/index.html @@ -37,4 +37,4 @@ 3 true {"A":"a","B":"b"} "b" false -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/emplace_back/index.html b/api/basic_json/emplace_back/index.html index fa241817f..4081161bb 100644 --- a/api/basic_json/emplace_back/index.html +++ b/api/basic_json/emplace_back/index.html @@ -28,4 +28,4 @@ null [1,2,3,4,5,6] ["first",["second","second","second"]] -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/empty/index.html b/api/basic_json/empty/index.html index 9d854c224..d8fe7d401 100644 --- a/api/basic_json/empty/index.html +++ b/api/basic_json/empty/index.html @@ -42,4 +42,4 @@ false true false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/end/index.html b/api/basic_json/end/index.html index b58dbf158..9ef552213 100644 --- a/api/basic_json/end/index.html +++ b/api/basic_json/end/index.html @@ -20,4 +20,4 @@ std::cout << *it << '\n'; }

Output:

5
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/end_pos/index.html b/api/basic_json/end_pos/index.html index 5b88e0a66..054696786 100644 --- a/api/basic_json/end_pos/index.html +++ b/api/basic_json/end_pos/index.html @@ -101,4 +101,4 @@ Original string: 1 Parsed string: 1 -

The output shows the start/end positions of all the objects and fields in the JSON string.

See also

Version history

\ No newline at end of file +

The output shows the start/end positions of all the objects and fields in the JSON string.

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/erase/index.html b/api/basic_json/erase/index.html index ba934ff59..a2048026a 100644 --- a/api/basic_json/erase/index.html +++ b/api/basic_json/erase/index.html @@ -148,4 +148,4 @@ std::cout << j_array << '\n'; }

Output:

[0,1,3,4,5]
-

See also

Version history

  1. Added in version 1.0.0. Added support for binary types in version 3.8.0.
  2. Added in version 1.0.0. Added support for binary types in version 3.8.0.
  3. Added in version 1.0.0.
  4. Added in version 3.11.0.
  5. Added in version 1.0.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Added support for binary types in version 3.8.0.
  2. Added in version 1.0.0. Added support for binary types in version 3.8.0.
  3. Added in version 1.0.0.
  4. Added in version 3.11.0.
  5. Added in version 1.0.0.
\ No newline at end of file diff --git a/api/basic_json/error_handler_t/index.html b/api/basic_json/error_handler_t/index.html index fde6cd4c0..e26728c15 100644 --- a/api/basic_json/error_handler_t/index.html +++ b/api/basic_json/error_handler_t/index.html @@ -30,4 +30,4 @@

Output:

[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9
 string with replaced invalid characters: "ä�ü"
 string with ignored invalid characters: "äü"
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/exception/index.html b/api/basic_json/exception/index.html index 26d22b384..c25f1a121 100644 --- a/api/basic_json/exception/index.html +++ b/api/basic_json/exception/index.html @@ -49,4 +49,4 @@ }

Output:

message: [json.exception.out_of_range.403] key 'non-existing' not found
 exception id: 403
-

See also

List of exceptions

Version history

\ No newline at end of file +

See also

List of exceptions

Version history

\ No newline at end of file diff --git a/api/basic_json/find/index.html b/api/basic_json/find/index.html index 30885abe2..04707105c 100644 --- a/api/basic_json/find/index.html +++ b/api/basic_json/find/index.html @@ -55,4 +55,4 @@

Output:

"two" was found: true
 value at key "two": 2
 "three" was found: false
-

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/flatten/index.html b/api/basic_json/flatten/index.html index 0e19942ad..18b225bd1 100644 --- a/api/basic_json/flatten/index.html +++ b/api/basic_json/flatten/index.html @@ -43,4 +43,4 @@ "/object/value": 42.99, "/pi": 3.141 } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/format_as/index.html b/api/basic_json/format_as/index.html index 3d822c876..f8680b552 100644 --- a/api/basic_json/format_as/index.html +++ b/api/basic_json/format_as/index.html @@ -84,4 +84,4 @@ std::cout << j_str << std::endl; }

Output:

{"one":1,"two":2}
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/from_bjdata/index.html b/api/basic_json/from_bjdata/index.html index 7aa591048..ec50fc56e 100644 --- a/api/basic_json/from_bjdata/index.html +++ b/api/basic_json/from_bjdata/index.html @@ -32,4 +32,4 @@ "compact": true, "schema": 0 } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/from_bson/index.html b/api/basic_json/from_bson/index.html index cccbc934c..ce63be928 100644 --- a/api/basic_json/from_bson/index.html +++ b/api/basic_json/from_bson/index.html @@ -33,4 +33,4 @@ "compact": true, "schema": 0 } -

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/from_cbor/index.html b/api/basic_json/from_cbor/index.html index 4e6671c72..a69ef9927 100644 --- a/api/basic_json/from_cbor/index.html +++ b/api/basic_json/from_cbor/index.html @@ -35,4 +35,4 @@ "compact": true, "schema": 0 } -

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/from_msgpack/index.html b/api/basic_json/from_msgpack/index.html index b70c7a58f..1befb0afa 100644 --- a/api/basic_json/from_msgpack/index.html +++ b/api/basic_json/from_msgpack/index.html @@ -32,4 +32,4 @@ "compact": true, "schema": 0 } -

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/from_ubjson/index.html b/api/basic_json/from_ubjson/index.html index 00765116b..9168b400f 100644 --- a/api/basic_json/from_ubjson/index.html +++ b/api/basic_json/from_ubjson/index.html @@ -32,4 +32,4 @@ "compact": true, "schema": 0 } -

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/front/index.html b/api/basic_json/front/index.html index d6c291fd8..233029abc 100644 --- a/api/basic_json/front/index.html +++ b/api/basic_json/front/index.html @@ -35,4 +35,4 @@ 1 1 "Hello, world" -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/get/index.html b/api/basic_json/get/index.html index c475b55ed..b45ec0814 100644 --- a/api/basic_json/get/index.html +++ b/api/basic_json/get/index.html @@ -103,4 +103,4 @@ }

Output:

17 17 17 17
 true
-

See also

Version history

  1. Since version 2.1.0.
  2. Since version 2.1.0. Extended to work with other specializations of basic_json in version 3.2.0.
  3. Since version 1.0.0.
\ No newline at end of file +

See also

Version history

  1. Since version 2.1.0.
  2. Since version 2.1.0. Extended to work with other specializations of basic_json in version 3.2.0.
  3. Since version 1.0.0.
\ No newline at end of file diff --git a/api/basic_json/get_allocator/index.html b/api/basic_json/get_allocator/index.html index 68e9cbca2..1ca9425fa 100644 --- a/api/basic_json/get_allocator/index.html +++ b/api/basic_json/get_allocator/index.html @@ -18,4 +18,4 @@ traits_t::deallocate(alloc, j, 1); }

Output:

"Hello, world!"
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/get_binary/index.html b/api/basic_json/get_binary/index.html index d4d8f0c4e..201baad2f 100644 --- a/api/basic_json/get_binary/index.html +++ b/api/basic_json/get_binary/index.html @@ -18,4 +18,4 @@ std::cout << "type: " << j.type_name() << ", subtype: " << j.get_binary().subtype() << std::endl; }

Output:

type: binary, subtype: 42
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/get_ptr/index.html b/api/basic_json/get_ptr/index.html index 3bdfa1f07..d8df45e2e 100644 --- a/api/basic_json/get_ptr/index.html +++ b/api/basic_json/get_ptr/index.html @@ -44,4 +44,4 @@ value at 0x6000029fc088 is 1 }

Output:

17 17 17 17
 true
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/get_ref/index.html b/api/basic_json/get_ref/index.html index 8dfce792d..71b9d0928 100644 --- a/api/basic_json/get_ref/index.html +++ b/api/basic_json/get_ref/index.html @@ -32,4 +32,4 @@ }

Output:

17 17
 [json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is number
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/get_to/index.html b/api/basic_json/get_to/index.html index cae8ecc60..2e07c59b6 100644 --- a/api/basic_json/get_to/index.html +++ b/api/basic_json/get_to/index.html @@ -74,4 +74,4 @@ null: null boolean: true array: [1,2,3,4,5] -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/index.html b/api/basic_json/index.html index 8a4435f7c..11177f802 100644 --- a/api/basic_json/index.html +++ b/api/basic_json/index.html @@ -78,4 +78,4 @@ "pi": 3.141, "size": 8 } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/input_format_t/index.html b/api/basic_json/input_format_t/index.html index 97f33a216..68f058605 100644 --- a/api/basic_json/input_format_t/index.html +++ b/api/basic_json/input_format_t/index.html @@ -123,4 +123,4 @@

Output:

binary(val=[...])
 
 result: true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/insert/index.html b/api/basic_json/insert/index.html index 7bdf4db3b..f9a4a4d0f 100644 --- a/api/basic_json/insert/index.html +++ b/api/basic_json/insert/index.html @@ -116,4 +116,4 @@

Output:

{"one":"eins","two":"zwei"}
 {"eleven":"elf","seventeen":"siebzehn"}
 {"eleven":"elf","one":"eins","seventeen":"siebzehn","two":"zwei"}
-

See also

Version history

  1. Added in version 1.0.0.
  2. Added in version 1.0.0.
  3. Added in version 1.0.0.
  4. Added in version 1.0.0.
  5. Added in version 3.0.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0.
  2. Added in version 1.0.0.
  3. Added in version 1.0.0.
  4. Added in version 1.0.0.
  5. Added in version 3.0.0.
\ No newline at end of file diff --git a/api/basic_json/invalid_iterator/index.html b/api/basic_json/invalid_iterator/index.html index 63d7f0fd0..6dce712e7 100644 --- a/api/basic_json/invalid_iterator/index.html +++ b/api/basic_json/invalid_iterator/index.html @@ -50,4 +50,4 @@ }

Output:

message: [json.exception.invalid_iterator.207] cannot use key() for non-object iterators
 exception id: 207
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/is_array/index.html b/api/basic_json/is_array/index.html index b43bf184d..2ff9520e5 100644 --- a/api/basic_json/is_array/index.html +++ b/api/basic_json/is_array/index.html @@ -38,4 +38,4 @@ true false false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_binary/index.html b/api/basic_json/is_binary/index.html index eadee79d4..eab33c4e5 100644 --- a/api/basic_json/is_binary/index.html +++ b/api/basic_json/is_binary/index.html @@ -38,4 +38,4 @@ false false true -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_boolean/index.html b/api/basic_json/is_boolean/index.html index f0b1f59a5..64e7974f2 100644 --- a/api/basic_json/is_boolean/index.html +++ b/api/basic_json/is_boolean/index.html @@ -38,4 +38,4 @@ false false false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_discarded/index.html b/api/basic_json/is_discarded/index.html index a746f1ee0..e381f775d 100644 --- a/api/basic_json/is_discarded/index.html +++ b/api/basic_json/is_discarded/index.html @@ -40,4 +40,4 @@ false false false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_null/index.html b/api/basic_json/is_null/index.html index 254b6d505..092c88417 100644 --- a/api/basic_json/is_null/index.html +++ b/api/basic_json/is_null/index.html @@ -38,4 +38,4 @@ false false false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_number/index.html b/api/basic_json/is_number/index.html index 919fec113..e03f5542f 100644 --- a/api/basic_json/is_number/index.html +++ b/api/basic_json/is_number/index.html @@ -42,4 +42,4 @@ false false false -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/is_number_float/index.html b/api/basic_json/is_number_float/index.html index d9d3cd79d..44ade0a57 100644 --- a/api/basic_json/is_number_float/index.html +++ b/api/basic_json/is_number_float/index.html @@ -38,4 +38,4 @@ false false false -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/is_number_integer/index.html b/api/basic_json/is_number_integer/index.html index 15a8abde6..07870a0a5 100644 --- a/api/basic_json/is_number_integer/index.html +++ b/api/basic_json/is_number_integer/index.html @@ -38,4 +38,4 @@ false false false -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/is_number_unsigned/index.html b/api/basic_json/is_number_unsigned/index.html index 16467d14b..8b534dcf2 100644 --- a/api/basic_json/is_number_unsigned/index.html +++ b/api/basic_json/is_number_unsigned/index.html @@ -38,4 +38,4 @@ false false false -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/is_object/index.html b/api/basic_json/is_object/index.html index 75b3ea283..d0ad212a9 100644 --- a/api/basic_json/is_object/index.html +++ b/api/basic_json/is_object/index.html @@ -38,4 +38,4 @@ false false false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_primitive/index.html b/api/basic_json/is_primitive/index.html index 3e6bdc2b7..54592feb6 100644 --- a/api/basic_json/is_primitive/index.html +++ b/api/basic_json/is_primitive/index.html @@ -42,4 +42,4 @@ false true true -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/is_string/index.html b/api/basic_json/is_string/index.html index 00fb8544d..822736b11 100644 --- a/api/basic_json/is_string/index.html +++ b/api/basic_json/is_string/index.html @@ -38,4 +38,4 @@ false true false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/is_structured/index.html b/api/basic_json/is_structured/index.html index f53812017..54274e5a5 100644 --- a/api/basic_json/is_structured/index.html +++ b/api/basic_json/is_structured/index.html @@ -42,4 +42,4 @@ true false false -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/items/index.html b/api/basic_json/items/index.html index bee99e77d..19017f958 100644 --- a/api/basic_json/items/index.html +++ b/api/basic_json/items/index.html @@ -47,4 +47,4 @@ key: 2, value: 4 key: 3, value: 8 key: 4, value: 16 -

See also

Version history

Deprecation

This function replaces the static function iterator_wrapper which was introduced in version 1.0.0, but has been deprecated in version 3.1.0. Function iterator_wrapper will be removed in version 4.0.0. Please replace all occurrences of iterator_wrapper(j) with j.items().

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

This function replaces the static function iterator_wrapper which was introduced in version 1.0.0, but has been deprecated in version 3.1.0. Function iterator_wrapper will be removed in version 4.0.0. Please replace all occurrences of iterator_wrapper(j) with j.items().

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/json_base_class_t/index.html b/api/basic_json/json_base_class_t/index.html index 5c0519173..5a2b4ebe1 100644 --- a/api/basic_json/json_base_class_t/index.html +++ b/api/basic_json/json_base_class_t/index.html @@ -91,4 +91,4 @@ /null - metadata = 42 -> null /object - metadata = 21 -> {"uint":1} /object/uint - metadata = 42 -> 1 -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/json_serializer/index.html b/api/basic_json/json_serializer/index.html index 27150c204..3a823196c 100644 --- a/api/basic_json/json_serializer/index.html +++ b/api/basic_json/json_serializer/index.html @@ -54,4 +54,4 @@ std::cout << p.name << " (" << p.age << ") lives in " << p.address << std::endl; }

Output:

Ned Flanders (60) lives in 744 Evergreen Terrace
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/max_size/index.html b/api/basic_json/max_size/index.html index 64a261d47..0246fcf05 100644 --- a/api/basic_json/max_size/index.html +++ b/api/basic_json/max_size/index.html @@ -31,4 +31,4 @@ 115292150460684697 576460752303423487 1 -

Note the output is platform-dependent.

Version history

\ No newline at end of file +

Note the output is platform-dependent.

Version history

\ No newline at end of file diff --git a/api/basic_json/merge_patch/index.html b/api/basic_json/merge_patch/index.html index 09f01ae67..df85dec47 100644 --- a/api/basic_json/merge_patch/index.html +++ b/api/basic_json/merge_patch/index.html @@ -64,4 +64,4 @@ ], "title": "Hello!" } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/meta/index.html b/api/basic_json/meta/index.html index 7dc8c8325..e630a93ce 100644 --- a/api/basic_json/meta/index.html +++ b/api/basic_json/meta/index.html @@ -27,4 +27,4 @@ "string": "3.12.0" } } -

Note the output is platform-dependent.

See also

Version history

\ No newline at end of file +

Note the output is platform-dependent.

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/number_float_t/index.html b/api/basic_json/number_float_t/index.html index b40a652ca..666a465cf 100644 --- a/api/basic_json/number_float_t/index.html +++ b/api/basic_json/number_float_t/index.html @@ -10,4 +10,4 @@ std::cout << std::boolalpha << std::is_same<double, json::number_float_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/number_integer_t/index.html b/api/basic_json/number_integer_t/index.html index c8aa924a1..1ea75d12f 100644 --- a/api/basic_json/number_integer_t/index.html +++ b/api/basic_json/number_integer_t/index.html @@ -10,4 +10,4 @@ std::cout << std::boolalpha << std::is_same<std::int64_t, json::number_integer_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/number_unsigned_t/index.html b/api/basic_json/number_unsigned_t/index.html index 2483ced31..4f2fd35f0 100644 --- a/api/basic_json/number_unsigned_t/index.html +++ b/api/basic_json/number_unsigned_t/index.html @@ -10,4 +10,4 @@ std::cout << std::boolalpha << std::is_same<std::uint64_t, json::number_unsigned_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/object/index.html b/api/basic_json/object/index.html index 1b28c7da5..b3a9c9d6a 100644 --- a/api/basic_json/object/index.html +++ b/api/basic_json/object/index.html @@ -31,4 +31,4 @@ {} {"one":1,"two":2} [json.exception.type_error.301] cannot create object from initializer list -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/object_comparator_t/index.html b/api/basic_json/object_comparator_t/index.html index 2c2afcec6..5bde5e989 100644 --- a/api/basic_json/object_comparator_t/index.html +++ b/api/basic_json/object_comparator_t/index.html @@ -14,4 +14,4 @@ }

Output:

json::object_comparator_t("one", "two") = true
 json::object_comparator_t("three", "four") = false
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/object_t/index.html b/api/basic_json/object_t/index.html index 18952d4fc..50c2e068a 100644 --- a/api/basic_json/object_t/index.html +++ b/api/basic_json/object_t/index.html @@ -28,4 +28,4 @@ std::cout << std::boolalpha << std::is_same<std::map<json::string_t, json>, json::object_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/operator+=/index.html b/api/basic_json/operator+=/index.html index 86e6bce5e..26d48e04e 100644 --- a/api/basic_json/operator+=/index.html +++ b/api/basic_json/operator+=/index.html @@ -96,4 +96,4 @@ null {"four":4,"one":1,"three":3,"two":2} [["five",5]] -

See also

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 2.0.0.
\ No newline at end of file +

See also

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 2.0.0.
\ No newline at end of file diff --git a/api/basic_json/operator=/index.html b/api/basic_json/operator=/index.html index b11636c2b..e0c1d4723 100644 --- a/api/basic_json/operator=/index.html +++ b/api/basic_json/operator=/index.html @@ -25,4 +25,4 @@ }

Output:

23
 23
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/operator[]/index.html b/api/basic_json/operator[]/index.html index b738b3e4c..108d12581 100644 --- a/api/basic_json/operator[]/index.html +++ b/api/basic_json/operator[]/index.html @@ -283,4 +283,4 @@ "foo" [1,2] 2 -

See also

Version history

  1. Added in version 1.0.0.
  2. Added in version 1.0.0. Added overloads for T* key in version 1.1.0. Removed overloads for T* key (replaced by 3) in version 3.11.0.
  3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept std::string_view-convertible keys, as already supported by at, value, find, and other lookup functions.
  4. Added in version 2.0.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0.
  2. Added in version 1.0.0. Added overloads for T* key in version 1.1.0. Removed overloads for T* key (replaced by 3) in version 3.11.0.
  3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept std::string_view-convertible keys, as already supported by at, value, find, and other lookup functions.
  4. Added in version 2.0.0.
\ No newline at end of file diff --git a/api/basic_json/operator_ValueType/index.html b/api/basic_json/operator_ValueType/index.html index fb667bf83..5a19e01d7 100644 --- a/api/basic_json/operator_ValueType/index.html +++ b/api/basic_json/operator_ValueType/index.html @@ -76,4 +76,4 @@ boolean: true array: [1,2,3,4,5] [json.exception.type_error.302] type must be boolean, but is string -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/operator_eq/index.html b/api/basic_json/operator_eq/index.html index 6ffe5f408..6911f2f26 100644 --- a/api/basic_json/operator_eq/index.html +++ b/api/basic_json/operator_eq/index.html @@ -115,4 +115,4 @@ 17 == nullptr false "foo" == nullptr false null == nullptr true -

See also

Version history

  1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
  2. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
  2. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_ge/index.html b/api/basic_json/operator_ge/index.html index f723e805a..dcc0048a6 100644 --- a/api/basic_json/operator_ge/index.html +++ b/api/basic_json/operator_ge/index.html @@ -34,4 +34,4 @@ {"A":"a","B":"b"} >= {"A":"a","B":"b"} true 17 >= 17.0000000000001 false "foo" >= "bar" true -

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_gt/index.html b/api/basic_json/operator_gt/index.html index c38b7919d..5240c4012 100644 --- a/api/basic_json/operator_gt/index.html +++ b/api/basic_json/operator_gt/index.html @@ -34,4 +34,4 @@ {"A":"a","B":"b"} > {"A":"a","B":"b"} false 17 > 17.0000000000001 false "foo" > "bar" true -

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_le/index.html b/api/basic_json/operator_le/index.html index b719ee7e7..4d7819f22 100644 --- a/api/basic_json/operator_le/index.html +++ b/api/basic_json/operator_le/index.html @@ -34,4 +34,4 @@ {"A":"a","B":"b"} <= {"A":"a","B":"b"} true 17 <= 17.0000000000001 true "foo" <= "bar" false -

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_lt/index.html b/api/basic_json/operator_lt/index.html index 2a86fcbd0..7be3933c8 100644 --- a/api/basic_json/operator_lt/index.html +++ b/api/basic_json/operator_lt/index.html @@ -34,4 +34,4 @@ {"A":"a","B":"b"} == {"A":"a","B":"b"} false 17 == 17.0000000000001 true "foo" == "bar" false -

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
  2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_ne/index.html b/api/basic_json/operator_ne/index.html index 176ca612f..ddbabdb81 100644 --- a/api/basic_json/operator_ne/index.html +++ b/api/basic_json/operator_ne/index.html @@ -69,4 +69,4 @@ 17 != nullptr true "foo" != nullptr true null != nullptr false -

Version history

  1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
  2. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
\ No newline at end of file +

Version history

  1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
  2. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_spaceship/index.html b/api/basic_json/operator_spaceship/index.html index 63488a31c..113c2fc91 100644 --- a/api/basic_json/operator_spaceship/index.html +++ b/api/basic_json/operator_spaceship/index.html @@ -93,4 +93,4 @@ 17 <=> 17.000000 := equivalent 17 <=> nan := unordered "17" <=> 17 := greater -

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 3.11.0.
  2. Added in version 3.11.0.
\ No newline at end of file diff --git a/api/basic_json/operator_value_t/index.html b/api/basic_json/operator_value_t/index.html index 8ad4be0e6..0e0b148ce 100644 --- a/api/basic_json/operator_value_t/index.html +++ b/api/basic_json/operator_value_t/index.html @@ -45,4 +45,4 @@ true true true -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/other_error/index.html b/api/basic_json/other_error/index.html index 990198604..4f34195e5 100644 --- a/api/basic_json/other_error/index.html +++ b/api/basic_json/other_error/index.html @@ -59,4 +59,4 @@ }

Output:

message: [json.exception.other_error.501] unsuccessful: {"op":"test","path":"/best_biscuit/name","value":"Choco Leibniz"}
 exception id: 501
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/out_of_range/index.html b/api/basic_json/out_of_range/index.html index 7fca76424..066b1b164 100644 --- a/api/basic_json/out_of_range/index.html +++ b/api/basic_json/out_of_range/index.html @@ -49,4 +49,4 @@ }

Output:

message: [json.exception.out_of_range.401] array index 4 is out of range
 exception id: 401
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/parse/index.html b/api/basic_json/parse/index.html index 980f58c46..4521b0eaf 100644 --- a/api/basic_json/parse/index.html +++ b/api/basic_json/parse/index.html @@ -424,4 +424,4 @@ "Neptune" ] } -

See also

Version history

Deprecation

Overload (2) replaces calls to parse with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like parse({ptr, ptr+len}, ...); with parse(ptr, ptr+len, ...);.

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file +

See also

Version history

Deprecation

Overload (2) replaces calls to parse with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like parse({ptr, ptr+len}, ...); with parse(ptr, ptr+len, ...);.

You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

\ No newline at end of file diff --git a/api/basic_json/parse_error/index.html b/api/basic_json/parse_error/index.html index 23a7f1931..7dca8c2f0 100644 --- a/api/basic_json/parse_error/index.html +++ b/api/basic_json/parse_error/index.html @@ -50,4 +50,4 @@

Output:

message: [json.exception.parse_error.101] parse error at line 1, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
 exception id: 101
 byte position of error: 8
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/parse_event_t/index.html b/api/basic_json/parse_event_t/index.html index cf9fa0462..3d31911c8 100644 --- a/api/basic_json/parse_event_t/index.html +++ b/api/basic_json/parse_event_t/index.html @@ -6,4 +6,4 @@ key, value }; -

The parser callback distinguishes the following events:

Examples

Example when certain parse events are triggered

See also

Version history

\ No newline at end of file +

The parser callback distinguishes the following events:

Examples

Example when certain parse events are triggered

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/parser_callback_t/index.html b/api/basic_json/parser_callback_t/index.html index 80d48947e..eff0ad188 100644 --- a/api/basic_json/parser_callback_t/index.html +++ b/api/basic_json/parser_callback_t/index.html @@ -83,4 +83,4 @@ "Width": 800 } } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/patch/index.html b/api/basic_json/patch/index.html index f9d74fc72..4a3b61d21 100644 --- a/api/basic_json/patch/index.html +++ b/api/basic_json/patch/index.html @@ -43,4 +43,4 @@ "world" ] } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/patch_inplace/index.html b/api/basic_json/patch_inplace/index.html index f8eb49f84..53279765a 100644 --- a/api/basic_json/patch_inplace/index.html +++ b/api/basic_json/patch_inplace/index.html @@ -47,4 +47,4 @@ "world" ] } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/push_back/index.html b/api/basic_json/push_back/index.html index 38ee6c160..cceb43692 100644 --- a/api/basic_json/push_back/index.html +++ b/api/basic_json/push_back/index.html @@ -96,4 +96,4 @@ null {"four":4,"one":1,"three":3,"two":2} [["five",5]] -

See also

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 2.0.0.
\ No newline at end of file +

See also

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 2.0.0.
\ No newline at end of file diff --git a/api/basic_json/rbegin/index.html b/api/basic_json/rbegin/index.html index 040adf908..0bbee89ea 100644 --- a/api/basic_json/rbegin/index.html +++ b/api/basic_json/rbegin/index.html @@ -17,4 +17,4 @@ std::cout << *it << '\n'; }

Output:

5
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/rend/index.html b/api/basic_json/rend/index.html index 559ac3ca7..04a229eeb 100644 --- a/api/basic_json/rend/index.html +++ b/api/basic_json/rend/index.html @@ -20,4 +20,4 @@ std::cout << *it << '\n'; }

Output:

1
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/sax_parse/index.html b/api/basic_json/sax_parse/index.html index 4a9ef8f64..101edb28e 100644 --- a/api/basic_json/sax_parse/index.html +++ b/api/basic_json/sax_parse/index.html @@ -183,4 +183,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

See also

Version history

Deprecation

Overload (2) replaces calls to sax_parse with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like sax_parse({ptr, ptr+len}); with sax_parse(ptr, ptr+len);.

\ No newline at end of file +

See also

Version history

Deprecation

Overload (2) replaces calls to sax_parse with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like sax_parse({ptr, ptr+len}); with sax_parse(ptr, ptr+len);.

\ No newline at end of file diff --git a/api/basic_json/size/index.html b/api/basic_json/size/index.html index f4cf37231..7704acc8d 100644 --- a/api/basic_json/size/index.html +++ b/api/basic_json/size/index.html @@ -37,4 +37,4 @@ 5 0 1 -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/start_pos/index.html b/api/basic_json/start_pos/index.html index 2d808867f..26d8b9c69 100644 --- a/api/basic_json/start_pos/index.html +++ b/api/basic_json/start_pos/index.html @@ -101,4 +101,4 @@ Original string: 1 Parsed string: 1 -

The output shows the start/end positions of all the objects and fields in the JSON string.

See also

Version history

\ No newline at end of file +

The output shows the start/end positions of all the objects and fields in the JSON string.

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/std_formatter/index.html b/api/basic_json/std_formatter/index.html index 08898cb6f..21121e339 100644 --- a/api/basic_json/std_formatter/index.html +++ b/api/basic_json/std_formatter/index.html @@ -40,4 +40,4 @@ ...."one": 1, ...."two": 2 } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/std_hash/index.html b/api/basic_json/std_hash/index.html index d5b6ed0da..d5ef3a80e 100644 --- a/api/basic_json/std_hash/index.html +++ b/api/basic_json/std_hash/index.html @@ -28,4 +28,4 @@ hash({}) = 2654435832 hash([]) = 2654435899 hash({"hello": "world"}) = 4469488738203676328 -

Note the output is platform-dependent.

Version history

\ No newline at end of file +

Note the output is platform-dependent.

Version history

\ No newline at end of file diff --git a/api/basic_json/std_swap/index.html b/api/basic_json/std_swap/index.html index b8a1473b9..bbbfaab28 100644 --- a/api/basic_json/std_swap/index.html +++ b/api/basic_json/std_swap/index.html @@ -26,4 +26,4 @@ }

Output:

j1 = {"one":1,"two":2} | j2 = [1,2,4,8,16]
 j1 = [1,2,4,8,16] | j2 = {"one":1,"two":2}
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/string_t/index.html b/api/basic_json/string_t/index.html index 356780a4f..0caa7a555 100644 --- a/api/basic_json/string_t/index.html +++ b/api/basic_json/string_t/index.html @@ -10,4 +10,4 @@ std::cout << std::boolalpha << std::is_same<std::string, json::string_t>::value << std::endl; }

Output:

true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/swap/index.html b/api/basic_json/swap/index.html index b7d1b8bc5..e3a0863e7 100644 --- a/api/basic_json/swap/index.html +++ b/api/basic_json/swap/index.html @@ -136,4 +136,4 @@ }

Output:

value = {"bytes":[4,5,6],"subtype":null}
 binary = {"bytes":[1,2,3],"subtype":null}
-

See also

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 1.0.0.
  4. Since version 1.0.0.
  5. Since version 1.0.0.
  6. Since version 3.8.0.
  7. Since version 3.8.0.
\ No newline at end of file +

See also

Version history

  1. Since version 1.0.0.
  2. Since version 1.0.0.
  3. Since version 1.0.0.
  4. Since version 1.0.0.
  5. Since version 1.0.0.
  6. Since version 3.8.0.
  7. Since version 3.8.0.
\ No newline at end of file diff --git a/api/basic_json/to_bjdata/index.html b/api/basic_json/to_bjdata/index.html index d9d4ab015..dfbd3f88e 100644 --- a/api/basic_json/to_bjdata/index.html +++ b/api/basic_json/to_bjdata/index.html @@ -79,4 +79,4 @@ [i1i2i3i4i5i6i7i8] [#i8i1i2i3i4i5i6i7i8 [$i#i812345678 -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/to_bson/index.html b/api/basic_json/to_bson/index.html index 8e15e7b91..5e6d23ff8 100644 --- a/api/basic_json/to_bson/index.html +++ b/api/basic_json/to_bson/index.html @@ -27,4 +27,4 @@ std::cout << std::endl; }

Output:

0x1b 0x00 0x00 0x00 0x08 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0x00 0x01 0x10 0x73 0x63 0x68 0x65 0x6d 0x61 0x00 0x00 0x00 0x00 0x00 0x00 
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/to_cbor/index.html b/api/basic_json/to_cbor/index.html index ff246badb..487f72ba1 100644 --- a/api/basic_json/to_cbor/index.html +++ b/api/basic_json/to_cbor/index.html @@ -27,4 +27,4 @@ std::cout << std::endl; }

Output:

0xa2 0x67 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0xf5 0x66 0x73 0x63 0x68 0x65 0x6d 0x61 0x00 
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/to_msgpack/index.html b/api/basic_json/to_msgpack/index.html index a4086f212..69c793908 100644 --- a/api/basic_json/to_msgpack/index.html +++ b/api/basic_json/to_msgpack/index.html @@ -27,4 +27,4 @@ std::cout << std::endl; }

Output:

0x82 0xa7 0x63 0x6f 0x6d 0x70 0x61 0x63 0x74 0xc3 0xa6 0x73 0x63 0x68 0x65 0x6d 0x61 0x00 
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/to_string/index.html b/api/basic_json/to_string/index.html index b7ddd879c..bb26c888a 100644 --- a/api/basic_json/to_string/index.html +++ b/api/basic_json/to_string/index.html @@ -28,4 +28,4 @@

Output:

{"one":1,"two":2}
 
 42
-

See also

Version history

Added in version 3.7.0.

\ No newline at end of file +

See also

Version history

Added in version 3.7.0.

\ No newline at end of file diff --git a/api/basic_json/to_ubjson/index.html b/api/basic_json/to_ubjson/index.html index 55a3916d6..783fb467f 100644 --- a/api/basic_json/to_ubjson/index.html +++ b/api/basic_json/to_ubjson/index.html @@ -76,4 +76,4 @@ [i1i2i3i4i5i6i7i8] [#i8i1i2i3i4i5i6i7i8 [$i#i812345678 -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/type/index.html b/api/basic_json/type/index.html index acf7ecec4..241624882 100644 --- a/api/basic_json/type/index.html +++ b/api/basic_json/type/index.html @@ -35,4 +35,4 @@ true true true -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/type_error/index.html b/api/basic_json/type_error/index.html index 8c6701599..0fae08369 100644 --- a/api/basic_json/type_error/index.html +++ b/api/basic_json/type_error/index.html @@ -49,4 +49,4 @@ }

Output:

message: [json.exception.type_error.308] cannot use push_back() with string
 exception id: 308
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/type_name/index.html b/api/basic_json/type_name/index.html index 87d529736..198be8d46 100644 --- a/api/basic_json/type_name/index.html +++ b/api/basic_json/type_name/index.html @@ -34,4 +34,4 @@ {"one":1,"two":2} is an object [1,2,4,8,16] is an array "Hello, world" is a string -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/unflatten/index.html b/api/basic_json/unflatten/index.html index 3642ff986..192772378 100644 --- a/api/basic_json/unflatten/index.html +++ b/api/basic_json/unflatten/index.html @@ -43,4 +43,4 @@ }, "pi": 3.141 } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/update/index.html b/api/basic_json/update/index.html index 8468624a1..07651e217 100644 --- a/api/basic_json/update/index.html +++ b/api/basic_json/update/index.html @@ -110,4 +110,4 @@ "active": true, "name": {"de": "Maus", "en": "mouse", "es": "ratón"} } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/basic_json/value/index.html b/api/basic_json/value/index.html index 54f13c0d8..b149aff3b 100644 --- a/api/basic_json/value/index.html +++ b/api/basic_json/value/index.html @@ -136,4 +136,4 @@ << " " << v_string << " " << v_boolean << "\n"; }

Output:

1 42.23 oops false
-

See also

Version history

  1. Added in version 1.0.0. Changed parameter default_value type from const ValueType& to ValueType&& in version 3.11.0.
  2. Added in version 3.11.0. Made ValueType the first template parameter in version 3.11.2.
  3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving ptr through an array unexpectedly threw out_of_range instead of returning the resolved element (or default_value, as documented).
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Changed parameter default_value type from const ValueType& to ValueType&& in version 3.11.0.
  2. Added in version 3.11.0. Made ValueType the first template parameter in version 3.11.2.
  3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving ptr through an array unexpectedly threw out_of_range instead of returning the resolved element (or default_value, as documented).
\ No newline at end of file diff --git a/api/basic_json/value_t/index.html b/api/basic_json/value_t/index.html index ea8d2b7bb..af26bf179 100644 --- a/api/basic_json/value_t/index.html +++ b/api/basic_json/value_t/index.html @@ -46,4 +46,4 @@ true true true -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/basic_json/~basic_json/index.html b/api/basic_json/~basic_json/index.html index 52ddd641b..4104429e9 100644 --- a/api/basic_json/~basic_json/index.html +++ b/api/basic_json/~basic_json/index.html @@ -1,2 +1,2 @@ (Destructor) - JSON for Modern C++
Skip to content

nlohmann::basic_json::~basic_json

~basic_json() noexcept;
-

Destroys the JSON value and frees all allocated memory.

Exception safety

No-throw guarantee: this member function never throws exceptions.

Complexity

Linear.

Version history

  • Added in version 1.0.0.
Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file +

Destroys the JSON value and frees all allocated memory.

Exception safety

No-throw guarantee: this member function never throws exceptions.

Complexity

Linear.

Version history

\ No newline at end of file diff --git a/api/byte_container_with_subtype/byte_container_with_subtype/index.html b/api/byte_container_with_subtype/byte_container_with_subtype/index.html index ec3255a48..7772966ab 100644 --- a/api/byte_container_with_subtype/byte_container_with_subtype/index.html +++ b/api/byte_container_with_subtype/byte_container_with_subtype/index.html @@ -34,4 +34,4 @@

Output:

{"bytes":[],"subtype":null}
 {"bytes":[202,254,186,190],"subtype":null}
 {"bytes":[202,254,186,190],"subtype":42}
-

Version history

Since version 3.8.0.

\ No newline at end of file +

Version history

Since version 3.8.0.

\ No newline at end of file diff --git a/api/byte_container_with_subtype/clear_subtype/index.html b/api/byte_container_with_subtype/clear_subtype/index.html index c44fc6694..5a4e9a5ef 100644 --- a/api/byte_container_with_subtype/clear_subtype/index.html +++ b/api/byte_container_with_subtype/clear_subtype/index.html @@ -22,4 +22,4 @@ }

Output:

before calling clear_subtype(): {"bytes":[202,254,186,190],"subtype":42}
 after calling clear_subtype(): {"bytes":[202,254,186,190],"subtype":null}
-

Version history

Since version 3.8.0.

\ No newline at end of file +

Version history

Since version 3.8.0.

\ No newline at end of file diff --git a/api/byte_container_with_subtype/has_subtype/index.html b/api/byte_container_with_subtype/has_subtype/index.html index 9167d6ce1..905e8a2b7 100644 --- a/api/byte_container_with_subtype/has_subtype/index.html +++ b/api/byte_container_with_subtype/has_subtype/index.html @@ -20,4 +20,4 @@ }

Output:

c1.has_subtype() = false
 c2.has_subtype() = true
-

Version history

Since version 3.8.0.

\ No newline at end of file +

Version history

Since version 3.8.0.

\ No newline at end of file diff --git a/api/byte_container_with_subtype/index.html b/api/byte_container_with_subtype/index.html index 4889929f8..8ae4dd226 100644 --- a/api/byte_container_with_subtype/index.html +++ b/api/byte_container_with_subtype/index.html @@ -1,3 +1,3 @@ Overview - JSON for Modern C++
Skip to content

nlohmann::byte_container_with_subtype

template<typename BinaryType>
 class byte_container_with_subtype : public BinaryType;
-

This type extends the template parameter BinaryType provided to basic_json with a subtype used by BSON and MessagePack. This type exists so that the user does not have to specify a type themselves with a specific naming scheme in order to override the binary type.

Template parameters

BinaryType
container to store bytes (std::vector<std::uint8_t> by default)

Member types

  • container_type - the type of the underlying container (BinaryType)
  • subtype_type - the type of the subtype (std::uint64_t)

Member functions

Version history

  • Added in version 3.8.0.
  • Changed the type of subtypes to std::uint64_t in 3.10.0.
Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file +

This type extends the template parameter BinaryType provided to basic_json with a subtype used by BSON and MessagePack. This type exists so that the user does not have to specify a type themselves with a specific naming scheme in order to override the binary type.

Template parameters

BinaryType
container to store bytes (std::vector<std::uint8_t> by default)

Member types

Member functions

Version history

\ No newline at end of file diff --git a/api/byte_container_with_subtype/set_subtype/index.html b/api/byte_container_with_subtype/set_subtype/index.html index f4570ab1f..05f2d2955 100644 --- a/api/byte_container_with_subtype/set_subtype/index.html +++ b/api/byte_container_with_subtype/set_subtype/index.html @@ -23,4 +23,4 @@ }

Output:

before calling set_subtype(42): {"bytes":[202,254,186,190],"subtype":null}
 after calling set_subtype(42): {"bytes":[202,254,186,190],"subtype":42}
-

Version history

Since version 3.8.0.

\ No newline at end of file +

Version history

Since version 3.8.0.

\ No newline at end of file diff --git a/api/byte_container_with_subtype/subtype/index.html b/api/byte_container_with_subtype/subtype/index.html index ad21aeb5e..d95304c2d 100644 --- a/api/byte_container_with_subtype/subtype/index.html +++ b/api/byte_container_with_subtype/subtype/index.html @@ -23,4 +23,4 @@ }

Output:

c1.subtype() = 18446744073709551615
 c2.subtype() = 42
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json/index.html b/api/json/index.html index 7864a5d39..f6d07e654 100644 --- a/api/json/index.html +++ b/api/json/index.html @@ -65,4 +65,4 @@ "pi": 3.141, "size": 8 } -

Version history

Since version 1.0.0.

\ No newline at end of file +

Version history

Since version 1.0.0.

\ No newline at end of file diff --git a/api/json_pointer/back/index.html b/api/json_pointer/back/index.html index ebee5fcf9..6430ab167 100644 --- a/api/json_pointer/back/index.html +++ b/api/json_pointer/back/index.html @@ -16,4 +16,4 @@ }

Output:

last reference token of "/foo" is "foo"
 last reference token of "/foo/0" is "0"
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/empty/index.html b/api/json_pointer/empty/index.html index f3a1bdcaa..bd78ebdfd 100644 --- a/api/json_pointer/empty/index.html +++ b/api/json_pointer/empty/index.html @@ -23,4 +23,4 @@ "": true "/foo": false "/foo/0": false -

Version history

Added in version 3.6.0.

\ No newline at end of file +

Version history

Added in version 3.6.0.

\ No newline at end of file diff --git a/api/json_pointer/front/index.html b/api/json_pointer/front/index.html index 1350fb337..3efde0259 100644 --- a/api/json_pointer/front/index.html +++ b/api/json_pointer/front/index.html @@ -16,4 +16,4 @@ }

Output:

first reference token of "/foo" is "foo"
 first reference token of "/foo/0" is "foo"
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/index.html b/api/json_pointer/index.html index 97f66092e..9e2c0e188 100644 --- a/api/json_pointer/index.html +++ b/api/json_pointer/index.html @@ -1,3 +1,3 @@ Overview - JSON for Modern C++
Skip to content

nlohmann::json_pointer

template<typename RefStringType>
 class json_pointer;
-

A JSON pointer defines a string syntax for identifying a specific value within a JSON document. It can be used with functions at and operator[]. Furthermore, JSON pointers are the base for JSON patches.

Template parameters

RefStringType
the string type used for the reference tokens making up the JSON pointer

Deprecation

For backwards compatibility RefStringType may also be a specialization of basic_json in which case string_t will be deduced as basic_json::string_t. This feature is deprecated and may be removed in a future major version.

Member types

  • string_t - the string type used for the reference tokens

Member functions

  • (constructor)
  • to_string - return a string representation of the JSON pointer
  • operator string_t - return a string representation of the JSON pointer
  • operator== - compare: equal
  • operator!= - compare: not equal
  • operator/= - append to the end of the JSON pointer
  • operator/ - create JSON Pointer by appending
  • parent_pointer - returns the parent of this JSON pointer
  • pop_back - remove the last reference token
  • back - return last reference token
  • push_back - append an unescaped token at the end of the pointer
  • pop_front - remove the first reference token
  • front - return first reference token
  • push_front - append an unescaped token at the start of the pointer
  • empty - return whether the pointer points to the root document

Literals

See also

Version history

  • Added in version 2.0.0.
  • Changed template parameter from basic_json to string type in version 3.11.0.
Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file +

A JSON pointer defines a string syntax for identifying a specific value within a JSON document. It can be used with functions at and operator[]. Furthermore, JSON pointers are the base for JSON patches.

Template parameters

RefStringType
the string type used for the reference tokens making up the JSON pointer

Deprecation

For backwards compatibility RefStringType may also be a specialization of basic_json in which case string_t will be deduced as basic_json::string_t. This feature is deprecated and may be removed in a future major version.

Member types

Member functions

Literals

See also

Version history

\ No newline at end of file diff --git a/api/json_pointer/json_pointer/index.html b/api/json_pointer/json_pointer/index.html index 0a778c534..680cf3770 100644 --- a/api/json_pointer/json_pointer/index.html +++ b/api/json_pointer/json_pointer/index.html @@ -49,4 +49,4 @@

Output:

[json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'foo'
 [json.exception.parse_error.108] parse error: escape character '~' must be followed with '0' or '1'
 [json.exception.parse_error.108] parse error: escape character '~' must be followed with '0' or '1'
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/operator_eq/index.html b/api/json_pointer/operator_eq/index.html index 219b5fc03..fe9aed37b 100644 --- a/api/json_pointer/operator_eq/index.html +++ b/api/json_pointer/operator_eq/index.html @@ -82,4 +82,4 @@ "" == "": true "/foo" == "/foo": true "bar" == "/foo": [json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'bar' -

Version history

  1. Added in version 2.1.0. Added C++20 member functions in version 3.11.2.
  2. Added for backward compatibility and deprecated in version 3.11.2.
\ No newline at end of file +

Version history

  1. Added in version 2.1.0. Added C++20 member functions in version 3.11.2.
  2. Added for backward compatibility and deprecated in version 3.11.2.
\ No newline at end of file diff --git a/api/json_pointer/operator_ne/index.html b/api/json_pointer/operator_ne/index.html index 6a79f10a3..ac7cfc1cd 100644 --- a/api/json_pointer/operator_ne/index.html +++ b/api/json_pointer/operator_ne/index.html @@ -72,4 +72,4 @@ "" != "": false "/foo" != "/foo": false "bar" != "/foo": [json.exception.parse_error.107] parse error at byte 1: JSON pointer must be empty or begin with '/' - was: 'bar' -

Version history

  1. Added in version 2.1.0.
  2. Added for backward compatibility and deprecated in version 3.11.2.
\ No newline at end of file +

Version history

  1. Added in version 2.1.0.
  2. Added for backward compatibility and deprecated in version 3.11.2.
\ No newline at end of file diff --git a/api/json_pointer/operator_slash/index.html b/api/json_pointer/operator_slash/index.html index 1c59008a7..39b89eed0 100644 --- a/api/json_pointer/operator_slash/index.html +++ b/api/json_pointer/operator_slash/index.html @@ -28,4 +28,4 @@

Output:

"/foo/bar/baz"
 "/foo/fob"
 "/foo/42"
-

Version history

  1. Added in version 3.6.0.
  2. Added in version 3.6.0. Changed type of token to string_t in version 3.11.0.
  3. Added in version 3.6.0.
\ No newline at end of file +

Version history

  1. Added in version 3.6.0.
  2. Added in version 3.6.0. Changed type of token to string_t in version 3.11.0.
  3. Added in version 3.6.0.
\ No newline at end of file diff --git a/api/json_pointer/operator_slasheq/index.html b/api/json_pointer/operator_slasheq/index.html index dee5b0bd0..7f5b0ad02 100644 --- a/api/json_pointer/operator_slasheq/index.html +++ b/api/json_pointer/operator_slasheq/index.html @@ -33,4 +33,4 @@ "/foo/bar/baz" "/foo/bar/baz/fob" "/foo/bar/baz/fob/42" -

Version history

  1. Added in version 3.6.0.
  2. Added in version 3.6.0. Changed type of token to string_t in version 3.11.0.
  3. Added in version 3.6.0.
\ No newline at end of file +

Version history

  1. Added in version 3.6.0.
  2. Added in version 3.6.0. Changed type of token to string_t in version 3.11.0.
  3. Added in version 3.6.0.
\ No newline at end of file diff --git a/api/json_pointer/operator_string_t/index.html b/api/json_pointer/operator_string_t/index.html index 2056a2f65..2edcd7f26 100644 --- a/api/json_pointer/operator_string_t/index.html +++ b/api/json_pointer/operator_string_t/index.html @@ -24,4 +24,4 @@ }

Output:

/foo/0
 /a~1b
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/json_pointer/parent_pointer/index.html b/api/json_pointer/parent_pointer/index.html index 777929d84..6e52ed912 100644 --- a/api/json_pointer/parent_pointer/index.html +++ b/api/json_pointer/parent_pointer/index.html @@ -20,4 +20,4 @@

Output:

parent of "" is ""
 parent of "/foo" is ""
 parent of "/foo/0" is "/foo"
-

See also

Version history

Added in version 3.6.0.

\ No newline at end of file +

See also

Version history

Added in version 3.6.0.

\ No newline at end of file diff --git a/api/json_pointer/pop_back/index.html b/api/json_pointer/pop_back/index.html index 650174eb2..e97d57903 100644 --- a/api/json_pointer/pop_back/index.html +++ b/api/json_pointer/pop_back/index.html @@ -24,4 +24,4 @@ "/foo/bar" "/foo" "" -

Version history

Added in version 3.6.0.

\ No newline at end of file +

Version history

Added in version 3.6.0.

\ No newline at end of file diff --git a/api/json_pointer/pop_front/index.html b/api/json_pointer/pop_front/index.html index 5fcece462..140137f42 100644 --- a/api/json_pointer/pop_front/index.html +++ b/api/json_pointer/pop_front/index.html @@ -24,4 +24,4 @@ "/bar/baz" "/baz" "" -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/push_back/index.html b/api/json_pointer/push_back/index.html index 44d2a7fae..ff7ca7a8f 100644 --- a/api/json_pointer/push_back/index.html +++ b/api/json_pointer/push_back/index.html @@ -26,4 +26,4 @@ "/foo" "/foo/0" "/foo/0/bar" -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/push_front/index.html b/api/json_pointer/push_front/index.html index 5dfd075aa..89ccd1a8d 100644 --- a/api/json_pointer/push_front/index.html +++ b/api/json_pointer/push_front/index.html @@ -26,4 +26,4 @@ "/foo" "/0/foo" "/bar/0/foo" -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/string_t/index.html b/api/json_pointer/string_t/index.html index d9a326d08..52c5fd714 100644 --- a/api/json_pointer/string_t/index.html +++ b/api/json_pointer/string_t/index.html @@ -14,4 +14,4 @@ }

Output:

This is a string.
 true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_pointer/to_string/index.html b/api/json_pointer/to_string/index.html index 26d718503..1acbc0ad8 100644 --- a/api/json_pointer/to_string/index.html +++ b/api/json_pointer/to_string/index.html @@ -46,4 +46,4 @@ "/k"l" "/ " "/m~0n" -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/binary/index.html b/api/json_sax/binary/index.html index 59697d670..e50bcdfab 100644 --- a/api/json_sax/binary/index.html +++ b/api/json_sax/binary/index.html @@ -116,4 +116,4 @@

Output:

binary(val=[...])
 
 result: true
-

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/boolean/index.html b/api/json_sax/boolean/index.html index cc9678a2f..13b1140a4 100644 --- a/api/json_sax/boolean/index.html +++ b/api/json_sax/boolean/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/end_array/index.html b/api/json_sax/end_array/index.html index 8fdf22fa9..5e5cc7acc 100644 --- a/api/json_sax/end_array/index.html +++ b/api/json_sax/end_array/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/end_object/index.html b/api/json_sax/end_object/index.html index c765e0fef..c1ed9ce3b 100644 --- a/api/json_sax/end_object/index.html +++ b/api/json_sax/end_object/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/index.html b/api/json_sax/index.html index 9cb0fb6ca..28f6d68fb 100644 --- a/api/json_sax/index.html +++ b/api/json_sax/index.html @@ -1,3 +1,3 @@ Overview - JSON for Modern C++
Skip to content

nlohmann::json_sax

template<typename BasicJsonType>
 struct json_sax;
-

This class describes the SAX interface used by sax_parse. Each function is called in different situations while the input is parsed. The boolean return value informs the parser whether to continue processing the input.

Template parameters

BasicJsonType
a specialization of basic_json

Member types

Member functions

  • binary (virtual) - a binary value was read
  • boolean (virtual) - a boolean value was read
  • end_array (virtual) - the end of an array was read
  • end_object (virtual) - the end of an object was read
  • key (virtual) - an object key was read
  • null (virtual) - a null value was read
  • number_float (virtual) - a floating-point number was read
  • number_integer (virtual) - an integer number was read
  • number_unsigned (virtual) - an unsigned integer number was read
  • parse_error (virtual) - a parse error occurred
  • start_array (virtual) - the beginning of an array was read
  • start_object (virtual) - the beginning of an object was read
  • string (virtual) - a string value was read

Version history

  • Added in version 3.2.0.
  • Support for binary values (binary_t, binary) added in version 3.8.0.
Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file +

This class describes the SAX interface used by sax_parse. Each function is called in different situations while the input is parsed. The boolean return value informs the parser whether to continue processing the input.

Template parameters

BasicJsonType
a specialization of basic_json

Member types

Member functions

Version history

\ No newline at end of file diff --git a/api/json_sax/key/index.html b/api/json_sax/key/index.html index a9ed8c43f..40ff241fc 100644 --- a/api/json_sax/key/index.html +++ b/api/json_sax/key/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/null/index.html b/api/json_sax/null/index.html index 7f013f400..9037d5463 100644 --- a/api/json_sax/null/index.html +++ b/api/json_sax/null/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/number_float/index.html b/api/json_sax/number_float/index.html index cdf4b9a07..ba08e8959 100644 --- a/api/json_sax/number_float/index.html +++ b/api/json_sax/number_float/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/number_integer/index.html b/api/json_sax/number_integer/index.html index dd8742fb7..0880f466c 100644 --- a/api/json_sax/number_integer/index.html +++ b/api/json_sax/number_integer/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/number_unsigned/index.html b/api/json_sax/number_unsigned/index.html index 7ccd8a331..13490c4a9 100644 --- a/api/json_sax/number_unsigned/index.html +++ b/api/json_sax/number_unsigned/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/parse_error/index.html b/api/json_sax/parse_error/index.html index ee02e5c40..9e6d6a333 100644 --- a/api/json_sax/parse_error/index.html +++ b/api/json_sax/parse_error/index.html @@ -169,4 +169,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/start_array/index.html b/api/json_sax/start_array/index.html index f048b19f0..4d9d06250 100644 --- a/api/json_sax/start_array/index.html +++ b/api/json_sax/start_array/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/start_object/index.html b/api/json_sax/start_object/index.html index 0d99bc7de..51d63cf9c 100644 --- a/api/json_sax/start_object/index.html +++ b/api/json_sax/start_object/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/json_sax/string/index.html b/api/json_sax/string/index.html index dfbd73e6a..b23a06f4f 100644 --- a/api/json_sax/string/index.html +++ b/api/json_sax/string/index.html @@ -167,4 +167,4 @@ ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input) result: false -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/index.html b/api/macros/index.html index f062a3178..026360c39 100644 --- a/api/macros/index.html +++ b/api/macros/index.html @@ -1 +1 @@ - Overview - JSON for Modern C++
Skip to content

Macros

Some aspects of the library can be configured by defining preprocessor macros before including the json.hpp header. See also the macro overview page.

Runtime assertions

Exceptions

Language support

Library version

Library namespace

Type conversions

Comparison behavior

Serialization/deserialization macros

Enums

Classes and structs

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file + Overview - JSON for Modern C++
Skip to content

Macros

Some aspects of the library can be configured by defining preprocessor macros before including the json.hpp header. See also the macro overview page.

Runtime assertions

Exceptions

Language support

Library version

Library namespace

Type conversions

Comparison behavior

Serialization/deserialization macros

Enums

Classes and structs

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file diff --git a/api/macros/json_assert/index.html b/api/macros/json_assert/index.html index fc32d774d..9f11853a0 100644 --- a/api/macros/json_assert/index.html +++ b/api/macros/json_assert/index.html @@ -24,4 +24,4 @@ auto v = j["missing"]; }

Output:

assertion error in operator[]
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_brace_init_copy_semantics/index.html b/api/macros/json_brace_init_copy_semantics/index.html index cfb639ec4..15b897934 100644 --- a/api/macros/json_brace_init_copy_semantics/index.html +++ b/api/macros/json_brace_init_copy_semantics/index.html @@ -26,4 +26,4 @@ json j{obj}; // j is {"key":"value"} -- copy of obj } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_diagnostic_positions/index.html b/api/macros/json_diagnostic_positions/index.html index 8e75a17b6..1da211495 100644 --- a/api/macros/json_diagnostic_positions/index.html +++ b/api/macros/json_diagnostic_positions/index.html @@ -165,4 +165,4 @@ Parsed string: }

Output:

[json.exception.type_error.302] (/address/housenumber) (bytes 92-95) type must be number, but is string
 
The output shows the exception with diagnostic path info and start/end positions.
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_diagnostics/index.html b/api/macros/json_diagnostics/index.html index 593f63558..598d3ed7d 100644 --- a/api/macros/json_diagnostics/index.html +++ b/api/macros/json_diagnostics/index.html @@ -75,4 +75,4 @@ } }

Output:

[json.exception.type_error.302] (bytes 92-95) type must be number, but is string
-
The output shows the exception with start/end positions only.

See also

Version history

\ No newline at end of file + The output shows the exception with start/end positions only.

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_disable_enum_serialization/index.html b/api/macros/json_disable_enum_serialization/index.html index 454643a0a..ef8ea4314 100644 --- a/api/macros/json_disable_enum_serialization/index.html +++ b/api/macros/json_disable_enum_serialization/index.html @@ -88,4 +88,4 @@ // uses user-defined from_json function Choice ch = j.get<Choice>(); } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_has_cpp_11/index.html b/api/macros/json_has_cpp_11/index.html index 1de4d2520..8f4212626 100644 --- a/api/macros/json_has_cpp_11/index.html +++ b/api/macros/json_has_cpp_11/index.html @@ -8,4 +8,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_has_filesystem/index.html b/api/macros/json_has_filesystem/index.html index 6c1793570..4d0502274 100644 --- a/api/macros/json_has_filesystem/index.html +++ b/api/macros/json_has_filesystem/index.html @@ -4,4 +4,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_has_ranges/index.html b/api/macros/json_has_ranges/index.html index fd6047293..44591addc 100644 --- a/api/macros/json_has_ranges/index.html +++ b/api/macros/json_has_ranges/index.html @@ -3,4 +3,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_has_static_rtti/index.html b/api/macros/json_has_static_rtti/index.html index feef504bc..121c70b50 100644 --- a/api/macros/json_has_static_rtti/index.html +++ b/api/macros/json_has_static_rtti/index.html @@ -3,4 +3,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_has_std_format/index.html b/api/macros/json_has_std_format/index.html index 26ee77b25..e10b11b36 100644 --- a/api/macros/json_has_std_format/index.html +++ b/api/macros/json_has_std_format/index.html @@ -3,4 +3,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_has_three_way_comparison/index.html b/api/macros/json_has_three_way_comparison/index.html index 05602e3a8..aef6198da 100644 --- a/api/macros/json_has_three_way_comparison/index.html +++ b/api/macros/json_has_three_way_comparison/index.html @@ -3,4 +3,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_no_io/index.html b/api/macros/json_no_io/index.html index 783732086..1f51b8c89 100644 --- a/api/macros/json_no_io/index.html +++ b/api/macros/json_no_io/index.html @@ -4,4 +4,4 @@ #include <nlohmann/json.hpp> ... -

Version history

\ No newline at end of file +

Version history

\ No newline at end of file diff --git a/api/macros/json_noexception/index.html b/api/macros/json_noexception/index.html index eeb19aa5c..c841181b9 100644 --- a/api/macros/json_noexception/index.html +++ b/api/macros/json_noexception/index.html @@ -4,4 +4,4 @@ #include <nlohmann/json.hpp> ... -

See also

Version history

Added in version 2.1.0.

\ No newline at end of file +

See also

Version history

Added in version 2.1.0.

\ No newline at end of file diff --git a/api/macros/json_skip_library_version_check/index.html b/api/macros/json_skip_library_version_check/index.html index 53fc11d2e..3422ae221 100644 --- a/api/macros/json_skip_library_version_check/index.html +++ b/api/macros/json_skip_library_version_check/index.html @@ -5,4 +5,4 @@ ...

Example

The following warning will be shown in case a different version of the library was already included:

Already included a different version of the library!
-

Version history

Added in version 3.11.0.

\ No newline at end of file +

Version history

Added in version 3.11.0.

\ No newline at end of file diff --git a/api/macros/json_skip_unsupported_compiler_check/index.html b/api/macros/json_skip_unsupported_compiler_check/index.html index 21d59905e..1cdda758b 100644 --- a/api/macros/json_skip_unsupported_compiler_check/index.html +++ b/api/macros/json_skip_unsupported_compiler_check/index.html @@ -4,4 +4,4 @@ #include <nlohmann/json.hpp> ... -

Version history

Added in version 3.2.0.

\ No newline at end of file +

Version history

Added in version 3.2.0.

\ No newline at end of file diff --git a/api/macros/json_throw_user/index.html b/api/macros/json_throw_user/index.html index 057b4bf7e..452e7b697 100644 --- a/api/macros/json_throw_user/index.html +++ b/api/macros/json_throw_user/index.html @@ -21,4 +21,4 @@ std::abort();} #include <nlohmann/json.hpp> -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_use_global_udls/index.html b/api/macros/json_use_global_udls/index.html index bc953af10..993207bb0 100644 --- a/api/macros/json_use_global_udls/index.html +++ b/api/macros/json_use_global_udls/index.html @@ -29,4 +29,4 @@ std::cout << j << std::endl; }

Output:

42
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_use_implicit_conversions/index.html b/api/macros/json_use_implicit_conversions/index.html index 819088435..3099841c1 100644 --- a/api/macros/json_use_implicit_conversions/index.html +++ b/api/macros/json_use_implicit_conversions/index.html @@ -4,4 +4,4 @@ std::string s = j;

When JSON_USE_IMPLICIT_CONVERSIONS is defined to 0, the code above does no longer compile. Instead, it must be written like this:

json j = "Hello, world!";
 auto s = j.get<std::string>();
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/json_use_legacy_discarded_value_comparison/index.html b/api/macros/json_use_legacy_discarded_value_comparison/index.html index 6411f177b..b654975c8 100644 --- a/api/macros/json_use_legacy_discarded_value_comparison/index.html +++ b/api/macros/json_use_legacy_discarded_value_comparison/index.html @@ -4,4 +4,4 @@ #include <nlohmann/json.hpp> ... -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/nlohmann_define_derived_type/index.html b/api/macros/nlohmann_define_derived_type/index.html index 3b82fe89f..92d40c279 100644 --- a/api/macros/nlohmann_define_derived_type/index.html +++ b/api/macros/nlohmann_define_derived_type/index.html @@ -86,4 +86,4 @@ "Ba": 23, "Bb": 42 } -

Notes:

See also

Version history

  1. Added in version 3.12.0.
  2. Added in version 3.12.0.
  3. Added in version 3.12.0.
  4. Added in version 3.12.0.
  5. Added in version 3.12.0.
  6. Added in version 3.12.0.
\ No newline at end of file +

Notes:

See also

Version history

  1. Added in version 3.12.0.
  2. Added in version 3.12.0.
  3. Added in version 3.12.0.
  4. Added in version 3.12.0.
  5. Added in version 3.12.0.
  6. Added in version 3.12.0.
\ No newline at end of file diff --git a/api/macros/nlohmann_define_type_intrusive/index.html b/api/macros/nlohmann_define_type_intrusive/index.html index 820d941ce..f8f0153e3 100644 --- a/api/macros/nlohmann_define_type_intrusive/index.html +++ b/api/macros/nlohmann_define_type_intrusive/index.html @@ -291,4 +291,4 @@ json j = p; std::cout << "serialization: " << j << std::endl; } -

See also

Version history

  1. Added in version 3.9.0.
  2. Added in version 3.11.0.
  3. Added in version 3.11.3.
\ No newline at end of file +

See also

Version history

  1. Added in version 3.9.0.
  2. Added in version 3.11.0.
  3. Added in version 3.11.3.
\ No newline at end of file diff --git a/api/macros/nlohmann_define_type_non_intrusive/index.html b/api/macros/nlohmann_define_type_non_intrusive/index.html index c9f51da01..5507895af 100644 --- a/api/macros/nlohmann_define_type_non_intrusive/index.html +++ b/api/macros/nlohmann_define_type_non_intrusive/index.html @@ -259,4 +259,4 @@ json j = p; std::cout << "serialization: " << j << std::endl; } -

See also

Version history

  1. Added in version 3.9.0.
  2. Added in version 3.11.0.
  3. Added in version 3.11.3.
\ No newline at end of file +

See also

Version history

  1. Added in version 3.9.0.
  2. Added in version 3.11.0.
  3. Added in version 3.11.3.
\ No newline at end of file diff --git a/api/macros/nlohmann_define_type_with_names/index.html b/api/macros/nlohmann_define_type_with_names/index.html index 78f2e1bf2..92f930faf 100644 --- a/api/macros/nlohmann_define_type_with_names/index.html +++ b/api/macros/nlohmann_define_type_with_names/index.html @@ -108,4 +108,4 @@ std::cout << "deserialization failed: " << e.what() << std::endl; } } -

Version history

  1. Added in version 3.13.0.
\ No newline at end of file +

Version history

  1. Added in version 3.13.0.
\ No newline at end of file diff --git a/api/macros/nlohmann_json_namespace/index.html b/api/macros/nlohmann_json_namespace/index.html index a684bafe1..763421010 100644 --- a/api/macros/nlohmann_json_namespace/index.html +++ b/api/macros/nlohmann_json_namespace/index.html @@ -14,4 +14,4 @@ std::cout << QUOTE(NLOHMANN_JSON_NAMESPACE) << std::endl; }

Output:

nlohmann::json_abi_v3_12_0
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/nlohmann_json_namespace_begin/index.html b/api/macros/nlohmann_json_namespace_begin/index.html index d7936873f..3f615463e 100644 --- a/api/macros/nlohmann_json_namespace_begin/index.html +++ b/api/macros/nlohmann_json_namespace_begin/index.html @@ -40,4 +40,4 @@ std::cout << j << std::endl; }

Output:

[1,null]
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/nlohmann_json_namespace_no_version/index.html b/api/macros/nlohmann_json_namespace_no_version/index.html index b126e8a76..d0a1952ac 100644 --- a/api/macros/nlohmann_json_namespace_no_version/index.html +++ b/api/macros/nlohmann_json_namespace_no_version/index.html @@ -14,4 +14,4 @@ std::cout << QUOTE(NLOHMANN_JSON_NAMESPACE) << std::endl; }

Output:

nlohmann::json_abi
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/macros/nlohmann_json_serialize_enum/index.html b/api/macros/nlohmann_json_serialize_enum/index.html index 16f4a2190..e6a9481c1 100644 --- a/api/macros/nlohmann_json_serialize_enum/index.html +++ b/api/macros/nlohmann_json_serialize_enum/index.html @@ -101,4 +101,4 @@

Output:

0 -> "red"
 "rot" -> 0
 "red" -> 0
-

See also

Version history

Added in version 3.4.0.

\ No newline at end of file +

See also

Version history

Added in version 3.4.0.

\ No newline at end of file diff --git a/api/macros/nlohmann_json_serialize_enum_strict/index.html b/api/macros/nlohmann_json_serialize_enum_strict/index.html index a8348bf19..3102813d7 100644 --- a/api/macros/nlohmann_json_serialize_enum_strict/index.html +++ b/api/macros/nlohmann_json_serialize_enum_strict/index.html @@ -148,4 +148,4 @@ }

Output: 

deserialization failed: [json.exception.out_of_range.410] enum value out of range for Color
 deserialization failed: [json.exception.out_of_range.410] enum value out of range for Color: "what"
-

See also

Version history

Added in version 3.13.0.

\ No newline at end of file +

See also

Version history

Added in version 3.13.0.

\ No newline at end of file diff --git a/api/macros/nlohmann_json_version_major/index.html b/api/macros/nlohmann_json_version_major/index.html index f47668e0b..997171be0 100644 --- a/api/macros/nlohmann_json_version_major/index.html +++ b/api/macros/nlohmann_json_version_major/index.html @@ -14,4 +14,4 @@ << NLOHMANN_JSON_VERSION_PATCH << std::endl; }

Output:

JSON for Modern C++ version 3.12.0
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/operator_gtgt/index.html b/api/operator_gtgt/index.html index 9a51440ba..8eb007e6c 100644 --- a/api/operator_gtgt/index.html +++ b/api/operator_gtgt/index.html @@ -38,4 +38,4 @@ "number": 23, "string": "Hello, world!" } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/operator_literal_json/index.html b/api/operator_literal_json/index.html index c69c54710..6e613a121 100644 --- a/api/operator_literal_json/index.html +++ b/api/operator_literal_json/index.html @@ -22,4 +22,4 @@ "answer": 42, "hello": "world" } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/operator_literal_json_pointer/index.html b/api/operator_literal_json_pointer/index.html index d57d73928..5e33f2a9b 100644 --- a/api/operator_literal_json_pointer/index.html +++ b/api/operator_literal_json_pointer/index.html @@ -20,4 +20,4 @@ std::cout << std::setw(2) << val << '\n'; }

Output:

"world"
-

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/api/operator_ltlt/index.html b/api/operator_ltlt/index.html index 125ec6bb6..f0940acc6 100644 --- a/api/operator_ltlt/index.html +++ b/api/operator_ltlt/index.html @@ -57,4 +57,4 @@ std::cout << ptr << std::endl; }

Output:

/foo/bar/baz
-

See also

Version history

  1. Added in version 1.0.0. Added support for indentation character and deprecated std::ostream& operator>>(const basic_json& j, std::ostream& o) in version 3.0.0.
  2. Added in version 3.11.0.
\ No newline at end of file +

See also

Version history

  1. Added in version 1.0.0. Added support for indentation character and deprecated std::ostream& operator>>(const basic_json& j, std::ostream& o) in version 3.0.0.
  2. Added in version 3.11.0.
\ No newline at end of file diff --git a/api/ordered_json/index.html b/api/ordered_json/index.html index 18ff67144..e19a74333 100644 --- a/api/ordered_json/index.html +++ b/api/ordered_json/index.html @@ -18,4 +18,4 @@ "two": 2, "three": 3 } -

See also

Version history

Since version 3.9.0.

\ No newline at end of file +

See also

Version history

Since version 3.9.0.

\ No newline at end of file diff --git a/api/ordered_map/index.html b/api/ordered_map/index.html index 945d10637..d1c5dee56 100644 --- a/api/ordered_map/index.html +++ b/api/ordered_map/index.html @@ -51,4 +51,4 @@ m_std = { one:eins three:drei two:zwei } m_ordered = { two:zwei three:drei one:eins } m_std = { one:eins three:drei two:zwei } -

See also

Version history

\ No newline at end of file +

See also

Version history

\ No newline at end of file diff --git a/community/code_of_conduct/index.html b/community/code_of_conduct/index.html index bd82f8b8c..cc8f1ab5c 100644 --- a/community/code_of_conduct/index.html +++ b/community/code_of_conduct/index.html @@ -1 +1 @@ - Code of Conduct - JSON for Modern C++
Skip to content

Contributor Covenant Code of Conduct

Our Pledge

We as members, contributors, and leaders pledge to make participation in our community a harassment-free experience for everyone, regardless of age, body size, visible or invisible disability, ethnicity, sex characteristics, gender identity and expression, level of experience, education, socio-economic status, nationality, personal appearance, race, caste, color, religion, or sexual identity and orientation.

We pledge to act and interact in ways that contribute to an open, welcoming, diverse, inclusive, and healthy community.

Our Standards

Examples of behavior that contributes to a positive environment for our community include:

  • Demonstrating empathy and kindness toward other people
  • Being respectful of differing opinions, viewpoints, and experiences
  • Giving and gracefully accepting constructive feedback
  • Accepting responsibility and apologizing to those affected by our mistakes, and learning from the experience
  • Focusing on what is best not just for us as individuals, but for the overall community

Examples of unacceptable behavior include:

  • The use of sexualized language or imagery, and sexual attention or advances of any kind
  • Trolling, insulting or derogatory comments, and personal or political attacks
  • Public or private harassment
  • Publishing others' private information, such as a physical or email address, without their explicit permission
  • Other conduct which could reasonably be considered inappropriate in a professional setting

Enforcement Responsibilities

Community leaders are responsible for clarifying and enforcing our standards of acceptable behavior and will take appropriate and fair corrective action in response to any behavior that they deem inappropriate, threatening, offensive, or harmful.

Community leaders have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, and will communicate reasons for moderation decisions when appropriate.

Scope

This Code of Conduct applies within all community spaces, and also applies when an individual is officially representing the community in public spaces. Examples of representing our community include using an official email address, posting via an official social media account, or acting as an appointed representative at an online or offline event.

Enforcement

Instances of abusive, harassing, or otherwise unacceptable behavior may be reported to the community leaders responsible for enforcement at mail@nlohmann.me. All complaints will be reviewed and investigated promptly and fairly.

All community leaders are obligated to respect the privacy and security of the reporter of any incident.

Enforcement Guidelines

Community leaders will follow these Community Impact Guidelines in determining the consequences for any action they deem in violation of this Code of Conduct:

1. Correction

Community Impact: Use of inappropriate language or other behavior deemed unprofessional or unwelcome in the community.

Consequence: A private, written warning from community leaders, providing clarity around the nature of the violation and an explanation of why the behavior was inappropriate. A public apology may be requested.

2. Warning

Community Impact: A violation through a single incident or series of actions.

Consequence: A warning with consequences for continued behavior. No interaction with the people involved, including unsolicited interaction with those enforcing the Code of Conduct, for a specified period of time. This includes avoiding interactions in community spaces as well as external channels like social media. Violating these terms may lead to a temporary or permanent ban.

3. Temporary Ban

Community Impact: A serious violation of community standards, including sustained inappropriate behavior.

Consequence: A temporary ban from any sort of interaction or public communication with the community for a specified period of time. No public or private interaction with the people involved, including unsolicited interaction with those enforcing the Code of Conduct, is allowed during this period. Violating these terms may lead to a permanent ban.

4. Permanent Ban

Community Impact: Demonstrating a pattern of violation of community standards, including sustained inappropriate behavior, harassment of an individual, or aggression toward or disparagement of classes of individuals.

Consequence: A permanent ban from any sort of public interaction within the community.

Attribution

This Code of Conduct is adapted from the Contributor Covenant, version 2.1, available at https://www.contributor-covenant.org/version/2/1/code_of_conduct.html.

Community Impact Guidelines were inspired by Mozilla's code of conduct enforcement ladder.

For answers to common questions about this code of conduct, see the FAQ at https://www.contributor-covenant.org/faq. Translations are available at https://www.contributor-covenant.org/translations.

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file + Code of Conduct - JSON for Modern C++
Skip to content

Contributor Covenant Code of Conduct

Our Pledge

We as members, contributors, and leaders pledge to make participation in our community a harassment-free experience for everyone, regardless of age, body size, visible or invisible disability, ethnicity, sex characteristics, gender identity and expression, level of experience, education, socio-economic status, nationality, personal appearance, race, caste, color, religion, or sexual identity and orientation.

We pledge to act and interact in ways that contribute to an open, welcoming, diverse, inclusive, and healthy community.

Our Standards

Examples of behavior that contributes to a positive environment for our community include:

  • Demonstrating empathy and kindness toward other people
  • Being respectful of differing opinions, viewpoints, and experiences
  • Giving and gracefully accepting constructive feedback
  • Accepting responsibility and apologizing to those affected by our mistakes, and learning from the experience
  • Focusing on what is best not just for us as individuals, but for the overall community

Examples of unacceptable behavior include:

  • The use of sexualized language or imagery, and sexual attention or advances of any kind
  • Trolling, insulting or derogatory comments, and personal or political attacks
  • Public or private harassment
  • Publishing others' private information, such as a physical or email address, without their explicit permission
  • Other conduct which could reasonably be considered inappropriate in a professional setting

Enforcement Responsibilities

Community leaders are responsible for clarifying and enforcing our standards of acceptable behavior and will take appropriate and fair corrective action in response to any behavior that they deem inappropriate, threatening, offensive, or harmful.

Community leaders have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, and will communicate reasons for moderation decisions when appropriate.

Scope

This Code of Conduct applies within all community spaces, and also applies when an individual is officially representing the community in public spaces. Examples of representing our community include using an official email address, posting via an official social media account, or acting as an appointed representative at an online or offline event.

Enforcement

Instances of abusive, harassing, or otherwise unacceptable behavior may be reported to the community leaders responsible for enforcement at mail@nlohmann.me. All complaints will be reviewed and investigated promptly and fairly.

All community leaders are obligated to respect the privacy and security of the reporter of any incident.

Enforcement Guidelines

Community leaders will follow these Community Impact Guidelines in determining the consequences for any action they deem in violation of this Code of Conduct:

1. Correction

Community Impact: Use of inappropriate language or other behavior deemed unprofessional or unwelcome in the community.

Consequence: A private, written warning from community leaders, providing clarity around the nature of the violation and an explanation of why the behavior was inappropriate. A public apology may be requested.

2. Warning

Community Impact: A violation through a single incident or series of actions.

Consequence: A warning with consequences for continued behavior. No interaction with the people involved, including unsolicited interaction with those enforcing the Code of Conduct, for a specified period of time. This includes avoiding interactions in community spaces as well as external channels like social media. Violating these terms may lead to a temporary or permanent ban.

3. Temporary Ban

Community Impact: A serious violation of community standards, including sustained inappropriate behavior.

Consequence: A temporary ban from any sort of interaction or public communication with the community for a specified period of time. No public or private interaction with the people involved, including unsolicited interaction with those enforcing the Code of Conduct, is allowed during this period. Violating these terms may lead to a permanent ban.

4. Permanent Ban

Community Impact: Demonstrating a pattern of violation of community standards, including sustained inappropriate behavior, harassment of an individual, or aggression toward or disparagement of classes of individuals.

Consequence: A permanent ban from any sort of public interaction within the community.

Attribution

This Code of Conduct is adapted from the Contributor Covenant, version 2.1, available at https://www.contributor-covenant.org/version/2/1/code_of_conduct.html.

Community Impact Guidelines were inspired by Mozilla's code of conduct enforcement ladder.

For answers to common questions about this code of conduct, see the FAQ at https://www.contributor-covenant.org/faq. Translations are available at https://www.contributor-covenant.org/translations.

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file diff --git a/community/contribution_guidelines/index.html b/community/contribution_guidelines/index.html index e63205bf1..759f77564 100644 --- a/community/contribution_guidelines/index.html +++ b/community/contribution_guidelines/index.html @@ -5,4 +5,4 @@ $ ctest --test-dir

Add tests

The tests are located in tests/src/unit-*.cpp and contain doctest assertions like CHECK. The tests are structured along the features of the library or the nature of the tests. Usually, it should be clear from the context which existing file needs to be extended, and only very few cases require creating new test files.

When fixing a bug, edit unit-regression2.cpp and add a section referencing the fixed issue.

Exceptions

When you test exceptions, please use CHECK_THROWS_WITH_AS which also takes the what() argument of the thrown exception into account.

Coverage

If test coverage decreases, an automatic warning comment will be posted on the pull request. You can access a code coverage report as an artifact to the “Ubuntu” workflow.

Update the documentation

The main documentation of the library is generated from the files docs/mkdocs/docs. This folder contains dedicated pages for certain features, a list of all exceptions, and extensive API documentation with details on every public API function.

Build the documentation locally using:

make install_venv -C docs/mkdocs
 make serve -C docs/mkdocs

The documentation will then be available at http://127.0.0.1:8000/. See the documentation of mkdocs and Material for MkDocs for more information.

Amalgamate the source code

The single-header files single_include/nlohmann/json.hpp and single_include/nlohmann/json_fwd.hpp are generated from the source files in the include/nlohmann directory. Do not edit the files directly; instead, modify the include/nlohmann sources and regenerate the files by executing:

make amalgamate
-

Running make amalgamate will also apply automatic formatting to the source files using Artistic Style. This formatting may modify your source files in-place. Be certain to review and commit any changes to avoid unintended formatting diffs in commits.

Please don't...

Certain contributions are not helpful.

Break the public API

We take pride in the library being used by numerous customers across various industries. They all rely on the guarantees provided by semantic versioning. Please do not change the library such that the public API of the 3.x.y version is broken. This includes:

Although these guidelines may seem restrictive, they are essential for maintaining the library’s utility.

Breaking changes may be introduced when they are guarded with a feature macro such as JSON_USE_IMPLICIT_CONVERSIONS which allows selectively changing the behavior of the library. In next steps, the current behavior can then be deprecated. Using feature macros then allows users to test their code against the library in the next major release.

Break C++11 language conformance

This library is designed to work with C++11 and later. This means that any supported C++11 compiler should compile the library without problems. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support.

Please do not add features that do not work with the mentioned supported compilers. Please guard features from C++14 and later against the respective JSON_HAS_CPP_14 macros.

Break JSON conformance

Please refrain from proposing changes that would break JSON conformance. If you propose a conformant extension of JSON to be supported by the library, please motivate this extension.

Wanted

The following areas really need contribution and are always welcomed:

We look forward to your contributions and collaboration to enhance the library!

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file +

Running make amalgamate will also apply automatic formatting to the source files using Artistic Style. This formatting may modify your source files in-place. Be certain to review and commit any changes to avoid unintended formatting diffs in commits.

Please don't...

Certain contributions are not helpful.

Break the public API

We take pride in the library being used by numerous customers across various industries. They all rely on the guarantees provided by semantic versioning. Please do not change the library such that the public API of the 3.x.y version is broken. This includes:

Although these guidelines may seem restrictive, they are essential for maintaining the library’s utility.

Breaking changes may be introduced when they are guarded with a feature macro such as JSON_USE_IMPLICIT_CONVERSIONS which allows selectively changing the behavior of the library. In next steps, the current behavior can then be deprecated. Using feature macros then allows users to test their code against the library in the next major release.

Break C++11 language conformance

This library is designed to work with C++11 and later. This means that any supported C++11 compiler should compile the library without problems. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support.

Please do not add features that do not work with the mentioned supported compilers. Please guard features from C++14 and later against the respective JSON_HAS_CPP_14 macros.

Break JSON conformance

Please refrain from proposing changes that would break JSON conformance. If you propose a conformant extension of JSON to be supported by the library, please motivate this extension.

Wanted

The following areas really need contribution and are always welcomed:

We look forward to your contributions and collaboration to enhance the library!

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file diff --git a/community/governance/index.html b/community/governance/index.html index 25603eb46..bd2554e3e 100644 --- a/community/governance/index.html +++ b/community/governance/index.html @@ -1 +1 @@ - Governance - JSON for Modern C++
Skip to content

Governance

The governance model for the JSON for Modern C++ project is a Benevolent Dictator for Life (BDFL) structure. As the sole maintainer, Niels Lohmann is responsible for all key aspects of the project. The project governance may evolve as the project grows, but any changes will be documented here and communicated to contributors.

Overview

This project is led by a benevolent dictator, Niels Lohmann, and managed by the community. That is, the community actively contributes to the day-to-day maintenance of the project, but the general strategic line is drawn by the benevolent dictator. In case of disagreement, they have the last word. It is the benevolent dictator’s job to resolve disputes within the community and to ensure that the project is able to progress in a coordinated way. In turn, it is the community’s job to guide the decisions of the benevolent dictator through active engagement and contribution.

Roles and responsibilities

Benevolent dictator (project lead)

Typically, the benevolent dictator, or project lead, is self-appointed. However, because the community always has the ability to fork, this person is fully answerable to the community. The project lead’s role is a difficult one: they set the strategic objectives of the project and communicate these clearly to the community. They also have to understand the community as a whole and strive to satisfy as many conflicting needs as possible, while ensuring that the project survives in the long term.

In many ways, the role of the benevolent dictator is less about dictatorship and more about diplomacy. The key is to ensure that, as the project expands, the right people are given influence over it and the community rallies behind the vision of the project lead. The lead’s job is then to ensure that the committers (see below) make the right decisions on behalf of the project. Generally speaking, as long as the committers are aligned with the project’s strategy, the project lead will allow them to proceed as they desire.

Committers

Committers are contributors who have made several valuable contributions to the project and are now relied upon to both write code directly to the repository and screen the contributions of others. In many cases they are programmers but it is also possible that they contribute in a different role. Typically, a committer will focus on a specific aspect of the project, and will bring a level of expertise and understanding that earns them the respect of the community and the project lead. The role of committer is not an official one, it is simply a position that influential members of the community will find themselves in as the project lead looks to them for guidance and support.

Committers have no authority over the overall direction of the project. However, they do have the ear of the project lead. It is a committer’s job to ensure that the lead is aware of the community’s needs and collective objectives, and to help develop or elicit appropriate contributions to the project. Often, committers are given informal control over their specific areas of responsibility, and are assigned rights to directly modify certain areas of the source code. That is, although committers do not have explicit decision-making authority, they will often find that their actions are synonymous with the decisions made by the lead.

Contributors

Contributors are community members who either have no desire to become committers, or have not yet been given the opportunity by the benevolent dictator. They make valuable contributions, such as those outlined in the list below, but generally do not have the authority to make direct changes to the project code. Contributors engage with the project through communication tools, such as email lists, and via reports and patches attached to issues in the issue tracker, as detailed in our community tools document.

Anyone can become a contributor. There is no expectation of commitment to the project, no specific skill requirements and no selection process. To become a contributor, a community member simply has to perform one or more actions that are beneficial to the project.

Some contributors will already be engaging with the project as users, but will also find themselves doing one or more of the following:

  • supporting new users (current users often provide the most effective new user support)
  • reporting bugs
  • identifying requirements
  • supplying graphics and web design
  • programming
  • assisting with project infrastructure
  • writing documentation
  • fixing bugs
  • adding features

As contributors gain experience and familiarity with the project, they may find that the project lead starts relying on them more and more. When this begins to happen, they gradually adopt the role of committer, as described above.

Users

Users are community members who have a need for the project. They are the most important members of the community: without them, the project would have no purpose. Anyone can be a user; there are no specific requirements.

Users should be encouraged to participate in the life of the project and the community as much as possible. User contributions enable the project team to ensure that they are satisfying the needs of those users. Common user activities include (but are not limited to):

  • evangelising about the project
  • informing developers of project strengths and weaknesses from a new user’s perspective
  • providing moral support (a ‘thank you’ goes a long way)
  • providing financial support

Users who continue to engage with the project and its community will often find themselves becoming more and more involved. Such users may then go on to become contributors, as described above.

Support

All participants in the community are encouraged to provide support for new users within the project management infrastructure. This support is provided as a way of growing the community. Those seeking support should recognise that all support activity within the project is voluntary and is therefore provided as and when time allows. A user requiring guaranteed response times or results should therefore seek to purchase a support contract from a vendor. (Of course, that vendor should be an active member of the community.) However, for those willing to engage with the project on its own terms, and willing to help support other users, the community support channels are ideal.

Contribution Process

Anyone can contribute to the project, regardless of their skills, as there are many ways to contribute. For instance, a contributor might be active on the project mailing list and issue tracker, or might supply patches. The various ways of contributing are described in more detail in our roles in open source document.

The developer mailing list is the most appropriate place for a contributor to ask for help when making their first contribution.

Decision-Making Process

The benevolent dictatorship model does not need a formal conflict resolution process, since the project lead’s word is final. If the community chooses to question the wisdom of the actions of a committer, the project lead can review their decisions by checking the email archives, and either uphold or reverse them.

Source

The text was taken from http://oss-watch.ac.uk/resources/benevolentdictatorgovernancemodel.

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file + Governance - JSON for Modern C++
Skip to content

Governance

The governance model for the JSON for Modern C++ project is a Benevolent Dictator for Life (BDFL) structure. As the sole maintainer, Niels Lohmann is responsible for all key aspects of the project. The project governance may evolve as the project grows, but any changes will be documented here and communicated to contributors.

Overview

This project is led by a benevolent dictator, Niels Lohmann, and managed by the community. That is, the community actively contributes to the day-to-day maintenance of the project, but the general strategic line is drawn by the benevolent dictator. In case of disagreement, they have the last word. It is the benevolent dictator’s job to resolve disputes within the community and to ensure that the project is able to progress in a coordinated way. In turn, it is the community’s job to guide the decisions of the benevolent dictator through active engagement and contribution.

Roles and responsibilities

Benevolent dictator (project lead)

Typically, the benevolent dictator, or project lead, is self-appointed. However, because the community always has the ability to fork, this person is fully answerable to the community. The project lead’s role is a difficult one: they set the strategic objectives of the project and communicate these clearly to the community. They also have to understand the community as a whole and strive to satisfy as many conflicting needs as possible, while ensuring that the project survives in the long term.

In many ways, the role of the benevolent dictator is less about dictatorship and more about diplomacy. The key is to ensure that, as the project expands, the right people are given influence over it and the community rallies behind the vision of the project lead. The lead’s job is then to ensure that the committers (see below) make the right decisions on behalf of the project. Generally speaking, as long as the committers are aligned with the project’s strategy, the project lead will allow them to proceed as they desire.

Committers

Committers are contributors who have made several valuable contributions to the project and are now relied upon to both write code directly to the repository and screen the contributions of others. In many cases they are programmers but it is also possible that they contribute in a different role. Typically, a committer will focus on a specific aspect of the project, and will bring a level of expertise and understanding that earns them the respect of the community and the project lead. The role of committer is not an official one, it is simply a position that influential members of the community will find themselves in as the project lead looks to them for guidance and support.

Committers have no authority over the overall direction of the project. However, they do have the ear of the project lead. It is a committer’s job to ensure that the lead is aware of the community’s needs and collective objectives, and to help develop or elicit appropriate contributions to the project. Often, committers are given informal control over their specific areas of responsibility, and are assigned rights to directly modify certain areas of the source code. That is, although committers do not have explicit decision-making authority, they will often find that their actions are synonymous with the decisions made by the lead.

Contributors

Contributors are community members who either have no desire to become committers, or have not yet been given the opportunity by the benevolent dictator. They make valuable contributions, such as those outlined in the list below, but generally do not have the authority to make direct changes to the project code. Contributors engage with the project through communication tools, such as email lists, and via reports and patches attached to issues in the issue tracker, as detailed in our community tools document.

Anyone can become a contributor. There is no expectation of commitment to the project, no specific skill requirements and no selection process. To become a contributor, a community member simply has to perform one or more actions that are beneficial to the project.

Some contributors will already be engaging with the project as users, but will also find themselves doing one or more of the following:

  • supporting new users (current users often provide the most effective new user support)
  • reporting bugs
  • identifying requirements
  • supplying graphics and web design
  • programming
  • assisting with project infrastructure
  • writing documentation
  • fixing bugs
  • adding features

As contributors gain experience and familiarity with the project, they may find that the project lead starts relying on them more and more. When this begins to happen, they gradually adopt the role of committer, as described above.

Users

Users are community members who have a need for the project. They are the most important members of the community: without them, the project would have no purpose. Anyone can be a user; there are no specific requirements.

Users should be encouraged to participate in the life of the project and the community as much as possible. User contributions enable the project team to ensure that they are satisfying the needs of those users. Common user activities include (but are not limited to):

  • evangelising about the project
  • informing developers of project strengths and weaknesses from a new user’s perspective
  • providing moral support (a ‘thank you’ goes a long way)
  • providing financial support

Users who continue to engage with the project and its community will often find themselves becoming more and more involved. Such users may then go on to become contributors, as described above.

Support

All participants in the community are encouraged to provide support for new users within the project management infrastructure. This support is provided as a way of growing the community. Those seeking support should recognise that all support activity within the project is voluntary and is therefore provided as and when time allows. A user requiring guaranteed response times or results should therefore seek to purchase a support contract from a vendor. (Of course, that vendor should be an active member of the community.) However, for those willing to engage with the project on its own terms, and willing to help support other users, the community support channels are ideal.

Contribution Process

Anyone can contribute to the project, regardless of their skills, as there are many ways to contribute. For instance, a contributor might be active on the project mailing list and issue tracker, or might supply patches. The various ways of contributing are described in more detail in our roles in open source document.

The developer mailing list is the most appropriate place for a contributor to ask for help when making their first contribution.

Decision-Making Process

The benevolent dictatorship model does not need a formal conflict resolution process, since the project lead’s word is final. If the community chooses to question the wisdom of the actions of a committer, the project lead can review their decisions by checking the email archives, and either uphold or reverse them.

Source

The text was taken from http://oss-watch.ac.uk/resources/benevolentdictatorgovernancemodel.

Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file diff --git a/community/index.html b/community/index.html index 51ed3bb46..cd94febb4 100644 --- a/community/index.html +++ b/community/index.html @@ -1 +1 @@ - Community - JSON for Modern C++
Skip to content
Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file + Community - JSON for Modern C++
Skip to content
Copyright © 2013-2026 Niels Lohmann
\ No newline at end of file diff --git a/community/quality_assurance/index.html b/community/quality_assurance/index.html index 5435cbe16..3ba172e02 100644 --- a/community/quality_assurance/index.html +++ b/community/quality_assurance/index.html @@ -548,4 +548,4 @@ # for the linux (LF) line end style --lineend=linux -

  • The code style is checked with cpplint with 61 enabled rules.

    • Simple integration

    Requirement: Single header

    The library can be used by adding a single header to a C++ project.

    Requirement: CMake as primary development tool

    All library functions are exposed and usable by CMake.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

  • The code style is checked with cpplint with 61 enabled rules.

    • Simple integration

    Requirement: Single header

    The library can be used by adding a single header to a C++ project.

    Requirement: CMake as primary development tool

    All library functions are exposed and usable by CMake.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/community/security_policy/index.html b/community/security_policy/index.html index 0c039c421..b4c8afc2d 100644 --- a/community/security_policy/index.html +++ b/community/security_policy/index.html @@ -1 +1 @@ - Security Policy - JSON for Modern C++
    Skip to content

    Security Policy

    Reporting a Vulnerability

    We value the security of our users and appreciate your efforts to responsibly disclose vulnerabilities. If you have identified a security vulnerability in this repository, please use the GitHub Security Advisory "Report a Vulnerability" tab.

    Until it is published, this draft security advisory will only be visible to the maintainers of this project. Other users and teams may be added once the advisory is created.

    We will send a response indicating the next steps in handling your report. After the initial reply to your report, we will keep you informed of the progress towards a fix and full announcement and may ask for additional information or guidance.

    For vulnerabilities in third-party dependencies or modules, please report them directly to the respective maintainers.

    Additional Resources

    We sincerely thank you for contributing to the security and integrity of this project!

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Security Policy - JSON for Modern C++
    Skip to content

    Security Policy

    Reporting a Vulnerability

    We value the security of our users and appreciate your efforts to responsibly disclose vulnerabilities. If you have identified a security vulnerability in this repository, please use the GitHub Security Advisory "Report a Vulnerability" tab.

    Until it is published, this draft security advisory will only be visible to the maintainers of this project. Other users and teams may be added once the advisory is created.

    We will send a response indicating the next steps in handling your report. After the initial reply to your report, we will keep you informed of the progress towards a fix and full announcement and may ask for additional information or guidance.

    For vulnerabilities in third-party dependencies or modules, please report them directly to the respective maintainers.

    Additional Resources

    We sincerely thank you for contributing to the security and integrity of this project!

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/arbitrary_types/index.html b/features/arbitrary_types/index.html index dac8d240f..59685904c 100644 --- a/features/arbitrary_types/index.html +++ b/features/arbitrary_types/index.html @@ -179,4 +179,4 @@ value = j.template get<T>(); // oops! } }; -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/assertions/index.html b/features/assertions/index.html index 824b99674..e9260bc6c 100644 --- a/features/assertions/index.html +++ b/features/assertions/index.html @@ -43,4 +43,4 @@ } }

    Output:

    [json.exception.parse_error.101] parse error: attempting to parse an empty input; check that your input string or stream contains the expected JSON
-

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_formats/bjdata/index.html b/features/binary_formats/bjdata/index.html index da1897c8e..75057a08e 100644 --- a/features/binary_formats/bjdata/index.html +++ b/features/binary_formats/bjdata/index.html @@ -95,4 +95,4 @@ "compact": true, "schema": 0 } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_formats/bson/index.html b/features/binary_formats/bson/index.html index ce2865156..84fdbb6e1 100644 --- a/features/binary_formats/bson/index.html +++ b/features/binary_formats/bson/index.html @@ -46,4 +46,4 @@ "compact": true, "schema": 0 } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_formats/cbor/index.html b/features/binary_formats/cbor/index.html index cc4d3dfee..af8d36c66 100644 --- a/features/binary_formats/cbor/index.html +++ b/features/binary_formats/cbor/index.html @@ -45,4 +45,4 @@ "compact": true, "schema": 0 } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_formats/index.html b/features/binary_formats/index.html index b5a924384..42bf2f528 100644 --- a/features/binary_formats/index.html +++ b/features/binary_formats/index.html @@ -1 +1 @@ - Binary Formats - JSON for Modern C++
    Skip to content

    Binary Formats

    Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance, over a network. Hence, the library supports

    to efficiently encode JSON values to byte vectors and to decode such vectors.

    Comparison

    Completeness

    Format Serialization Deserialization
    BJData complete complete
    BSON incomplete: top-level value must be an object incomplete, but all JSON types are supported
    CBOR complete incomplete, but all JSON types are supported
    MessagePack complete complete
    UBJSON complete complete

    Binary values

    Format Binary values Binary subtypes
    BJData not supported not supported
    BSON supported supported
    CBOR supported supported
    MessagePack supported supported
    UBJSON not supported not supported

    See binary values for more information.

    Sizes

    Format canada.json twitter.json citm_catalog.json jeopardy.json
    BJData 53.2 % 91.1 % 78.1 % 96.6 %
    BJData (size) 58.6 % 92.1 % 86.7 % 97.4 %
    BJData (size+type) 58.6 % 92.1 % 86.5 % 97.4 %
    BSON 85.8 % 95.2 % 95.8 % 106.7 %
    CBOR 50.5 % 86.3 % 68.4 % 88.0 %
    MessagePack 50.5 % 86.0 % 68.5 % 87.9 %
    UBJSON 53.2 % 91.3 % 78.2 % 96.6 %
    UBJSON (size) 58.6 % 92.3 % 86.8 % 97.4 %
    UBJSON (size+type) 55.9 % 92.3 % 85.0 % 95.0 %

    Sizes compared to minified JSON value.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Binary Formats - JSON for Modern C++
    Skip to content

    Binary Formats

    Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance, over a network. Hence, the library supports

    to efficiently encode JSON values to byte vectors and to decode such vectors.

    Comparison

    Completeness

    Format Serialization Deserialization
    BJData complete complete
    BSON incomplete: top-level value must be an object incomplete, but all JSON types are supported
    CBOR complete incomplete, but all JSON types are supported
    MessagePack complete complete
    UBJSON complete complete

    Binary values

    Format Binary values Binary subtypes
    BJData not supported not supported
    BSON supported supported
    CBOR supported supported
    MessagePack supported supported
    UBJSON not supported not supported

    See binary values for more information.

    Sizes

    Format canada.json twitter.json citm_catalog.json jeopardy.json
    BJData 53.2 % 91.1 % 78.1 % 96.6 %
    BJData (size) 58.6 % 92.1 % 86.7 % 97.4 %
    BJData (size+type) 58.6 % 92.1 % 86.5 % 97.4 %
    BSON 85.8 % 95.2 % 95.8 % 106.7 %
    CBOR 50.5 % 86.3 % 68.4 % 88.0 %
    MessagePack 50.5 % 86.0 % 68.5 % 87.9 %
    UBJSON 53.2 % 91.3 % 78.2 % 96.6 %
    UBJSON (size) 58.6 % 92.3 % 86.8 % 97.4 %
    UBJSON (size+type) 55.9 % 92.3 % 85.0 % 95.0 %

    Sizes compared to minified JSON value.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_formats/messagepack/index.html b/features/binary_formats/messagepack/index.html index b7fcd7abc..b58c3af63 100644 --- a/features/binary_formats/messagepack/index.html +++ b/features/binary_formats/messagepack/index.html @@ -45,4 +45,4 @@ "compact": true, "schema": 0 } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_formats/ubjson/index.html b/features/binary_formats/ubjson/index.html index e5a2583fd..f7fe5ac3b 100644 --- a/features/binary_formats/ubjson/index.html +++ b/features/binary_formats/ubjson/index.html @@ -90,4 +90,4 @@ "compact": true, "schema": 0 } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/binary_values/index.html b/features/binary_values/index.html index 0951d7615..085b009b2 100644 --- a/features/binary_values/index.html +++ b/features/binary_values/index.html @@ -154,4 +154,4 @@ vector <|-- binary_t

    By default, binary values are stored as

    Note that subtype (42) is not serialized and that UBJSON has no binary type, and deserializing v would yield the following value:

    {
   "binary": [202, 254, 186, 190]
 }
-
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/comments/index.html b/features/comments/index.html index d0580cd7e..53dcf0f0c 100644 --- a/features/comments/index.html +++ b/features/comments/index.html @@ -45,4 +45,4 @@ "Neptune" ] } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/conversions.md b/features/conversions.md index eaa213324..7f63587fd 100644 --- a/features/conversions.md +++ b/features/conversions.md @@ -66,6 +66,24 @@ which forces the explicit `get` form and can catch unintended conversions at com floating-point value as an integer truncates it, and narrowing conversions may overflow. See [number conversion](types/number_handling.md#number-conversion) for details and how to guard against it. +!!! warning "std::optional direct construction from JSON null throws" + + Constructing or assigning `std::optional` directly from a JSON value does not correctly produce + `std::nullopt` for a JSON `null`: + + ```cpp + json j_null; + std::optional opt = j_null; // ❌ throws type_error 302 + ``` + + This is due to C++ language rules: `std::optional` has its own converting constructor that is chosen over + `basic_json::operator T()` when both are viable. Use `get>()` or `get_to()` instead: + + ```cpp + auto opt = j_null.get>(); // ✅ std::nullopt + j_null.get_to(opt); // ✅ std::nullopt + ``` + ## Putting values in The reverse direction works the same way: assigning or constructing a `json` from a C++ value converts it to JSON. diff --git a/features/conversions/index.html b/features/conversions/index.html index 46c6cde87..7e6b0d0b4 100644 --- a/features/conversions/index.html +++ b/features/conversions/index.html @@ -77,6 +77,10 @@ auto m = j.get<std::map<std::string, int>>(); // {{"one", 1}, {"two", 2}}

    Implicit conversions

    By default, a JSON value implicitly converts to a compatible C++ type, so the explicit get call can often be omitted:

    json j = "Hello";
 std::string s = j;   // implicit conversion, same as j.get<std::string>()
-

    Implicit conversions are convenient but can be surprising (for example, in overload resolution or with auto). They can be disabled by defining JSON_USE_IMPLICIT_CONVERSIONS to 0, which forces the explicit get form and can catch unintended conversions at compile time.

    Conversions do not range-check numbers

    Just like C++ itself, the get family performs numeric conversions without range checks — retrieving a floating-point value as an integer truncates it, and narrowing conversions may overflow. See number conversion for details and how to guard against it.

    Putting values in

    The reverse direction works the same way: assigning or constructing a json from a C++ value converts it to JSON.

    std::vector<int> numbers = {1, 2, 3};
+

    Implicit conversions are convenient but can be surprising (for example, in overload resolution or with auto). They can be disabled by defining JSON_USE_IMPLICIT_CONVERSIONS to 0, which forces the explicit get form and can catch unintended conversions at compile time.

    Conversions do not range-check numbers

    Just like C++ itself, the get family performs numeric conversions without range checks — retrieving a floating-point value as an integer truncates it, and narrowing conversions may overflow. See number conversion for details and how to guard against it.

    std::optional direct construction from JSON null throws

    Constructing or assigning std::optional<T> directly from a JSON value does not correctly produce std::nullopt for a JSON null:

    json j_null;
+std::optional<std::string> opt = j_null;  // ❌ throws type_error 302
+

    This is due to C++ language rules: std::optional<T> has its own converting constructor that is chosen over basic_json::operator T() when both are viable. Use get<std::optional<T>>() or get_to() instead:

    auto opt = j_null.get<std::optional<std::string>>();  // ✅ std::nullopt
+j_null.get_to(opt);                                     // ✅ std::nullopt
+

    Putting values in

    The reverse direction works the same way: assigning or constructing a json from a C++ value converts it to JSON.

    std::vector<int> numbers = {1, 2, 3};
 json j = numbers;   // [1,2,3]
-

    Your own types

    The conversions above are built in for standard types. To make the same syntax work for your own types, provide to_json/from_json functions (or use one of the convenience macros). This is described in detail on the arbitrary types conversions page. Enums can be mapped to strings as described in specializing enum conversion.

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Your own types

    The conversions above are built in for standard types. To make the same syntax work for your own types, provide to_json/from_json functions (or use one of the convenience macros). This is described in detail on the arbitrary types conversions page. Enums can be mapped to strings as described in specializing enum conversion.

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/conversions/index.md b/features/conversions/index.md index d9f07d0c5..595be1359 100644 --- a/features/conversions/index.md +++ b/features/conversions/index.md @@ -122,6 +122,22 @@ Conversions do not range-check numbers Just like C++ itself, the `get` family performs numeric conversions without range checks — retrieving a floating-point value as an integer truncates it, and narrowing conversions may overflow. See [number conversion](https://json.nlohmann.me/features/types/number_handling/#number-conversion) for details and how to guard against it. +std::optional direct construction from JSON null throws + +Constructing or assigning `std::optional` directly from a JSON value does not correctly produce `std::nullopt` for a JSON `null`: + +``` +json j_null; +std::optional opt = j_null; // ❌ throws type_error 302 +``` + +This is due to C++ language rules: `std::optional` has its own converting constructor that is chosen over `basic_json::operator T()` when both are viable. Use `get>()` or `get_to()` instead: + +``` +auto opt = j_null.get>(); // ✅ std::nullopt +j_null.get_to(opt); // ✅ std::nullopt +``` + ## Putting values in The reverse direction works the same way: assigning or constructing a `json` from a C++ value converts it to JSON. diff --git a/features/creating_values/index.html b/features/creating_values/index.html index ec69abbd7..674daff45 100644 --- a/features/creating_values/index.html +++ b/features/creating_values/index.html @@ -42,4 +42,4 @@ "answer": 42, "hello": "world" } -

    Note this parses the string, so "42"_json is the number 42, whereas json("42") is the JSON string "42".

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Note this parses the string, so "42"_json is the number 42, whereas json("42") is the JSON string "42".

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/element_access/checked_access/index.html b/features/element_access/checked_access/index.html index f54ea299e..70fc636a4 100644 --- a/features/element_access/checked_access/index.html +++ b/features/element_access/checked_access/index.html @@ -12,4 +12,4 @@

    When accessing an invalid index (i.e., an index greater than or equal to the array size) or the passed object key is non-existing, an exception is thrown.

    Accessing via invalid index or missing key 
    j.at("hobbies").at(3) = "cooking";

    This code produces the following exception:

    [json.exception.out_of_range.401] array index 3 is out of range

    When extended diagnostic messages are enabled by defining JSON_DIAGNOSTICS, the exception further gives information where the key or index is missing or out of range.

    [json.exception.out_of_range.401] (/hobbies) array index 3 is out of range
-

    Notes

    Exceptions

    • at can only be used with objects (with a string argument) or with arrays (with a numeric argument). For other types, a basic_json::type_error is thrown.
    • basic_json::out_of_range exception exceptions are thrown if the provided key is not found in an object or the provided index is invalid.

    Summary

    scenario non-const value const value
    access to existing object key reference to existing value is returned const reference to existing value is returned
    access to valid array index reference to existing value is returned const reference to existing value is returned
    access to non-existing object key basic_json::out_of_range exception is thrown basic_json::out_of_range exception is thrown
    access to invalid array index basic_json::out_of_range exception is thrown basic_json::out_of_range exception is thrown
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Notes

    Exceptions

    • at can only be used with objects (with a string argument) or with arrays (with a numeric argument). For other types, a basic_json::type_error is thrown.
    • basic_json::out_of_range exception exceptions are thrown if the provided key is not found in an object or the provided index is invalid.

    Summary

    scenario non-const value const value
    access to existing object key reference to existing value is returned const reference to existing value is returned
    access to valid array index reference to existing value is returned const reference to existing value is returned
    access to non-existing object key basic_json::out_of_range exception is thrown basic_json::out_of_range exception is thrown
    access to invalid array index basic_json::out_of_range exception is thrown basic_json::out_of_range exception is thrown
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/element_access/default_value/index.html b/features/element_access/default_value/index.html index 81e277bc4..e0eff7afd 100644 --- a/features/element_access/default_value/index.html +++ b/features/element_access/default_value/index.html @@ -20,4 +20,4 @@ default value (int): -1 default value (uint64_t): 18446744073709551615 explicit return value type: 18446744073709551615 -

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/element_access/index.html b/features/element_access/index.html index 919855542..36b12bfa0 100644 --- a/features/element_access/index.html +++ b/features/element_access/index.html @@ -1 +1 @@ - Element Access - JSON for Modern C++

    Element Access

    There are many ways elements in a JSON value can be accessed:

    • unchecked access via operator[]
    • checked access via at
    • access with default value via value
    • iterators
    • JSON pointers
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Element Access - JSON for Modern C++

    Element Access

    There are many ways elements in a JSON value can be accessed:

    • unchecked access via operator[]
    • checked access via at
    • access with default value via value
    • iterators
    • JSON pointers
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/element_access/unchecked_access/index.html b/features/element_access/unchecked_access/index.html index 3f44d9dd5..369af45d5 100644 --- a/features/element_access/unchecked_access/index.html +++ b/features/element_access/unchecked_access/index.html @@ -19,4 +19,4 @@ "age": 42, "hobbies": ["running", "reading", null, "cooking"] } -

    Notes

    Design rationale

    The library behaves differently to std::vector and std::map:

    • std::vector::operator[] never inserts a new element.
    • std::map::operator[] is not available for const values.

    The type json wraps all JSON value types. It would be impossible to remove operator[] for const objects. At the same time, inserting elements for non-const objects is really convenient as it avoids awkward insert calls. To this end, we decided to have an inserting non-const behavior for both arrays and objects.

    Info

    The access is unchecked. In case the passed object key does not exist or the passed array index is invalid, no exception is thrown.

    Danger

    • It is undefined behavior to access a const object with a non-existing key.
    • It is undefined behavior to access a const array with an invalid index.
    • In debug mode, an assertion will fire in both cases. You can disable assertions by defining the preprocessor symbol NDEBUG or redefine the macro JSON_ASSERT(x). See the documentation on runtime assertions for more information.

    Exceptions

    operator[] can only be used with objects (with a string argument) or with arrays (with a numeric argument). For other types, a basic_json::type_error is thrown.

    Summary

    scenario non-const value const value
    access to existing object key reference to existing value is returned const reference to existing value is returned
    access to valid array index reference to existing value is returned const reference to existing value is returned
    access to non-existing object key reference to newly inserted null value is returned undefined behavior; runtime assertion in debug mode
    access to invalid array index reference to newly inserted null value is returned; any index between previous maximal index and passed index are filled with null undefined behavior; runtime assertion in debug mode
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Notes

    Design rationale

    The library behaves differently to std::vector and std::map:

    • std::vector::operator[] never inserts a new element.
    • std::map::operator[] is not available for const values.

    The type json wraps all JSON value types. It would be impossible to remove operator[] for const objects. At the same time, inserting elements for non-const objects is really convenient as it avoids awkward insert calls. To this end, we decided to have an inserting non-const behavior for both arrays and objects.

    Info

    The access is unchecked. In case the passed object key does not exist or the passed array index is invalid, no exception is thrown.

    Danger

    • It is undefined behavior to access a const object with a non-existing key.
    • It is undefined behavior to access a const array with an invalid index.
    • In debug mode, an assertion will fire in both cases. You can disable assertions by defining the preprocessor symbol NDEBUG or redefine the macro JSON_ASSERT(x). See the documentation on runtime assertions for more information.

    Exceptions

    operator[] can only be used with objects (with a string argument) or with arrays (with a numeric argument). For other types, a basic_json::type_error is thrown.

    Summary

    scenario non-const value const value
    access to existing object key reference to existing value is returned const reference to existing value is returned
    access to valid array index reference to existing value is returned const reference to existing value is returned
    access to non-existing object key reference to newly inserted null value is returned undefined behavior; runtime assertion in debug mode
    access to invalid array index reference to newly inserted null value is returned; any index between previous maximal index and passed index are filled with null undefined behavior; runtime assertion in debug mode
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/enum_conversion/index.html b/features/enum_conversion/index.html index e03537191..d3b70e143 100644 --- a/features/enum_conversion/index.html +++ b/features/enum_conversion/index.html @@ -24,4 +24,4 @@ // undefined json value to enum (where the first map entry above is the default) json jPi = 3.14; assert(jPi.get<TaskState>() == TS_INVALID ); -

    Notes

    Just as in Arbitrary Type Conversions above,

    • NLOHMANN_JSON_SERIALIZE_ENUM() MUST be declared in your enum type's namespace (which can be the global namespace), or the library will not be able to locate it, and it will default to integer serialization.
    • It MUST be available (e.g., proper headers must be included) everywhere you use the conversions.

    Other Important points:

    • When using get<ENUM_TYPE>(), undefined JSON values will default to the first pair specified in your map. Select this default pair carefully. If you desire an exception in this circumstance use NLOHMANN_JSON_SERIALIZE_ENUM_STRICT() which behaves identically except for throwing an exception on unrecognized values.
    • If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the map will be returned when converting to or from JSON.
    • To disable the default serialization of enumerators as integers and force a compiler error instead, see JSON_DISABLE_ENUM_SERIALIZATION.
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Notes

    Just as in Arbitrary Type Conversions above,

    • NLOHMANN_JSON_SERIALIZE_ENUM() MUST be declared in your enum type's namespace (which can be the global namespace), or the library will not be able to locate it, and it will default to integer serialization.
    • It MUST be available (e.g., proper headers must be included) everywhere you use the conversions.

    Other Important points:

    • When using get<ENUM_TYPE>(), undefined JSON values will default to the first pair specified in your map. Select this default pair carefully. If you desire an exception in this circumstance use NLOHMANN_JSON_SERIALIZE_ENUM_STRICT() which behaves identically except for throwing an exception on unrecognized values.
    • If an enum or JSON value is specified more than once in your map, the first matching occurrence from the top of the map will be returned when converting to or from JSON.
    • To disable the default serialization of enumerators as integers and force a compiler error instead, see JSON_DISABLE_ENUM_SERIALIZATION.
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/index.html b/features/index.html index 3e26a9c78..9aa9443a6 100644 --- a/features/index.html +++ b/features/index.html @@ -1 +1 @@ - Features - JSON for Modern C++

    Features

    This section describes the features of the library in detail. If you are new to the library, the pages below are roughly ordered along a typical workflow: create or parse a value, access and modify it, convert it to and from your own C++ types, and finally serialize it again.

    Creating and reading values

    Accessing and modifying values

    Converting to and from C++ types

    Serializing values

    How values are stored and configured

    Looking for a specific function?

    This section gives conceptual overviews. For the precise signature, parameters, and return value of a function, see the API Documentation.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Features - JSON for Modern C++

    Features

    This section describes the features of the library in detail. If you are new to the library, the pages below are roughly ordered along a typical workflow: create or parse a value, access and modify it, convert it to and from your own C++ types, and finally serialize it again.

    Creating and reading values

    Accessing and modifying values

    Converting to and from C++ types

    Serializing values

    How values are stored and configured

    Looking for a specific function?

    This section gives conceptual overviews. For the precise signature, parameters, and return value of a function, see the API Documentation.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/iterators/index.html b/features/iterators/index.html index 78f4f38d6..bd472fbbe 100644 --- a/features/iterators/index.html +++ b/features/iterators/index.html @@ -53,4 +53,4 @@ std::cout << *it << std::endl; }

    Output:

    "Hello, world"
-

    Iterator invalidation

    Operations invalidated iterators
    clear all
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Iterator invalidation

    Operations invalidated iterators
    clear all
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/json_patch/index.html b/features/json_patch/index.html index 350521d89..db04f4ae9 100644 --- a/features/json_patch/index.html +++ b/features/json_patch/index.html @@ -105,4 +105,4 @@ "world" ] } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/json_pointer/index.html b/features/json_pointer/index.html index 191c6e138..d40eb640a 100644 --- a/features/json_pointer/index.html +++ b/features/json_pointer/index.html @@ -45,4 +45,4 @@ "/nested/three/1": false }

    The reverse function, unflatten recreates the original value.

    auto j_original = j_flat.unflatten();
-

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/macros/index.html b/features/macros/index.html index 436c7541b..49ccc9cbf 100644 --- a/features/macros/index.html +++ b/features/macros/index.html @@ -1 +1 @@ - Supported Macros - JSON for Modern C++

    Supported Macros

    Some aspects of the library can be configured by defining preprocessor macros before including the json.hpp header. See also the API documentation for macros for examples and more information.

    JSON_ASSERT(x)

    This macro controls which code is executed for runtime assertions of the library.

    See full documentation of JSON_ASSERT(x).

    JSON_BRACE_INIT_COPY_SEMANTICS

    When defined to 1, single-element brace initialization of a basic_json value (e.g., json j{value};) is treated as a copy/move of the element rather than wrapping it in a single-element array. The default value is 0, which preserves the existing behavior.

    See full documentation of JSON_BRACE_INIT_COPY_SEMANTICS.

    JSON_CATCH_USER(exception)

    This macro overrides catch calls inside the library.

    See full documentation of JSON_CATCH_USER(exception).

    JSON_DIAGNOSTICS

    This macro enables extended diagnostics for exception messages. Possible values are 1 to enable or 0 to disable (default).

    When enabled, exception messages contain a JSON Pointer to the JSON value that triggered the exception, see Extended diagnostic messages for an example. Note that enabling this macro increases the size of every JSON value by one pointer and adds some runtime overhead.

    The diagnostics messages can also be controlled with the CMake option JSON_Diagnostics (OFF by default) which sets JSON_DIAGNOSTICS accordingly.

    See full documentation of JSON_DIAGNOSTICS.

    JSON_DIAGNOSTIC_POSITIONS

    When enabled, two new member functions start_pos() and end_pos() are added to basic_json values. If the value was created by calling theparse function, then these functions allow querying the byte positions of the value in the input it was parsed from. The byte positions are also used in exceptions to help locate errors.

    The diagnostics positions can also be controlled with the CMake option JSON_Diagnostic_Positions (OFF by default) which sets JSON_DIAGNOSTIC_POSITIONS accordingly.

    See full documentation of JSON_DIAGNOSTIC_POSITIONS

    JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, JSON_HAS_CPP_26

    The library targets C++11, but also supports some features introduced in later C++ versions (e.g., std::string_view support for C++17). For these new features, the library implements some preprocessor checks to determine the C++ standard. By defining any of these symbols, the internal check is overridden and the provided C++ version is unconditionally assumed. This can be helpful for compilers that only implement parts of the standard and would be detected incorrectly.

    See full documentation of JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, and JSON_HAS_CPP_26.

    JSON_HAS_FILESYSTEM, JSON_HAS_EXPERIMENTAL_FILESYSTEM

    When compiling with C++17, the library provides conversions from and to std::filesystem::path. As compiler support for filesystem is limited, the library tries to detect whether <filesystem>/std::filesystem (JSON_HAS_FILESYSTEM) or <experimental/filesystem>/std::experimental::filesystem (JSON_HAS_EXPERIMENTAL_FILESYSTEM) should be used. To override the built-in check, define JSON_HAS_FILESYSTEM or JSON_HAS_EXPERIMENTAL_FILESYSTEM to 1.

    See full documentation of JSON_HAS_FILESYSTEM and JSON_HAS_EXPERIMENTAL_FILESYSTEM.

    JSON_NOEXCEPTION

    Exceptions can be switched off by defining the symbol JSON_NOEXCEPTION.

    See full documentation of JSON_NOEXCEPTION.

    JSON_DISABLE_ENUM_SERIALIZATION

    When defined, default parse and serialize functions for enums are excluded and have to be provided by the user, for example, using NLOHMANN_JSON_SERIALIZE_ENUM.

    See full documentation of JSON_DISABLE_ENUM_SERIALIZATION.

    JSON_NO_IO

    When defined, headers <cstdio>, <ios>, <iosfwd>, <istream>, and <ostream> are not included and parse functions relying on these headers are excluded. This is relevant for environment where these I/O functions are disallowed for security reasons (e.g., Intel Software Guard Extensions (SGX)).

    See full documentation of JSON_NO_IO.

    JSON_SKIP_LIBRARY_VERSION_CHECK

    When defined, the library will not create a compiler warning when a different version of the library was already included.

    See full documentation of JSON_SKIP_LIBRARY_VERSION_CHECK.

    JSON_SKIP_UNSUPPORTED_COMPILER_CHECK

    When defined, the library will not create a compile error when a known unsupported compiler is detected. This allows using the library with compilers that do not fully support C++11 and may only work if unsupported features are not used.

    See full documentation of JSON_SKIP_UNSUPPORTED_COMPILER_CHECK.

    JSON_THROW_USER(exception)

    This macro overrides throw calls inside the library. The argument is the exception to be thrown.

    See full documentation of JSON_THROW_USER(exception).

    JSON_TRY_USER

    This macro overrides try calls inside the library.

    See full documentation of JSON_TRY_USER.

    JSON_USE_IMPLICIT_CONVERSIONS

    When defined to 0, implicit conversions are switched off. By default, implicit conversions are switched on.

    See full documentation of JSON_USE_IMPLICIT_CONVERSIONS.

    JSON_USE_GLOBAL_UDLS

    When defined to 1 (default), the user-defined string literals operator""_json and operator""_json_pointer are placed into the global namespace instead of nlohmann::literals::json_literals.

    See full documentation of JSON_USE_GLOBAL_UDLS.

    JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON

    When defined to 1, the library restores the legacy behavior in which a discarded value compared equal to itself. This behavior is deprecated and switched off (0) by default.

    See full documentation of JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON.

    NLOHMANN_DEFINE_TYPE_*(...), NLOHMANN_DEFINE_DERIVED_TYPE_*(...)

    The library defines 12 macros to simplify the serialization/deserialization of types. See the page on arbitrary type conversion for a detailed discussion.

    NLOHMANN_JSON_NAMESPACE, NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END, NLOHMANN_JSON_NAMESPACE_NO_VERSION

    These macros relate to the versioned, inline nlohmann namespace:

    • NLOHMANN_JSON_NAMESPACE evaluates to the full name of the nlohmann namespace (including the inline ABI namespace).
    • NLOHMANN_JSON_NAMESPACE_BEGIN / NLOHMANN_JSON_NAMESPACE_END open and close the namespace (for example, to add specializations).
    • NLOHMANN_JSON_NAMESPACE_NO_VERSION, when defined to 1, omits the version component from the inline namespace.

    See the nlohmann Namespace page, and the full documentation of NLOHMANN_JSON_NAMESPACE, NLOHMANN_JSON_NAMESPACE_BEGIN / NLOHMANN_JSON_NAMESPACE_END, and NLOHMANN_JSON_NAMESPACE_NO_VERSION.

    NLOHMANN_JSON_SERIALIZE_ENUM(type, ...)

    This macro simplifies the serialization/deserialization of enum types. See Specializing enum conversion for more information.

    See full documentation of NLOHMANN_JSON_SERIALIZE_ENUM.

    A strict variant NLOHMANN_JSON_SERIALIZE_ENUM_STRICT throws an exception on undefined input instead of falling back to the first mapping.

    NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, NLOHMANN_JSON_VERSION_PATCH

    These macros are defined by the library and contain the version numbers according to Semantic Versioning 2.0.0.

    See full documentation of NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, and NLOHMANN_JSON_VERSION_PATCH.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Supported Macros - JSON for Modern C++

    Supported Macros

    Some aspects of the library can be configured by defining preprocessor macros before including the json.hpp header. See also the API documentation for macros for examples and more information.

    JSON_ASSERT(x)

    This macro controls which code is executed for runtime assertions of the library.

    See full documentation of JSON_ASSERT(x).

    JSON_BRACE_INIT_COPY_SEMANTICS

    When defined to 1, single-element brace initialization of a basic_json value (e.g., json j{value};) is treated as a copy/move of the element rather than wrapping it in a single-element array. The default value is 0, which preserves the existing behavior.

    See full documentation of JSON_BRACE_INIT_COPY_SEMANTICS.

    JSON_CATCH_USER(exception)

    This macro overrides catch calls inside the library.

    See full documentation of JSON_CATCH_USER(exception).

    JSON_DIAGNOSTICS

    This macro enables extended diagnostics for exception messages. Possible values are 1 to enable or 0 to disable (default).

    When enabled, exception messages contain a JSON Pointer to the JSON value that triggered the exception, see Extended diagnostic messages for an example. Note that enabling this macro increases the size of every JSON value by one pointer and adds some runtime overhead.

    The diagnostics messages can also be controlled with the CMake option JSON_Diagnostics (OFF by default) which sets JSON_DIAGNOSTICS accordingly.

    See full documentation of JSON_DIAGNOSTICS.

    JSON_DIAGNOSTIC_POSITIONS

    When enabled, two new member functions start_pos() and end_pos() are added to basic_json values. If the value was created by calling theparse function, then these functions allow querying the byte positions of the value in the input it was parsed from. The byte positions are also used in exceptions to help locate errors.

    The diagnostics positions can also be controlled with the CMake option JSON_Diagnostic_Positions (OFF by default) which sets JSON_DIAGNOSTIC_POSITIONS accordingly.

    See full documentation of JSON_DIAGNOSTIC_POSITIONS

    JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, JSON_HAS_CPP_26

    The library targets C++11, but also supports some features introduced in later C++ versions (e.g., std::string_view support for C++17). For these new features, the library implements some preprocessor checks to determine the C++ standard. By defining any of these symbols, the internal check is overridden and the provided C++ version is unconditionally assumed. This can be helpful for compilers that only implement parts of the standard and would be detected incorrectly.

    See full documentation of JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, and JSON_HAS_CPP_26.

    JSON_HAS_FILESYSTEM, JSON_HAS_EXPERIMENTAL_FILESYSTEM

    When compiling with C++17, the library provides conversions from and to std::filesystem::path. As compiler support for filesystem is limited, the library tries to detect whether <filesystem>/std::filesystem (JSON_HAS_FILESYSTEM) or <experimental/filesystem>/std::experimental::filesystem (JSON_HAS_EXPERIMENTAL_FILESYSTEM) should be used. To override the built-in check, define JSON_HAS_FILESYSTEM or JSON_HAS_EXPERIMENTAL_FILESYSTEM to 1.

    See full documentation of JSON_HAS_FILESYSTEM and JSON_HAS_EXPERIMENTAL_FILESYSTEM.

    JSON_NOEXCEPTION

    Exceptions can be switched off by defining the symbol JSON_NOEXCEPTION.

    See full documentation of JSON_NOEXCEPTION.

    JSON_DISABLE_ENUM_SERIALIZATION

    When defined, default parse and serialize functions for enums are excluded and have to be provided by the user, for example, using NLOHMANN_JSON_SERIALIZE_ENUM.

    See full documentation of JSON_DISABLE_ENUM_SERIALIZATION.

    JSON_NO_IO

    When defined, headers <cstdio>, <ios>, <iosfwd>, <istream>, and <ostream> are not included and parse functions relying on these headers are excluded. This is relevant for environment where these I/O functions are disallowed for security reasons (e.g., Intel Software Guard Extensions (SGX)).

    See full documentation of JSON_NO_IO.

    JSON_SKIP_LIBRARY_VERSION_CHECK

    When defined, the library will not create a compiler warning when a different version of the library was already included.

    See full documentation of JSON_SKIP_LIBRARY_VERSION_CHECK.

    JSON_SKIP_UNSUPPORTED_COMPILER_CHECK

    When defined, the library will not create a compile error when a known unsupported compiler is detected. This allows using the library with compilers that do not fully support C++11 and may only work if unsupported features are not used.

    See full documentation of JSON_SKIP_UNSUPPORTED_COMPILER_CHECK.

    JSON_THROW_USER(exception)

    This macro overrides throw calls inside the library. The argument is the exception to be thrown.

    See full documentation of JSON_THROW_USER(exception).

    JSON_TRY_USER

    This macro overrides try calls inside the library.

    See full documentation of JSON_TRY_USER.

    JSON_USE_IMPLICIT_CONVERSIONS

    When defined to 0, implicit conversions are switched off. By default, implicit conversions are switched on.

    See full documentation of JSON_USE_IMPLICIT_CONVERSIONS.

    JSON_USE_GLOBAL_UDLS

    When defined to 1 (default), the user-defined string literals operator""_json and operator""_json_pointer are placed into the global namespace instead of nlohmann::literals::json_literals.

    See full documentation of JSON_USE_GLOBAL_UDLS.

    JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON

    When defined to 1, the library restores the legacy behavior in which a discarded value compared equal to itself. This behavior is deprecated and switched off (0) by default.

    See full documentation of JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON.

    NLOHMANN_DEFINE_TYPE_*(...), NLOHMANN_DEFINE_DERIVED_TYPE_*(...)

    The library defines 12 macros to simplify the serialization/deserialization of types. See the page on arbitrary type conversion for a detailed discussion.

    NLOHMANN_JSON_NAMESPACE, NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END, NLOHMANN_JSON_NAMESPACE_NO_VERSION

    These macros relate to the versioned, inline nlohmann namespace:

    • NLOHMANN_JSON_NAMESPACE evaluates to the full name of the nlohmann namespace (including the inline ABI namespace).
    • NLOHMANN_JSON_NAMESPACE_BEGIN / NLOHMANN_JSON_NAMESPACE_END open and close the namespace (for example, to add specializations).
    • NLOHMANN_JSON_NAMESPACE_NO_VERSION, when defined to 1, omits the version component from the inline namespace.

    See the nlohmann Namespace page, and the full documentation of NLOHMANN_JSON_NAMESPACE, NLOHMANN_JSON_NAMESPACE_BEGIN / NLOHMANN_JSON_NAMESPACE_END, and NLOHMANN_JSON_NAMESPACE_NO_VERSION.

    NLOHMANN_JSON_SERIALIZE_ENUM(type, ...)

    This macro simplifies the serialization/deserialization of enum types. See Specializing enum conversion for more information.

    See full documentation of NLOHMANN_JSON_SERIALIZE_ENUM.

    A strict variant NLOHMANN_JSON_SERIALIZE_ENUM_STRICT throws an exception on undefined input instead of falling back to the first mapping.

    NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, NLOHMANN_JSON_VERSION_PATCH

    These macros are defined by the library and contain the version numbers according to Semantic Versioning 2.0.0.

    See full documentation of NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, and NLOHMANN_JSON_VERSION_PATCH.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/merge_patch/index.html b/features/merge_patch/index.html index 98063a96b..5924d2e18 100644 --- a/features/merge_patch/index.html +++ b/features/merge_patch/index.html @@ -50,4 +50,4 @@ ], "title": "Hello!" } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/modifying_values/index.html b/features/modifying_values/index.html index ef11a5615..26bfda076 100644 --- a/features/modifying_values/index.html +++ b/features/modifying_values/index.html @@ -54,4 +54,4 @@ json a = {1, 2, 3, 4}; a.erase(1); // [1,3,4] (erase by index) -

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/modules/index.html b/features/modules/index.html index 67ee26894..9b49b6779 100644 --- a/features/modules/index.html +++ b/features/modules/index.html @@ -7,4 +7,4 @@ std::ifstream f("example.json"); json data = json::parse(f); -

    Modules do not export macros

    It should be noted that as modules do not export macros, the nlohmann.json module will not export any macros.

    Exported symbols

    Only the following symbols are exported from nlohmann.json:

    • nlohmann::adl_serializer
    • nlohmann::basic_json
    • nlohmann::json
    • nlohmann::json_pointer
    • nlohmann::ordered_json
    • nlohmann::ordered_map
    • nlohmann::to_string
    • nlohmann::literals::json_literals::operator""_json
    • nlohmann::literals::json_literals::operator""_json_pointer

    Additionally, the following nlohmann::detail symbols are exported, solely to work around an MSVC compilation issue (#3970). They are implementation details, not part of the public API, and should not be used directly:

    • nlohmann::detail::json_sax_dom_callback_parser
    • nlohmann::detail::unknown_size

    Known issues

    C++20 modules support is exercised in CI against current GCC and Clang on Ubuntu, and the default MSVC toolset on Windows Server 2022 — there is no documented minimum compiler version, unlike feature-test-macro-gated features such as JSON_HAS_RANGES.

    Known compiler issues

    • GCC may emit "redefinition" errors when #include <nlohmann/json.hpp> appears in a module preamble together with other imports. This is an upstream GCC bug, not yet resolved as of GCC 16. Workarounds: include nlohmann/json.hpp before other #includes, use import nlohmann.json; instead, or upgrade GCC. (issue #5103)
    • MSVC could fail with C2039: 'json_sax_dom_callback_parser' is not a member of ... detail; fixed by exporting the required internal symbols from json.cppm (see Exported symbols above). (issue #3970)

    If you hit a different module-related build failure, search existing issues before filing a new one.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Modules do not export macros

    It should be noted that as modules do not export macros, the nlohmann.json module will not export any macros.

    Exported symbols

    Only the following symbols are exported from nlohmann.json:

    • nlohmann::adl_serializer
    • nlohmann::basic_json
    • nlohmann::json
    • nlohmann::json_pointer
    • nlohmann::ordered_json
    • nlohmann::ordered_map
    • nlohmann::to_string
    • nlohmann::literals::json_literals::operator""_json
    • nlohmann::literals::json_literals::operator""_json_pointer

    Additionally, the following nlohmann::detail symbols are exported, solely to work around an MSVC compilation issue (#3970). They are implementation details, not part of the public API, and should not be used directly:

    • nlohmann::detail::json_sax_dom_callback_parser
    • nlohmann::detail::unknown_size

    Known issues

    C++20 modules support is exercised in CI against current GCC and Clang on Ubuntu, and the default MSVC toolset on Windows Server 2022 — there is no documented minimum compiler version, unlike feature-test-macro-gated features such as JSON_HAS_RANGES.

    Known compiler issues

    • GCC may emit "redefinition" errors when #include <nlohmann/json.hpp> appears in a module preamble together with other imports. This is an upstream GCC bug, not yet resolved as of GCC 16. Workarounds: include nlohmann/json.hpp before other #includes, use import nlohmann.json; instead, or upgrade GCC. (issue #5103)
    • MSVC could fail with C2039: 'json_sax_dom_callback_parser' is not a member of ... detail; fixed by exporting the required internal symbols from json.cppm (see Exported symbols above). (issue #3970)

    If you hit a different module-related build failure, search existing issues before filing a new one.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/namespace/index.html b/features/namespace/index.html index 81a170eb3..34918310f 100644 --- a/features/namespace/index.html +++ b/features/namespace/index.html @@ -9,4 +9,4 @@ app --> json_diag app --> library

    In releases prior to 3.11.0, mixing any version of the JSON library with different JSON_DIAGNOSTICS settings would result in a crashing application. If some_library never passes instances of JSON library types to the application, this scenario became safe in version 3.11.0 and above due to the inline namespace yielding distinct symbol names.

    Limitations

    Neither the compiler nor the linker will issue as much as a warning when translation units – intended to be linked together and that include different versions and/or configurations of the JSON library – exchange and use library types.

    There is an exception when forward declarations are used (i.e., when including json_fwd.hpp) in which case the linker may complain about undefined references.

    Disabling the version component

    Different versions are not necessarily ABI-incompatible, but the project does not actively track changes in the ABI and recommends that all parts of a codebase exchanging library types be built with the same version. Users can, at their own risk, disable the version component of the inline namespace, allowing different versions – but not configurations – to be used in cases where the linker would otherwise output undefined reference errors.

    To do so, define NLOHMANN_JSON_NAMESPACE_NO_VERSION to 1.

    This applies to version 3.11.2 and above only; versions 3.11.0 and 3.11.1 can apply the technique described in the next section to emulate the effect of the NLOHMANN_JSON_NAMESPACE_NO_VERSION macro.

    Use at your own risk

    Disabling the namespace version component and mixing ABI-incompatible versions will result in crashes or incorrect behavior. You have been warned!

    Disabling the inline namespace completely

    When interoperability with code using a pre-3.11.0 version of the library is required, users can, at their own risk restore the old namespace layout by redefining NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END as follows:

    #define NLOHMANN_JSON_NAMESPACE_BEGIN  namespace nlohmann {
 #define NLOHMANN_JSON_NAMESPACE_END    }
-

    Use at your own risk

    Overriding the namespace and mixing ABI-incompatible versions will result in crashes or incorrect behavior. You have been warned!

    Version history

    • Introduced inline namespace (json_v3_11_0[_abi-tag]*) in version 3.11.0.
    • Changed structure of inline namespace in version 3.11.2.
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Use at your own risk

    Overriding the namespace and mixing ABI-incompatible versions will result in crashes or incorrect behavior. You have been warned!

    Version history

    • Introduced inline namespace (json_v3_11_0[_abi-tag]*) in version 3.11.0.
    • Changed structure of inline namespace in version 3.11.2.
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/object_order/index.html b/features/object_order/index.html index 37fe9d891..50064d8d7 100644 --- a/features/object_order/index.html +++ b/features/object_order/index.html @@ -57,4 +57,4 @@ "three": 3, "two": 2 } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/parsing/index.html b/features/parsing/index.html index 67eeda1bd..7fd0ff0ff 100644 --- a/features/parsing/index.html +++ b/features/parsing/index.html @@ -4,4 +4,4 @@ // parse from a file std::ifstream f("example.json"); json data = json::parse(f); -

    The input must be encoded in UTF-8; other encodings are not supported. A single input may contain only one JSON value. Inputs consisting of multiple values separated by newlines are handled by the JSON Lines format.

    By default, the library rejects comments and trailing commas. Both can be enabled with parameters of the parse function — see comments and trailing commas.

    SAX vs. DOM parsing

    The library offers two parsing models:

    • DOM parsing (the default): the complete input is read and stored as an in-memory basic_json value that can be traversed and modified freely. This is what parse does, and it is the right choice for most use cases.
    • SAX parsing: instead of building a value, the parser reports events (such as "a string was read" or "an object started") to a handler that you implement. This avoids building the full value in memory and is useful for very large inputs or when you only need to extract parts of the input. See the SAX interface for details and sax_parse for the API.

    You can influence a DOM parse without switching to the SAX interface by passing a parser callback, which is called during parsing and can, for example, discard parts of the input.

    Exceptions

    When the input is not valid JSON, the parse function throws an exception by default. If exceptions are undesired or unavailable, the parser can instead return a discarded value, or accept can be used to only check whether an input is valid JSON. See parsing and exceptions for the available options.

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    The input must be encoded in UTF-8; other encodings are not supported. A single input may contain only one JSON value. Inputs consisting of multiple values separated by newlines are handled by the JSON Lines format.

    By default, the library rejects comments and trailing commas. Both can be enabled with parameters of the parse function — see comments and trailing commas.

    SAX vs. DOM parsing

    The library offers two parsing models:

    • DOM parsing (the default): the complete input is read and stored as an in-memory basic_json value that can be traversed and modified freely. This is what parse does, and it is the right choice for most use cases.
    • SAX parsing: instead of building a value, the parser reports events (such as "a string was read" or "an object started") to a handler that you implement. This avoids building the full value in memory and is useful for very large inputs or when you only need to extract parts of the input. See the SAX interface for details and sax_parse for the API.

    You can influence a DOM parse without switching to the SAX interface by passing a parser callback, which is called during parsing and can, for example, discard parts of the input.

    Exceptions

    When the input is not valid JSON, the parse function throws an exception by default. If exceptions are undesired or unavailable, the parser can instead return a discarded value, or accept can be used to only check whether an input is valid JSON. See parsing and exceptions for the available options.

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/parsing/json_lines/index.html b/features/parsing/json_lines/index.html index 16fdfed98..aa56d4dae 100644 --- a/features/parsing/json_lines/index.html +++ b/features/parsing/json_lines/index.html @@ -33,4 +33,4 @@ { std::cout << j << std::endl; } -

    with a JSON Lines input does not work, because the parser will try to parse one value after the last one.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    with a JSON Lines input does not work, because the parser will try to parse one value after the last one.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/parsing/parse_exceptions/index.html b/features/parsing/parse_exceptions/index.html index 8465a7378..554e7c4ca 100644 --- a/features/parsing/parse_exceptions/index.html +++ b/features/parsing/parse_exceptions/index.html @@ -63,4 +63,4 @@ last read: "3,]" parsing unsuccessful! parsed value: [1,2,3] -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/parsing/parser_callbacks/index.html b/features/parsing/parser_callbacks/index.html index 806736e69..4de3afb73 100644 --- a/features/parsing/parser_callbacks/index.html +++ b/features/parsing/parser_callbacks/index.html @@ -90,4 +90,4 @@ "Width": 800 } } -
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/parsing/sax_interface/index.html b/features/parsing/sax_interface/index.html index cd3bf4335..94bbd2488 100644 --- a/features/parsing/sax_interface/index.html +++ b/features/parsing/sax_interface/index.html @@ -49,4 +49,4 @@ class sax_t ["json::sax_t"] { // called when a parse error occurs; byte position, the last token, and an exception is passed bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex); -

    The return value of each function determines whether parsing should proceed.

    To implement your own SAX handler, proceed as follows:

    1. Implement the SAX interface in a class. You can use class nlohmann::json_sax<json> as base class, but you can also use any class where the functions described above are implemented and public.
    2. Create an object of your SAX interface class, e.g. my_sax.
    3. Call bool json::sax_parse(input, &my_sax); where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.

    Note the sax_parse function only returns a bool indicating the result of the last executed SAX event. It does not return json value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your parse_error implementation. Internally, the SAX interface is used for the DOM parser (class json_sax_dom_parser) as well as the acceptor (json_sax_acceptor), see file json_sax.hpp.

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    The return value of each function determines whether parsing should proceed.

    To implement your own SAX handler, proceed as follows:

    1. Implement the SAX interface in a class. You can use class nlohmann::json_sax<json> as base class, but you can also use any class where the functions described above are implemented and public.
    2. Create an object of your SAX interface class, e.g. my_sax.
    3. Call bool json::sax_parse(input, &my_sax); where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.

    Note the sax_parse function only returns a bool indicating the result of the last executed SAX event. It does not return json value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your parse_error implementation. Internally, the SAX interface is used for the DOM parser (class json_sax_dom_parser) as well as the acceptor (json_sax_acceptor), see file json_sax.hpp.

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/serialization/index.html b/features/serialization/index.html index 3e3a37e37..d12259bf2 100644 --- a/features/serialization/index.html +++ b/features/serialization/index.html @@ -138,4 +138,4 @@

    Avoiding invalid UTF-8

    The best fix is to ensure that all strings are UTF-8 encoded before storing them. See the FAQ on non-ASCII characters for how to convert wide or Latin-1 strings.

    Numbers, NaN, and binary values

    • Numbers are serialized with enough precision to round-trip; see number serialization.
    • NaN and infinity cannot be represented in JSON and are serialized as null; see NaN handling. The binary formats can preserve them.
    • Binary values have no JSON representation and are serialized as a helper object for debugging only; see binary values.

    Using std::format, std::print, and fmt

    Since version 3.12.0, JSON values can be formatted directly with C++20's std::format whenever the standard library provides the <format> header (controlled by JSON_HAS_STD_FORMAT). This is enabled by the std::formatter<basic_json> specialization, which also makes JSON values work with std::format_to and with C++23's std::print/std::println:

    std::print("{}", j);      // compact, like j.dump()
 std::print("{:2}", j);    // pretty-printed with indent 2 (like j.dump(2))
 std::println("{:#}", j);  // pretty-printed with the default indent
-

    The format spec mirrors the dump parameters: "{:#}" pretty-prints, a width such as "{:2}" sets the indent, and a fill-and-align prefix such as "{:.>#}" sets the indent character.

    For the {fmt} library, the library ships a format_as helper. Note its behavior depends on the fmt version; see the FAQ entry for the details and a recipe for a full fmt::formatter specialization.

    Serializing to other formats

    Besides JSON text, a value can also be serialized to the more compact binary formats (BJData, BSON, CBOR, MessagePack, UBJSON).

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    The format spec mirrors the dump parameters: "{:#}" pretty-prints, a width such as "{:2}" sets the indent, and a fill-and-align prefix such as "{:.>#}" sets the indent character.

    For the {fmt} library, the library ships a format_as helper. Note its behavior depends on the fmt version; see the FAQ entry for the details and a recipe for a full fmt::formatter specialization.

    Serializing to other formats

    Besides JSON text, a value can also be serialized to the more compact binary formats (BJData, BSON, CBOR, MessagePack, UBJSON).

    See also

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/trailing_commas/index.html b/features/trailing_commas/index.html index ebe59ebd5..34ea4a100 100644 --- a/features/trailing_commas/index.html +++ b/features/trailing_commas/index.html @@ -58,4 +58,4 @@ "Neptune" ] } -
    Copyright © 2013-2026 Niels Lohmann
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    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/types/index.html b/features/types/index.html index c163140de..b84e32b8c 100644 --- a/features/types/index.html +++ b/features/types/index.html @@ -77,4 +77,4 @@ basic_json .. value_t

    Template arguments< basic_json, // value_type std::allocator<basic_json> // allocator_type > -

    Limits

    RFC 8259 specifies:

    An implementation may set limits on the maximum depth of nesting.

    In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON array.

    Storage

    Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of type array_t* must be dereferenced.

    Strings

    RFC 8259 describes JSON strings as follows:

    A string is a sequence of zero or more Unicode characters.

    Unicode values are split by the JSON class into byte-sized characters during deserialization.

    Default type

    With the default values for StringType (std::string), the default value for string_t is std::string.

    Encoding

    Strings are stored in UTF-8 encoding. Therefore, functions like std::string::size() or std::string::length() return the number of bytes in the string rather than the number of characters or glyphs.

    String comparison

    RFC 8259 states:

    Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that "a\\b" and "a\u005Cb" are not equal.

    This implementation is interoperable as it does compare strings code unit by code unit.

    Storage

    String values are stored as pointers in a basic_json type. That is, for any access to string values, a pointer of type string_t* must be dereferenced.

    Booleans

    RFC 8259 implicitly describes a boolean as a type which differentiates the two literals true and false.

    Default type

    With the default values for BooleanType (bool), the default value for boolean_t is bool.

    Storage

    Boolean values are stored directly inside a basic_json type.

    Numbers

    See the number handling article for a detailed discussion on how numbers are handled by this library.

    RFC 8259 describes numbers as follows:

    The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.

    This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer, or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t, and number_float_t are used.

    Default types

    With the default values for NumberIntegerType (std::int64_t), the default value for number_integer_t is std::int64_t. With the default values for NumberUnsignedType (std::uint64_t), the default value for number_unsigned_t is std::uint64_t. With the default values for NumberFloatType (double), the default value for number_float_t is double.

    Default behavior

    • The restrictions about leading zeros are not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as an octal number. Internally, the value will be stored as a decimal number. For instance, the C++ integer literal 010 will be serialized to 8. During deserialization, leading zeros yield an error.
    • Not-a-number (NaN) values will be serialized to null.

    Limits

    RFC 8259 specifies:

    An implementation may set limits on the range and precision of numbers.

    When the default type is used, the maximal integer number that can be stored is 9223372036854775807 (INT64_MAX) and the minimal integer number that can be stored is -9223372036854775808 (INT64_MIN). Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will automatically be stored as number_unsigned_t or number_float_t.

    When the default type is used, the maximal unsigned integer number that can be stored is 18446744073709551615 (UINT64_MAX) and the minimal integer number that can be stored is 0. Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will automatically be stored as number_integer_t or number_float_t.

    RFC 8259 further states:

    Note that when such software is used, numbers that are integers and are in the range [-2^{53}+1, 2^{53}-1] are interoperable in the sense that implementations will agree exactly on their numeric values.

    As this range is a subrange of the exactly supported range [INT64_MIN, INT64_MAX], this class's integer type is interoperable.

    RFC 8259 states:

    This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.

    This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note values smaller than -1.79769313486232e+308 and values greater than 1.79769313486232e+308 will be stored as NaN internally and be serialized to null.

    Storage

    Integer number values, unsigned integer number values, and floating-point number values are stored directly inside a basic_json type.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Limits

    RFC 8259 specifies:

    An implementation may set limits on the maximum depth of nesting.

    In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON array.

    Storage

    Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of type array_t* must be dereferenced.

    Strings

    RFC 8259 describes JSON strings as follows:

    A string is a sequence of zero or more Unicode characters.

    Unicode values are split by the JSON class into byte-sized characters during deserialization.

    Default type

    With the default values for StringType (std::string), the default value for string_t is std::string.

    Encoding

    Strings are stored in UTF-8 encoding. Therefore, functions like std::string::size() or std::string::length() return the number of bytes in the string rather than the number of characters or glyphs.

    String comparison

    RFC 8259 states:

    Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that "a\\b" and "a\u005Cb" are not equal.

    This implementation is interoperable as it does compare strings code unit by code unit.

    Storage

    String values are stored as pointers in a basic_json type. That is, for any access to string values, a pointer of type string_t* must be dereferenced.

    Booleans

    RFC 8259 implicitly describes a boolean as a type which differentiates the two literals true and false.

    Default type

    With the default values for BooleanType (bool), the default value for boolean_t is bool.

    Storage

    Boolean values are stored directly inside a basic_json type.

    Numbers

    See the number handling article for a detailed discussion on how numbers are handled by this library.

    RFC 8259 describes numbers as follows:

    The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.

    This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer, or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t, and number_float_t are used.

    Default types

    With the default values for NumberIntegerType (std::int64_t), the default value for number_integer_t is std::int64_t. With the default values for NumberUnsignedType (std::uint64_t), the default value for number_unsigned_t is std::uint64_t. With the default values for NumberFloatType (double), the default value for number_float_t is double.

    Default behavior

    • The restrictions about leading zeros are not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as an octal number. Internally, the value will be stored as a decimal number. For instance, the C++ integer literal 010 will be serialized to 8. During deserialization, leading zeros yield an error.
    • Not-a-number (NaN) values will be serialized to null.

    Limits

    RFC 8259 specifies:

    An implementation may set limits on the range and precision of numbers.

    When the default type is used, the maximal integer number that can be stored is 9223372036854775807 (INT64_MAX) and the minimal integer number that can be stored is -9223372036854775808 (INT64_MIN). Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will automatically be stored as number_unsigned_t or number_float_t.

    When the default type is used, the maximal unsigned integer number that can be stored is 18446744073709551615 (UINT64_MAX) and the minimal integer number that can be stored is 0. Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will automatically be stored as number_integer_t or number_float_t.

    RFC 8259 further states:

    Note that when such software is used, numbers that are integers and are in the range [-2^{53}+1, 2^{53}-1] are interoperable in the sense that implementations will agree exactly on their numeric values.

    As this range is a subrange of the exactly supported range [INT64_MIN, INT64_MAX], this class's integer type is interoperable.

    RFC 8259 states:

    This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.

    This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note values smaller than -1.79769313486232e+308 and values greater than 1.79769313486232e+308 will be stored as NaN internally and be serialized to null.

    Storage

    Integer number values, unsigned integer number values, and floating-point number values are stored directly inside a basic_json type.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/features/types/number_handling/index.html b/features/types/number_handling/index.html index b0446191e..9331cf230 100644 --- a/features/types/number_handling/index.html +++ b/features/types/number_handling/index.html @@ -54,4 +54,4 @@ val=nan }

    Note this approach also has the advantage that it can react on non-numerical JSON value types such as strings.

    (Example taken from #777.)

    Determine number types

    As the example in Number conversion shows, there are different functions to determine the type of the stored number:

    function unsigned integer signed integer floating-point string
    is_number() true true true false
    is_number_integer() true true false false
    is_number_unsigned() true false false false
    is_number_float() false false true false
    type_name() "number" "number" "number" "string"
    type() number_unsigned number_integer number_float string

    Template number types

    The number types can be changed with template parameters.

    position number type default type possible values
    5 signed integers std::int64_t std::int32_t, std::int16_t, etc.
    6 unsigned integers std::uint64_t std::uint32_t, std::uint16_t, etc.
    7 floating-point double float, long double

    Constraints on number types

    • The type for signed integers must be convertible from long long. The type for floating-point numbers is used in case of overflow.
    • The type for unsigned integers must be convertible from unsigned long long. The type for floating-point numbers is used in case of overflow.
    • The types for signed and unsigned integers must be distinct, see #2573.
    • Only double, float, and long double are supported for floating-point numbers.

    Example

    A basic_json type that uses long double as floating-point type.

    using json_ld = nlohmann::basic_json<std::map, std::vector, std::string, bool,
                                      std::int64_t, std::uint64_t, long double>;
-

    Note values should then be parsed with json_ld::parse rather than json::parse as the latter would parse floating-point values to double before then converting them to long double.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +

    Note values should then be parsed with json_ld::parse rather than json::parse as the latter would parse floating-point values to double before then converting them to long double.

    \ No newline at end of file diff --git a/home/architecture/index.html b/home/architecture/index.html index 8deeb6db4..fe7d624a4 100644 --- a/home/architecture/index.html +++ b/home/architecture/index.html @@ -52,4 +52,4 @@ template<class T> void from_json(const basic_json& j, T& t); -

    Additional features

    Details namespace

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    Additional features

    Details namespace

    \ No newline at end of file diff --git a/home/customers/index.html b/home/customers/index.html index 320bc788f..5d005c2c7 100644 --- a/home/customers/index.html +++ b/home/customers/index.html @@ -1 +1 @@ - Customers - JSON for Modern C++
    Skip to content

    Customers

    The library is used in multiple projects, applications, operating systems, etc. The list below is not exhaustive, but the result of an internet search. If you know further customers of the library, please let me know.

    Space Exploration

    • Peregrine Lunar Lander Flight 01 - The library was used for payload management in the Peregrine Moon Lander, developed by Astrobotic Technology and launched as part of NASA's Commercial Lunar Payload Services (CLPS) program. After six days in orbit, the spacecraft was intentionally redirected into Earth's atmosphere, where it burned up over the Pacific Ocean on January 18, 2024.

    Automotive

    Gaming and Entertainment

    • Assassin's Creed: Mirage, a stealth-action game set in the Middle East, focusing on the journey of a young assassin with classic parkour and stealth mechanics
    • Chasm: The Rift, a first-person shooter blending horror and adventure, where players navigate dark realms and battle monsters
    • College Football 25, a college football simulation game featuring gameplay that mimics real-life college teams and competitions
    • Concepts, a digital sketching app designed for creative professionals, offering flexible drawing tools for illustration, design, and brainstorming
    • Depthkit, a tool for creating and capturing volumetric video, enabling immersive 3D experiences and interactive content
    • IMG.LY, a platform offering creative tools and SDKs for integrating advanced image and video editing in applications
    • LOOT, a tool for optimizing the load order of game plugins, commonly used in The Elder Scrolls and Fallout series
    • Madden NFL 25, a sports simulation game capturing the excitement of American football with realistic gameplay and team management features
    • Marne, an unofficial private server platform for hosting custom Battlefield 1 game experiences
    • Minecraft, a popular sandbox video game
    • NHL 22, a hockey simulation game offering realistic gameplay, team management, and various modes to enhance the hockey experience
    • Pixelpart, a 2D animation and video compositing software that allows users to create animated graphics and visual effects with a focus on simplicity and ease of use
    • Razer Cortex, a gaming performance optimizer and system booster designed to enhance the gaming experience
    • Red Dead Redemption II, an open-world action-adventure game following an outlaw's story in the late 1800s, emphasizing deep storytelling and immersive gameplay
    • Snapchat, a multimedia messaging and augmented reality app for communication and entertainment
    • Tactics Ogre: Reborn, a tactical role-playing game featuring strategic battles and deep storytelling elements
    • Throne and Liberty, an MMORPG that offers an expansive fantasy world with dynamic gameplay and immersive storytelling
    • Unity Vivox, a communication service that enables voice and text chat functionality in multiplayer games developed with Unity
    • Zool: Redimensioned, a modern reimagining of the classic platformer featuring fast-paced gameplay and vibrant environments
    • immersivetech, a technology company focused on immersive experiences, providing tools and solutions for virtual and augmented reality applications

    Consumer Electronics

    • Audinate, a provider of networked audio solutions specializing in Dante technology, which facilitates high-quality digital audio transport over IP networks
    • Canon CanoScan LIDE, a series of flatbed scanners offering high-resolution image scanning for home and office use
    • Canon PIXMA Printers, a line of all-in-one inkjet printers known for high-quality printing and wireless connectivity
    • Cisco Webex Desk Camera, a video camera designed for professional-quality video conferencing and remote collaboration
    • Philips Hue Personal Wireless Lighting, a smart lighting system for customizable and wireless home illumination
    • Ray-Ban Meta Smart glasses, a pair of smart glasses designed for capturing photos and videos with integrated connectivity and social features
    • Razer Synapse, a unified configuration software enabling hardware customization for Razer devices
    • Siemens SINEMA Remote Connect, a remote connectivity solution for monitoring and managing industrial networks and devices securely
    • Sony PlayStation 4, a gaming console developed by Sony that offers a wide range of games and multimedia entertainment features
    • Sony Virtual Webcam Driver for Remote Camera, a software driver that enables the use of Sony cameras as virtual webcams for video conferencing and streaming

    Operating Systems

    • Apple iOS and macOS, a family of operating systems developed by Apple, including iOS for mobile devices and macOS for desktop computers
    • Google Fuchsia, an open-source operating system developed by Google, designed to be secure, updatable, and adaptable across various devices
    • SerenityOS, an open-source operating system that aims to provide a simple and beautiful user experience with a focus on simplicity and elegance
    • Yocto, a Linux-based build system for creating custom operating systems and software distributions, tailored for embedded devices and IoT applications

    Development Tools and IDEs

    • Accentize SpectralBalance, an adaptive speech analysis tool designed to enhance audio quality by optimizing frequency balance in recordings
    • Arm Compiler for Linux, a software development toolchain for compiling and optimizing applications on Arm-based Linux systems
    • BBEdit, a professional text and code editor for macOS
    • CoderPad, a collaborative coding platform that enables real-time code interviews and assessments for developers; the library is included in every CoderPad instance and can be accessed with a simple #include "json.hpp"
    • Compiler Explorer, a web-based tool that allows users to write, compile, and visualize the assembly output of code in various programming languages; the library is readily available and accessible with the directive #include <nlohmann/json.hpp>.
    • GitHub CodeQL, a code analysis tool used for identifying security vulnerabilities and bugs in software through semantic queries
    • Hex-Rays, a reverse engineering toolset for analyzing and decompiling binaries, primarily used for security research and vulnerability analysis
    • ImHex, a hex editor designed for reverse engineering, providing advanced features for data analysis and manipulation
    • Intel GPA Framework, a suite of cross-platform tools for capturing, analyzing, and optimizing graphics applications across different APIs
    • Intopix, a provider of advanced image processing and compression solutions used in software development and AV workflows
    • Java SE, the core Java platform that provides the libraries and runtime needed to build and run general-purpose Java applications
    • MKVToolNix, a set of tools for creating, editing, and inspecting MKV (Matroska) multimedia container files
    • Meta Yoga, a layout engine that facilitates flexible and efficient user interface design across multiple platforms
    • NVIDIA Nsight Compute, a performance analysis tool for CUDA applications that provides detailed insights into GPU performance metrics
    • Notepad++, a free source code editor that supports various programming languages
    • OpenRGB, an open source RGB lighting control that doesn't depend on manufacturer software
    • OpenTelemetry C++, a library for collecting and exporting observability data in C++, enabling developers to implement distributed tracing and metrics in their application
    • Qt Creator, an IDE for developing applications using the Qt application framework
    • Scanbot SDK, a software development kit (SDK) that provides tools for integrating advanced document scanning and barcode scanning capabilities into applications

    Machine Learning and AI

    • Apple Core ML Tools, a set of tools for converting and configuring machine learning models for deployment in Apple's Core ML framework
    • Avular Mobile Robotics, a platform for developing and deploying mobile robotics solutions
    • Google gemma.cpp, a lightweight C++ inference engine designed for running AI models from the Gemma family
    • llama.cpp, a C++ library designed for efficient inference of large language models (LLMs), enabling streamlined integration into applications
    • MLX, an array framework for machine learning on Apple Silicon
    • Mozilla llamafile, a tool designed for distributing and executing large language models (LLMs) efficiently using a single file format
    • NVIDIA ACE, a suite of real-time AI solutions designed for the development of interactive avatars and digital human applications, enabling scalable and sophisticated user interactions
    • Peer, a platform offering personalized AI assistants for interactive learning and creative collaboration
    • stable-diffusion.cpp, a C++ implementation of the Stable Diffusion image generation model
    • TanvasTouch, a software development kit (SDK) that enables developers to create tactile experiences on touchscreens, allowing users to feel textures and physical sensations in a digital environment
    • TensorFlow, a machine learning framework that facilitates the development and training of models, supporting data serialization and efficient data exchange between components

    Scientific Research and Analysis

    • BLACK, a bounded linear temporal logic (LTL) satisfiability checker
    • CERN Atlas Athena, a software framework used in the ATLAS experiment at the Large Hadron Collider (LHC) for performance monitoring
    • ICU, the International Components for Unicode, a mature library for software globalization and multilingual support
    • KAMERA, a platform for synchronized data collection and real-time deep learning to map marine species like polar bears and seals, aiding Arctic ecosystem research
    • KiCad, a free and open-source software suite for electronic design automation
    • Maple, a symbolic and numeric computing environment for advanced mathematical modeling and analysis
    • MeVisLab, a software framework for medical image processing and visualization.
    • OpenPMD API, a versatile programming interface for accessing and managing scientific data, designed to facilitate the efficient storage, retrieval, and sharing of simulation data across various applications and platforms
    • ParaView, an open-source tool for large-scale data visualization and analysis across various scientific domains
    • QGIS, a free and open-source geographic information system (GIS) application that allows users to create, edit, visualize, and analyze geospatial data across a variety of formats
    • VTK, a software library for 3D computer graphics, image processing, and visualization
    • VolView, a lightweight application for interactive visualization and analysis of 3D medical imaging data.

    Business and Productivity Software

    • ArcGIS PRO, a desktop geographic information system (GIS) application developed by Esri for mapping and spatial analysis
    • Autodesk Desktop, a software platform developed by Autodesk for creating and managing desktop applications and services
    • Check Point, a cybersecurity company specializing in threat prevention and network security solutions, offering a range of products designed to protect enterprises from cyber threats and ensure data integrity
    • Microsoft Office for Mac, a suite of productivity applications developed by Microsoft for macOS, including tools for word processing, spreadsheets, and presentations
    • Microsoft Teams, a team collaboration application offering workspace chat and video conferencing, file storage, and integration of proprietary and third-party applications and services
    • Nexthink Infinity, a digital employee experience management platform for monitoring and improving IT performance
    • Sophos Connect Client, a secure VPN client from Sophos that allows remote users to connect to their corporate network, ensuring secure access to resources and data
    • Stonebranch, a cloud-based cybersecurity solution that integrates backup, disaster recovery, and cybersecurity features to protect data and ensure business continuity for organizations
    • Tablecruncher, a data analysis tool that allows users to import, analyze, and visualize spreadsheet data, offering interactive features for better insights and decision-making
    • magicplan, a mobile application for creating floor plans and interior designs using augmented reality

    Databases and Big Data

    • ADIOS2, a data management framework designed for high-performance input and output operations
    • Cribl Stream, a real-time data processing platform that enables organizations to collect, route, and transform observability data, enhancing visibility and insights into their systems
    • DB Browser for SQLite, a visual open-source tool for creating, designing, and editing SQLite database files
    • MySQL Connector/C++, a C++ library for connecting and interacting with MySQL databases
    • MySQL NDB Cluster, a distributed database system that provides high availability and scalability for MySQL databases
    • MySQL Shell, an advanced client and code editor for interacting with MySQL servers, supporting SQL, Python, and JavaScript
    • PrestoDB, a distributed SQL query engine designed for large-scale data analytics, originally developed by Facebook
    • ROOT Data Analysis Framework, an open-source data analysis framework widely used in high-energy physics and other fields for data processing and visualization
    • WiredTiger, a high-performance storage engine for databases, offering support for compression, concurrency, and checkpointing

    Simulation and Modeling

    • Arcturus HoloSuite, a software toolset for capturing, editing, and streaming volumetric video, featuring advanced compression technologies for high-quality 3D content creation
    • azul, a fast and efficient 3D city model viewer designed for visualizing urban environments and spatial data
    • Blender, a free and open-source 3D creation suite for modeling, animation, rendering, and more
    • cpplot, a library for creating interactive graphs and charts in C++, which can be viewed in web browsers
    • Foundry Nuke, a powerful node-based digital compositing and visual effects application used in film and television post-production
    • GAMS, a high-performance mathematical modeling system for optimization and decision support
    • Kitware SMTK, a software toolkit for managing simulation models and workflows in scientific and engineering applications
    • M-Star, a computational fluid dynamics software for simulating and analyzing fluid flow
    • MapleSim CAD Toolbox, a software extension for MapleSim that integrates CAD models, allowing users to import, manipulate, and analyze 3D CAD data within the MapleSim environment for enhanced modeling and simulation
    • NVIDIA Omniverse, a platform for 3D content creation and collaboration that enables real-time simulations and interactive experiences across various industries
    • Pixar Renderman, a photorealistic 3D rendering software developed by Pixar, widely used in the film industry for creating high-quality visual effects and animations
    • ROS - Robot Operating System, a set of software libraries and tools that assist in developing robot applications
    • UBS, a multinational financial services and banking company

    Enterprise and Cloud Applications

    • Acronis Cyber Protect Cloud, an all-in-one data protection solution that combines backup, disaster recovery, and cybersecurity to safeguard business data from threats like ransomware
    • Baereos, a backup solution that provides data protection and recovery options for various environments, including physical and virtual systems
    • Bitdefender Home Scanner, a tool from Bitdefender that scans devices for malware and security threats, providing a safeguard against potential online dangers
    • Citrix Provisioning, a solution that streamlines the delivery of virtual desktops and applications by allowing administrators to manage and provision resources efficiently across multiple environments
    • Citrix Virtual Apps and Desktops, a solution from Citrix that delivers virtual apps and desktops
    • Cyberarc, a security solution that specializes in privileged access management, enabling organizations to control and monitor access to critical systems and data, thereby enhancing overall cybersecurity posture
    • Egnyte Desktop, a secure cloud storage solution designed for businesses, enabling file sharing, collaboration, and data management across teams while ensuring compliance and data protection
    • Elster, a digital platform developed by German tax authorities for secure and efficient electronic tax filing and management using secunet protect4use
    • Ethereum Solidity, a high-level, object-oriented programming language designed for implementing smart contracts on the Ethereum platform
    • Inciga, a monitoring tool for IT infrastructure, designed to provide insights into system performance and availability through customizable dashboards and alerts
    • Intel Accelerator Management Daemon for VMware ESXi, a management tool designed for monitoring and controlling Intel hardware accelerators within VMware ESXi environments, optimizing performance and resource allocation
    • Juniper Identity Management Service
    • Microsoft Azure IoT SDK, a collection of tools and libraries to help developers connect, build, and deploy Internet of Things (IoT) solutions on the Azure cloud platform
    • Microsoft WinGet, a command-line utility included in the Windows Package Manager
    • plexusAV, a high-performance AV-over-IP transceiver device capable of video encoding and decoding using the IPMX standard
    • Pointr, a platform for indoor positioning and navigation solutions, offering tools and SDKs for developers to create location-based applications
    • secunet protect4use, a secure, passwordless multifactor authentication solution that transforms smartphones into digital keyrings, ensuring high security for online services and digital identities
    • Sencore MRD 7000, a professional multi-channel receiver and decoder supporting UHD and HD stream decoding
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Customers - JSON for Modern C++
    Skip to content

    Customers

    The library is used in multiple projects, applications, operating systems, etc. The list below is not exhaustive, but the result of an internet search. If you know further customers of the library, please let me know.

    Space Exploration

    • Peregrine Lunar Lander Flight 01 - The library was used for payload management in the Peregrine Moon Lander, developed by Astrobotic Technology and launched as part of NASA's Commercial Lunar Payload Services (CLPS) program. After six days in orbit, the spacecraft was intentionally redirected into Earth's atmosphere, where it burned up over the Pacific Ocean on January 18, 2024.

    Automotive

    Gaming and Entertainment

    • Assassin's Creed: Mirage, a stealth-action game set in the Middle East, focusing on the journey of a young assassin with classic parkour and stealth mechanics
    • Chasm: The Rift, a first-person shooter blending horror and adventure, where players navigate dark realms and battle monsters
    • College Football 25, a college football simulation game featuring gameplay that mimics real-life college teams and competitions
    • Concepts, a digital sketching app designed for creative professionals, offering flexible drawing tools for illustration, design, and brainstorming
    • Depthkit, a tool for creating and capturing volumetric video, enabling immersive 3D experiences and interactive content
    • IMG.LY, a platform offering creative tools and SDKs for integrating advanced image and video editing in applications
    • LOOT, a tool for optimizing the load order of game plugins, commonly used in The Elder Scrolls and Fallout series
    • Madden NFL 25, a sports simulation game capturing the excitement of American football with realistic gameplay and team management features
    • Marne, an unofficial private server platform for hosting custom Battlefield 1 game experiences
    • Minecraft, a popular sandbox video game
    • NHL 22, a hockey simulation game offering realistic gameplay, team management, and various modes to enhance the hockey experience
    • Pixelpart, a 2D animation and video compositing software that allows users to create animated graphics and visual effects with a focus on simplicity and ease of use
    • Razer Cortex, a gaming performance optimizer and system booster designed to enhance the gaming experience
    • Red Dead Redemption II, an open-world action-adventure game following an outlaw's story in the late 1800s, emphasizing deep storytelling and immersive gameplay
    • Snapchat, a multimedia messaging and augmented reality app for communication and entertainment
    • Tactics Ogre: Reborn, a tactical role-playing game featuring strategic battles and deep storytelling elements
    • Throne and Liberty, an MMORPG that offers an expansive fantasy world with dynamic gameplay and immersive storytelling
    • Unity Vivox, a communication service that enables voice and text chat functionality in multiplayer games developed with Unity
    • Zool: Redimensioned, a modern reimagining of the classic platformer featuring fast-paced gameplay and vibrant environments
    • immersivetech, a technology company focused on immersive experiences, providing tools and solutions for virtual and augmented reality applications

    Consumer Electronics

    • Audinate, a provider of networked audio solutions specializing in Dante technology, which facilitates high-quality digital audio transport over IP networks
    • Canon CanoScan LIDE, a series of flatbed scanners offering high-resolution image scanning for home and office use
    • Canon PIXMA Printers, a line of all-in-one inkjet printers known for high-quality printing and wireless connectivity
    • Cisco Webex Desk Camera, a video camera designed for professional-quality video conferencing and remote collaboration
    • Philips Hue Personal Wireless Lighting, a smart lighting system for customizable and wireless home illumination
    • Ray-Ban Meta Smart glasses, a pair of smart glasses designed for capturing photos and videos with integrated connectivity and social features
    • Razer Synapse, a unified configuration software enabling hardware customization for Razer devices
    • Siemens SINEMA Remote Connect, a remote connectivity solution for monitoring and managing industrial networks and devices securely
    • Sony PlayStation 4, a gaming console developed by Sony that offers a wide range of games and multimedia entertainment features
    • Sony Virtual Webcam Driver for Remote Camera, a software driver that enables the use of Sony cameras as virtual webcams for video conferencing and streaming

    Operating Systems

    • Apple iOS and macOS, a family of operating systems developed by Apple, including iOS for mobile devices and macOS for desktop computers
    • Google Fuchsia, an open-source operating system developed by Google, designed to be secure, updatable, and adaptable across various devices
    • SerenityOS, an open-source operating system that aims to provide a simple and beautiful user experience with a focus on simplicity and elegance
    • Yocto, a Linux-based build system for creating custom operating systems and software distributions, tailored for embedded devices and IoT applications

    Development Tools and IDEs

    • Accentize SpectralBalance, an adaptive speech analysis tool designed to enhance audio quality by optimizing frequency balance in recordings
    • Arm Compiler for Linux, a software development toolchain for compiling and optimizing applications on Arm-based Linux systems
    • BBEdit, a professional text and code editor for macOS
    • CoderPad, a collaborative coding platform that enables real-time code interviews and assessments for developers; the library is included in every CoderPad instance and can be accessed with a simple #include "json.hpp"
    • Compiler Explorer, a web-based tool that allows users to write, compile, and visualize the assembly output of code in various programming languages; the library is readily available and accessible with the directive #include <nlohmann/json.hpp>.
    • GitHub CodeQL, a code analysis tool used for identifying security vulnerabilities and bugs in software through semantic queries
    • Hex-Rays, a reverse engineering toolset for analyzing and decompiling binaries, primarily used for security research and vulnerability analysis
    • ImHex, a hex editor designed for reverse engineering, providing advanced features for data analysis and manipulation
    • Intel GPA Framework, a suite of cross-platform tools for capturing, analyzing, and optimizing graphics applications across different APIs
    • Intopix, a provider of advanced image processing and compression solutions used in software development and AV workflows
    • Java SE, the core Java platform that provides the libraries and runtime needed to build and run general-purpose Java applications
    • MKVToolNix, a set of tools for creating, editing, and inspecting MKV (Matroska) multimedia container files
    • Meta Yoga, a layout engine that facilitates flexible and efficient user interface design across multiple platforms
    • NVIDIA Nsight Compute, a performance analysis tool for CUDA applications that provides detailed insights into GPU performance metrics
    • Notepad++, a free source code editor that supports various programming languages
    • OpenRGB, an open source RGB lighting control that doesn't depend on manufacturer software
    • OpenTelemetry C++, a library for collecting and exporting observability data in C++, enabling developers to implement distributed tracing and metrics in their application
    • Qt Creator, an IDE for developing applications using the Qt application framework
    • Scanbot SDK, a software development kit (SDK) that provides tools for integrating advanced document scanning and barcode scanning capabilities into applications

    Machine Learning and AI

    • Apple Core ML Tools, a set of tools for converting and configuring machine learning models for deployment in Apple's Core ML framework
    • Avular Mobile Robotics, a platform for developing and deploying mobile robotics solutions
    • Google gemma.cpp, a lightweight C++ inference engine designed for running AI models from the Gemma family
    • llama.cpp, a C++ library designed for efficient inference of large language models (LLMs), enabling streamlined integration into applications
    • MLX, an array framework for machine learning on Apple Silicon
    • Mozilla llamafile, a tool designed for distributing and executing large language models (LLMs) efficiently using a single file format
    • NVIDIA ACE, a suite of real-time AI solutions designed for the development of interactive avatars and digital human applications, enabling scalable and sophisticated user interactions
    • Peer, a platform offering personalized AI assistants for interactive learning and creative collaboration
    • stable-diffusion.cpp, a C++ implementation of the Stable Diffusion image generation model
    • TanvasTouch, a software development kit (SDK) that enables developers to create tactile experiences on touchscreens, allowing users to feel textures and physical sensations in a digital environment
    • TensorFlow, a machine learning framework that facilitates the development and training of models, supporting data serialization and efficient data exchange between components

    Scientific Research and Analysis

    • BLACK, a bounded linear temporal logic (LTL) satisfiability checker
    • CERN Atlas Athena, a software framework used in the ATLAS experiment at the Large Hadron Collider (LHC) for performance monitoring
    • ICU, the International Components for Unicode, a mature library for software globalization and multilingual support
    • KAMERA, a platform for synchronized data collection and real-time deep learning to map marine species like polar bears and seals, aiding Arctic ecosystem research
    • KiCad, a free and open-source software suite for electronic design automation
    • Maple, a symbolic and numeric computing environment for advanced mathematical modeling and analysis
    • MeVisLab, a software framework for medical image processing and visualization.
    • OpenPMD API, a versatile programming interface for accessing and managing scientific data, designed to facilitate the efficient storage, retrieval, and sharing of simulation data across various applications and platforms
    • ParaView, an open-source tool for large-scale data visualization and analysis across various scientific domains
    • QGIS, a free and open-source geographic information system (GIS) application that allows users to create, edit, visualize, and analyze geospatial data across a variety of formats
    • VTK, a software library for 3D computer graphics, image processing, and visualization
    • VolView, a lightweight application for interactive visualization and analysis of 3D medical imaging data.

    Business and Productivity Software

    • ArcGIS PRO, a desktop geographic information system (GIS) application developed by Esri for mapping and spatial analysis
    • Autodesk Desktop, a software platform developed by Autodesk for creating and managing desktop applications and services
    • Check Point, a cybersecurity company specializing in threat prevention and network security solutions, offering a range of products designed to protect enterprises from cyber threats and ensure data integrity
    • Microsoft Office for Mac, a suite of productivity applications developed by Microsoft for macOS, including tools for word processing, spreadsheets, and presentations
    • Microsoft Teams, a team collaboration application offering workspace chat and video conferencing, file storage, and integration of proprietary and third-party applications and services
    • Nexthink Infinity, a digital employee experience management platform for monitoring and improving IT performance
    • Sophos Connect Client, a secure VPN client from Sophos that allows remote users to connect to their corporate network, ensuring secure access to resources and data
    • Stonebranch, a cloud-based cybersecurity solution that integrates backup, disaster recovery, and cybersecurity features to protect data and ensure business continuity for organizations
    • Tablecruncher, a data analysis tool that allows users to import, analyze, and visualize spreadsheet data, offering interactive features for better insights and decision-making
    • magicplan, a mobile application for creating floor plans and interior designs using augmented reality

    Databases and Big Data

    • ADIOS2, a data management framework designed for high-performance input and output operations
    • Cribl Stream, a real-time data processing platform that enables organizations to collect, route, and transform observability data, enhancing visibility and insights into their systems
    • DB Browser for SQLite, a visual open-source tool for creating, designing, and editing SQLite database files
    • MySQL Connector/C++, a C++ library for connecting and interacting with MySQL databases
    • MySQL NDB Cluster, a distributed database system that provides high availability and scalability for MySQL databases
    • MySQL Shell, an advanced client and code editor for interacting with MySQL servers, supporting SQL, Python, and JavaScript
    • PrestoDB, a distributed SQL query engine designed for large-scale data analytics, originally developed by Facebook
    • ROOT Data Analysis Framework, an open-source data analysis framework widely used in high-energy physics and other fields for data processing and visualization
    • WiredTiger, a high-performance storage engine for databases, offering support for compression, concurrency, and checkpointing

    Simulation and Modeling

    • Arcturus HoloSuite, a software toolset for capturing, editing, and streaming volumetric video, featuring advanced compression technologies for high-quality 3D content creation
    • azul, a fast and efficient 3D city model viewer designed for visualizing urban environments and spatial data
    • Blender, a free and open-source 3D creation suite for modeling, animation, rendering, and more
    • cpplot, a library for creating interactive graphs and charts in C++, which can be viewed in web browsers
    • Foundry Nuke, a powerful node-based digital compositing and visual effects application used in film and television post-production
    • GAMS, a high-performance mathematical modeling system for optimization and decision support
    • Kitware SMTK, a software toolkit for managing simulation models and workflows in scientific and engineering applications
    • M-Star, a computational fluid dynamics software for simulating and analyzing fluid flow
    • MapleSim CAD Toolbox, a software extension for MapleSim that integrates CAD models, allowing users to import, manipulate, and analyze 3D CAD data within the MapleSim environment for enhanced modeling and simulation
    • NVIDIA Omniverse, a platform for 3D content creation and collaboration that enables real-time simulations and interactive experiences across various industries
    • Pixar Renderman, a photorealistic 3D rendering software developed by Pixar, widely used in the film industry for creating high-quality visual effects and animations
    • ROS - Robot Operating System, a set of software libraries and tools that assist in developing robot applications
    • UBS, a multinational financial services and banking company

    Enterprise and Cloud Applications

    • Acronis Cyber Protect Cloud, an all-in-one data protection solution that combines backup, disaster recovery, and cybersecurity to safeguard business data from threats like ransomware
    • Baereos, a backup solution that provides data protection and recovery options for various environments, including physical and virtual systems
    • Bitdefender Home Scanner, a tool from Bitdefender that scans devices for malware and security threats, providing a safeguard against potential online dangers
    • Citrix Provisioning, a solution that streamlines the delivery of virtual desktops and applications by allowing administrators to manage and provision resources efficiently across multiple environments
    • Citrix Virtual Apps and Desktops, a solution from Citrix that delivers virtual apps and desktops
    • Cyberarc, a security solution that specializes in privileged access management, enabling organizations to control and monitor access to critical systems and data, thereby enhancing overall cybersecurity posture
    • Egnyte Desktop, a secure cloud storage solution designed for businesses, enabling file sharing, collaboration, and data management across teams while ensuring compliance and data protection
    • Elster, a digital platform developed by German tax authorities for secure and efficient electronic tax filing and management using secunet protect4use
    • Ethereum Solidity, a high-level, object-oriented programming language designed for implementing smart contracts on the Ethereum platform
    • Inciga, a monitoring tool for IT infrastructure, designed to provide insights into system performance and availability through customizable dashboards and alerts
    • Intel Accelerator Management Daemon for VMware ESXi, a management tool designed for monitoring and controlling Intel hardware accelerators within VMware ESXi environments, optimizing performance and resource allocation
    • Juniper Identity Management Service
    • Microsoft Azure IoT SDK, a collection of tools and libraries to help developers connect, build, and deploy Internet of Things (IoT) solutions on the Azure cloud platform
    • Microsoft WinGet, a command-line utility included in the Windows Package Manager
    • plexusAV, a high-performance AV-over-IP transceiver device capable of video encoding and decoding using the IPMX standard
    • Pointr, a platform for indoor positioning and navigation solutions, offering tools and SDKs for developers to create location-based applications
    • secunet protect4use, a secure, passwordless multifactor authentication solution that transforms smartphones into digital keyrings, ensuring high security for online services and digital identities
    • Sencore MRD 7000, a professional multi-channel receiver and decoder supporting UHD and HD stream decoding
    Copyright © 2013-2026 Niels Lohmann
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    Design goals

    There are myriads of JSON libraries out there, and each may even have its reason to exist. Our class had these design goals:

    • Intuitive syntax. In languages such as Python, JSON feels like a first-class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code.

    • Trivial integration. Our whole code consists of a single header file json.hpp. That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.

    • Serious testing. Our class is heavily unit-tested and covers 100% of the code, including all exceptional behavior. Furthermore, we checked with Valgrind and the Clang Sanitizers that there are no memory leaks. Google OSS-Fuzz additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the Core Infrastructure Initiative (CII) best practices.

    Other aspects were not so important to us:

    • Memory efficiency. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: std::string for strings, int64_t, uint64_t or double for numbers, std::map for objects, std::vector for arrays, and bool for Booleans. However, you can template the generalized class basic_json to your needs.

    • Speed. There are certainly faster JSON libraries out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a std::vector or std::map, you are already set.

    See the contribution guidelines for more information.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Design goals - JSON for Modern C++
    Skip to content

    Design goals

    There are myriads of JSON libraries out there, and each may even have its reason to exist. Our class had these design goals:

    • Intuitive syntax. In languages such as Python, JSON feels like a first-class data type. We used all the operator magic of modern C++ to achieve the same feeling in your code.

    • Trivial integration. Our whole code consists of a single header file json.hpp. That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.

    • Serious testing. Our class is heavily unit-tested and covers 100% of the code, including all exceptional behavior. Furthermore, we checked with Valgrind and the Clang Sanitizers that there are no memory leaks. Google OSS-Fuzz additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the Core Infrastructure Initiative (CII) best practices.

    Other aspects were not so important to us:

    • Memory efficiency. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: std::string for strings, int64_t, uint64_t or double for numbers, std::map for objects, std::vector for arrays, and bool for Booleans. However, you can template the generalized class basic_json to your needs.

    • Speed. There are certainly faster JSON libraries out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a std::vector or std::map, you are already set.

    See the contribution guidelines for more information.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/home/exceptions/index.html b/home/exceptions/index.html index 24881e7fd..992bd5edd 100644 --- a/home/exceptions/index.html +++ b/home/exceptions/index.html @@ -284,4 +284,4 @@ array index 18446744073709551616 exceeds size_type

    Output:

    message: [json.exception.other_error.501] unsuccessful: {"op":"test","path":"/best_biscuit/name","value":"Choco Leibniz"}
 exception id: 501

    json.exception.other_error.501

    A JSON Patch operation 'test' failed. The unsuccessful operation is also printed.

    Example message

    Executing {"op":"test", "path":"/baz", "value":"bar"} on {"baz": "qux"}:

    [json.exception.other_error.501] unsuccessful: {"op":"test","path":"/baz","value":"bar"}
-
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    Exceptions

    Parsing without exceptions

    Question

    Is it possible to indicate a parse error without throwing an exception?

    Yes, see Parsing and exceptions.

    Key name in exceptions

    Question

    Can I get the key of the object item that caused an exception?

    Yes, you can. Please define the symbol JSON_DIAGNOSTICS to get extended diagnostics messages.

    Serialization issues

    Number precision

    Question

    The library uses std::numeric_limits<number_float_t>::digits10 (15 for IEEE doubles) digits for serialization. This value is sufficient to guarantee roundtripping. If one uses more than this number of digits of precision, then string -> value -> string is not guaranteed to round-trip.

    cppreference.com

    The value of std::numeric_limits<T>::digits10 is the number of base-10 digits that can be represented by the type T without change, that is, any number with this many significant decimal digits can be converted to a value of type T and back to decimal form, without change due to rounding or overflow.

    Tip

    The website https://float.exposed gives a good insight into the internal storage of floating-point numbers.

    See this section on the library's number handling for more information.

    Using JSON values with std::format or fmt

    Question

    std::format works out of the box since version 3.13.0, as long as the standard library provides <format> (see JSON_HAS_STD_FORMAT); see std::formatter<basic_json> for details, including the "{:#}" pretty-print spec, indent widths ("{:2}"), and custom indent characters ("{:.>#}").

    For fmt, the library ships format_as, a small customization point fmt looks for via argument-dependent lookup. It only has an effect on fmt 10.0.0 through 11.0.2 — from fmt 11.1.0 onwards, fmt no longer picks up a format_as overload that returns a std::string. On such versions (or any version, if you also want the same "{:#}"/width/fill-and-align spec support that std::formatter<basic_json> has), define your own fmt::formatter specialization; see format_as for a recipe that mirrors it.

    If you get ambiguous-overload errors when passing a JSON value to fmt::format/fmt::print without any fmt::formatter<json> specialization in scope, that's fmt picking up basic_json's implicit operator ValueType() conversion operator (see #964 and #958); disabling it via JSON_USE_IMPLICIT_CONVERSIONS 0 avoids the ambiguity.

    Compilation issues

    Android SDK

    Question

    Why does the code not compile with Android SDK?

    Android defaults to using very old compilers and C++ libraries. To fix this, add the following to your Application.mk. This will switch to the LLVM C++ library, the Clang compiler, and enable C++11 and other features disabled by default.

    APP_STL := c++_shared
 NDK_TOOLCHAIN_VERSION := clang3.6
 APP_CPPFLAGS += -frtti -fexceptions
-

    The code compiles successfully with Android NDK, Revision 9 - 11 (and possibly later) and CrystaX's Android NDK version 10.

    Missing STL function

    Questions

    This is not an issue with the code, but rather with the compiler itself. On Android, see above to build with a newer environment. For MinGW, please refer to this site and this discussion for information on how to fix this bug. For Android NDK using APP_STL := gnustl_static, please refer to this discussion.

    \ No newline at end of file +

    The code compiles successfully with Android NDK, Revision 9 - 11 (and possibly later) and CrystaX's Android NDK version 10.

    Missing STL function

    Questions

    This is not an issue with the code, but rather with the compiler itself. On Android, see above to build with a newer environment. For MinGW, please refer to this site and this discussion for information on how to fix this bug. For Android NDK using APP_STL := gnustl_static, please refer to this discussion.

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    Skip to content

    License

    The class is licensed under the MIT License:

    Copyright © 2013-2026 Niels Lohmann

    Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed under the MIT License (see above). Copyright © 2008-2009 Björn Hoehrmann bjoern@hoehrmann.de

    The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the MIT License (see above). Copyright © 2009 Florian Loitsch

    The class contains a copy of Hedley from Evan Nemerson which is licensed as CC0-1.0.

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + License - JSON for Modern C++
    Skip to content

    License

    The class is licensed under the MIT License:

    Copyright © 2013-2026 Niels Lohmann

    Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    The class contains the UTF-8 Decoder from Bjoern Hoehrmann which is licensed under the MIT License (see above). Copyright © 2008-2009 Björn Hoehrmann bjoern@hoehrmann.de

    The class contains a slightly modified version of the Grisu2 algorithm from Florian Loitsch which is licensed under the MIT License (see above). Copyright © 2009 Florian Loitsch

    The class contains a copy of Hedley from Evan Nemerson which is licensed as CC0-1.0.

    Copyright © 2013-2026 Niels Lohmann
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    Releases

    This page summarizes the notable changes of every release and links to the relevant documentation. The complete release notes — including all changes, the download files, and their checksums — are published on the GitHub releases page.

    v3.12.0 (2025-04-11)

    Fixes bugs found in 3.11.3 and adds several features. All changes are backward-compatible.

    Full release notes.

    v3.11.3 (2023-11-28)

    Adds features and fixes bugs found in 3.11.2. All changes are backward-compatible.

    • Adds a custom base class as a node customization point.
    • Adds serialization-only conversion macros (NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE and NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE) and a clearer parse error for empty input.
    • Adds Bazel and Swift Package Manager build support.
    • Fixes custom allocators, a memory leak in adl_serializer's to_json, initializer-list construction when size_type is not int, and many compiler warnings.

    Full release notes.

    v3.11.2 (2022-08-12)

    Fixes bugs found in 3.11.1 and restructures the namespace. All changes are backward-compatible.

    • Fixes the value function (broken for strings, size types, and nullptr in 3.11.0) and makes json_fwd.hpp self-contained.
    • Restores using json_pointer as a key in associative containers and comparing it with strings.
    • Restructures the inline namespace and allows disabling the version component, and avoids heap allocations in the BJData parser.

    Full release notes.

    v3.11.1 (2022-08-01)

    Fixes a regression from 3.11.0. All changes are backward-compatible.

    Full release notes.

    v3.11.0 (2022-08-01)

    One of the largest releases ever. All changes are backward-compatible.

    This release introduced a UDL regression that was fixed in 3.11.1. Full release notes.

    v3.10.5 (2022-01-03)

    Bug-fix release. All changes are backward-compatible.

    • Guards the std::filesystem conversions behind compiler-support checks (JSON_HAS_FILESYSTEM), which can be set to 0 to disable them altogether.

    Full release notes.

    v3.10.4 (2021-10-16)

    Fixes regressions introduced in 3.10.0. All changes are backward-compatible.

    • Fixes the std::filesystem::path conversion (which could trigger a stack overflow and broke compilation on Windows).
    • Fixes compilation for types with an explicit defaulted constructor and for code relying on the return values of std::find and std::remove.

    Full release notes.

    v3.10.3 (2021-10-08)

    Fixes more regressions from 3.10.0. All changes are backward-compatible.

    • Fixes extended-diagnostics assertions triggered by update and by inserting into arrays.
    • Supports custom allocators when writing binary formats into a std::vector, and allows conversion from types that only provide begin()/end().

    Full release notes.

    v3.10.2 (2021-08-26)

    Re-release of 3.10.1, whose Git tag pointed at the wrong commit due to a bug in the release script. All changes are backward-compatible. Full release notes.

    v3.10.1 (2021-08-24)

    Fixes a regression from 3.10.0. All changes are backward-compatible.

    Full release notes.

    v3.10.0 (2021-08-17)

    Feature release. All changes are backward-compatible.

    • Adds extended diagnostic messages (JSON_DIAGNOSTICS) that prepend a JSON pointer to exception messages to pinpoint the offending value.
    • Adds a GDB pretty-printer and a cbor_tag_handler_t store option to keep CBOR tags as binary subtypes.
    • Supports containers with non-default-constructible types and parsing from std::byte.
    • Adds JSON_NO_IO to exclude the I/O headers and the JSON_HAS_CPP_* macros to override the detected C++ standard.

    Full release notes.

    v3.9.1 (2020-08-06)

    Fixes two regressions from 3.9.0. All changes are backward-compatible.

    Full release notes.

    v3.9.0 (2020-07-27)

    Feature release adding four long-requested features. All changes are backward-compatible.

    Full release notes.

    v3.8.0 (2020-06-14)

    Feature release. All changes are backward-compatible.

    • Introduces a binary value type that is read from and written to CBOR, BSON, and MessagePack, and can be shared between formats.
    • Generalizes the input adapters to read from any LegacyInputIterator container (3–10 % faster parsing).
    • Fixes contains for JSON pointers and makes the binary from_cbor/from_msgpack/etc. functions respect allow_exceptions.

    Full release notes.

    v3.7.3 (2019-11-17)

    Fixes a regression from 3.7.2 that could yield quadratic complexity in destructor calls. All changes are backward-compatible. Full release notes.

    v3.7.2 (2019-11-10)

    Fixes a stack overflow for deeply nested input by making the destructor iterative; parsing is now bounded only by available memory. All changes are backward-compatible. Full release notes.

    v3.7.1 (2019-11-06)

    Bug-fix release. All changes are backward-compatible.

    • Fixes a segmentation fault when serializing the std::int64_t minimum value and fixes contains for JSON pointers.
    • Allows items with a custom string type and makes json_pointer::back const.

    Full release notes.

    v3.7.0 (2019-07-28)

    Convenience features and house-keeping. All changes are backward-compatible.

    • Adds a contains overload that checks a JSON pointer without throwing, a generic to_string, and a return value for emplace_back.

    Full release notes.

    v3.6.1 (2019-03-20)

    Fixes a regression (GCC 7/8 compilation) and a <Windows.h> build error introduced in 3.6.0. All changes are backward-compatible. Full release notes.

    v3.6.0 (2019-03-20)

    Feature release. All changes are backward-compatible.

    • Reworks the JSON pointer interface (operator/, push_back, parent_pointer, …).
    • Adds a contains function to test for an object key and greatly improves the performance of integer serialization.

    Full release notes.

    v3.5.0 (2018-12-22)

    Feature release. All changes are backward-compatible.

    • Adds structured-binding support via the items function and reading from FILE* in the parse function.
    • Fixes the eofbit handling on input streams and a bug in the BSON SAX parser.

    Full release notes.

    v3.4.0 (2018-10-30)

    Feature release. All changes are backward-compatible.

    Full release notes.

    v3.3.0 (2018-10-05)

    Feature release. All changes are backward-compatible.

    • Adds GCC 4.8 support, the get_to function, and an overhauled and documented CMake integration.

    Full release notes.

    v3.2.0 (2018-08-20)

    Feature release. All changes are backward-compatible.

    • Adds a SAX interface and a non-recursive parser.
    • Adds parsing from wide-string types (std::wstring, std::u16string, std::u32string) and std::string_view (C++17), and round-tripping of std::map/std::unordered_map with non-string keys.

    Full release notes.

    v3.1.2 (2018-03-14)

    Bug-fix release. All changes are backward-compatible.

    • Fixes a memory leak in the parser callback and adds user-defined string-type support to the parser and serializer.

    Full release notes.

    v3.1.1 (2018-02-13)

    Bug-fix release. All changes are backward-compatible.

    • Fixes parsing of indefinite-length CBOR strings, a user-defined conversion to vector types, and overflow detection for UBJSON containers.

    Full release notes.

    v3.1.0 (2018-02-01)

    Feature release. All changes are backward-compatible.

    Full release notes.

    v3.0.1 (2017-12-29)

    Fixes small issues in the JSON Pointer and JSON Patch implementations (invalid "copy" targets and non-integer array indices). All changes are backward-compatible. Full release notes.

    v3.0.0 (2017-12-17)

    First 3.x release — a major release with breaking changes (see the migration guide).

    • Introduces user-defined exceptions (json::exception and subtypes, each with an identifier).
    • Adds a non-throwing accept function and an allow_exceptions flag for parse, and an update function to merge objects.
    • Adds streaming for CBOR and MessagePack and allows storing NaN/infinity.
    • Non-UTF-8 strings now throw on serialization, and the iterator category changed to bidirectional.

    Full release notes.

    v2.1.1 (2017-02-25)

    Bug-fix release. All changes are backward-compatible.

    • Makes number parsing and serialization locale-independent with correct floating-point round-tripping; released files are now GPG-signed.

    Full release notes.

    v2.1.0 (2017-01-28)

    Feature release. All changes are backward-compatible.

    Full release notes.

    v2.0.10 (2017-01-02)

    Fixes several security-relevant bugs in the CBOR and MessagePack parsers found by OSS-Fuzz. All changes are backward-compatible. Full release notes.

    v2.0.9 (2016-12-16)

    Adds the CBOR and MessagePack binary formats. All changes are backward-compatible. Full release notes.

    v2.0.8 (2016-12-02)

    Adds the emplace and emplace_back functions and improves parsing and serialization performance. All changes are backward-compatible. Full release notes.

    v2.0.7 (2016-11-02)

    Fixes several parser bugs found through the "Parsing JSON is a Minefield" study (short files, encoding detection, surrogate pairs). All changes are backward-compatible. Full release notes.

    v2.0.6 (2016-10-15)

    Fixes operator[] for JSON pointers so that it creates missing values like the other overloads. All changes are backward-compatible. Full release notes.

    v2.0.5 (2016-09-14)

    Fixes a remaining stream end-of-file detection bug in the parser. All changes are backward-compatible. Full release notes.

    v2.0.4 (2016-09-11)

    Fixes stream end-of-file detection in the parser. All changes are backward-compatible. Full release notes.

    v2.0.3 (2016-08-31)

    Generalizes the parser to accept any contiguous sequence of one-byte elements and deprecates the input-stream constructor in favor of the parse function. All changes are backward-compatible. Full release notes.

    v2.0.2 (2016-07-31)

    Overhauls the parser (now rejecting unescaped control characters), tightens the class invariants, and cleans up the code. All changes are backward-compatible. Full release notes.

    v2.0.1 (2016-06-28)

    Fixes a performance regression in the dump function by adjusting the stream locale once per serialization. All changes are backward-compatible. Full release notes.

    v2.0.0 (2016-06-24)

    Feature release with a minor (potentially non-backward-compatible) API change from added noexcept and constexpr specifiers.

    Full release notes.

    v1.1.0 (2016-01-24)

    Bug-fix and feature release. All changes are backward-compatible.

    • Improves floating-point round-tripping, adds a get_ref accessor for stored values, and introduces runtime assertions.

    Full release notes.

    v1.0.0 (2015-12-28)

    First official release. Full release notes.

    See also

    • Migration Guide — how to future-proof your code for the next major version and replace deprecated functions.
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Releases - JSON for Modern C++
    Skip to content

    Releases

    This page summarizes the notable changes of every release and links to the relevant documentation. The complete release notes — including all changes, the download files, and their checksums — are published on the GitHub releases page.

    v3.12.0 (2025-04-11)

    Fixes bugs found in 3.11.3 and adds several features. All changes are backward-compatible.

    Full release notes.

    v3.11.3 (2023-11-28)

    Adds features and fixes bugs found in 3.11.2. All changes are backward-compatible.

    • Adds a custom base class as a node customization point.
    • Adds serialization-only conversion macros (NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE and NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE) and a clearer parse error for empty input.
    • Adds Bazel and Swift Package Manager build support.
    • Fixes custom allocators, a memory leak in adl_serializer's to_json, initializer-list construction when size_type is not int, and many compiler warnings.

    Full release notes.

    v3.11.2 (2022-08-12)

    Fixes bugs found in 3.11.1 and restructures the namespace. All changes are backward-compatible.

    • Fixes the value function (broken for strings, size types, and nullptr in 3.11.0) and makes json_fwd.hpp self-contained.
    • Restores using json_pointer as a key in associative containers and comparing it with strings.
    • Restructures the inline namespace and allows disabling the version component, and avoids heap allocations in the BJData parser.

    Full release notes.

    v3.11.1 (2022-08-01)

    Fixes a regression from 3.11.0. All changes are backward-compatible.

    Full release notes.

    v3.11.0 (2022-08-01)

    One of the largest releases ever. All changes are backward-compatible.

    This release introduced a UDL regression that was fixed in 3.11.1. Full release notes.

    v3.10.5 (2022-01-03)

    Bug-fix release. All changes are backward-compatible.

    • Guards the std::filesystem conversions behind compiler-support checks (JSON_HAS_FILESYSTEM), which can be set to 0 to disable them altogether.

    Full release notes.

    v3.10.4 (2021-10-16)

    Fixes regressions introduced in 3.10.0. All changes are backward-compatible.

    • Fixes the std::filesystem::path conversion (which could trigger a stack overflow and broke compilation on Windows).
    • Fixes compilation for types with an explicit defaulted constructor and for code relying on the return values of std::find and std::remove.

    Full release notes.

    v3.10.3 (2021-10-08)

    Fixes more regressions from 3.10.0. All changes are backward-compatible.

    • Fixes extended-diagnostics assertions triggered by update and by inserting into arrays.
    • Supports custom allocators when writing binary formats into a std::vector, and allows conversion from types that only provide begin()/end().

    Full release notes.

    v3.10.2 (2021-08-26)

    Re-release of 3.10.1, whose Git tag pointed at the wrong commit due to a bug in the release script. All changes are backward-compatible. Full release notes.

    v3.10.1 (2021-08-24)

    Fixes a regression from 3.10.0. All changes are backward-compatible.

    Full release notes.

    v3.10.0 (2021-08-17)

    Feature release. All changes are backward-compatible.

    • Adds extended diagnostic messages (JSON_DIAGNOSTICS) that prepend a JSON pointer to exception messages to pinpoint the offending value.
    • Adds a GDB pretty-printer and a cbor_tag_handler_t store option to keep CBOR tags as binary subtypes.
    • Supports containers with non-default-constructible types and parsing from std::byte.
    • Adds JSON_NO_IO to exclude the I/O headers and the JSON_HAS_CPP_* macros to override the detected C++ standard.

    Full release notes.

    v3.9.1 (2020-08-06)

    Fixes two regressions from 3.9.0. All changes are backward-compatible.

    Full release notes.

    v3.9.0 (2020-07-27)

    Feature release adding four long-requested features. All changes are backward-compatible.

    Full release notes.

    v3.8.0 (2020-06-14)

    Feature release. All changes are backward-compatible.

    • Introduces a binary value type that is read from and written to CBOR, BSON, and MessagePack, and can be shared between formats.
    • Generalizes the input adapters to read from any LegacyInputIterator container (3–10 % faster parsing).
    • Fixes contains for JSON pointers and makes the binary from_cbor/from_msgpack/etc. functions respect allow_exceptions.

    Full release notes.

    v3.7.3 (2019-11-17)

    Fixes a regression from 3.7.2 that could yield quadratic complexity in destructor calls. All changes are backward-compatible. Full release notes.

    v3.7.2 (2019-11-10)

    Fixes a stack overflow for deeply nested input by making the destructor iterative; parsing is now bounded only by available memory. All changes are backward-compatible. Full release notes.

    v3.7.1 (2019-11-06)

    Bug-fix release. All changes are backward-compatible.

    • Fixes a segmentation fault when serializing the std::int64_t minimum value and fixes contains for JSON pointers.
    • Allows items with a custom string type and makes json_pointer::back const.

    Full release notes.

    v3.7.0 (2019-07-28)

    Convenience features and house-keeping. All changes are backward-compatible.

    • Adds a contains overload that checks a JSON pointer without throwing, a generic to_string, and a return value for emplace_back.

    Full release notes.

    v3.6.1 (2019-03-20)

    Fixes a regression (GCC 7/8 compilation) and a <Windows.h> build error introduced in 3.6.0. All changes are backward-compatible. Full release notes.

    v3.6.0 (2019-03-20)

    Feature release. All changes are backward-compatible.

    • Reworks the JSON pointer interface (operator/, push_back, parent_pointer, …).
    • Adds a contains function to test for an object key and greatly improves the performance of integer serialization.

    Full release notes.

    v3.5.0 (2018-12-22)

    Feature release. All changes are backward-compatible.

    • Adds structured-binding support via the items function and reading from FILE* in the parse function.
    • Fixes the eofbit handling on input streams and a bug in the BSON SAX parser.

    Full release notes.

    v3.4.0 (2018-10-30)

    Feature release. All changes are backward-compatible.

    Full release notes.

    v3.3.0 (2018-10-05)

    Feature release. All changes are backward-compatible.

    • Adds GCC 4.8 support, the get_to function, and an overhauled and documented CMake integration.

    Full release notes.

    v3.2.0 (2018-08-20)

    Feature release. All changes are backward-compatible.

    • Adds a SAX interface and a non-recursive parser.
    • Adds parsing from wide-string types (std::wstring, std::u16string, std::u32string) and std::string_view (C++17), and round-tripping of std::map/std::unordered_map with non-string keys.

    Full release notes.

    v3.1.2 (2018-03-14)

    Bug-fix release. All changes are backward-compatible.

    • Fixes a memory leak in the parser callback and adds user-defined string-type support to the parser and serializer.

    Full release notes.

    v3.1.1 (2018-02-13)

    Bug-fix release. All changes are backward-compatible.

    • Fixes parsing of indefinite-length CBOR strings, a user-defined conversion to vector types, and overflow detection for UBJSON containers.

    Full release notes.

    v3.1.0 (2018-02-01)

    Feature release. All changes are backward-compatible.

    Full release notes.

    v3.0.1 (2017-12-29)

    Fixes small issues in the JSON Pointer and JSON Patch implementations (invalid "copy" targets and non-integer array indices). All changes are backward-compatible. Full release notes.

    v3.0.0 (2017-12-17)

    First 3.x release — a major release with breaking changes (see the migration guide).

    • Introduces user-defined exceptions (json::exception and subtypes, each with an identifier).
    • Adds a non-throwing accept function and an allow_exceptions flag for parse, and an update function to merge objects.
    • Adds streaming for CBOR and MessagePack and allows storing NaN/infinity.
    • Non-UTF-8 strings now throw on serialization, and the iterator category changed to bidirectional.

    Full release notes.

    v2.1.1 (2017-02-25)

    Bug-fix release. All changes are backward-compatible.

    • Makes number parsing and serialization locale-independent with correct floating-point round-tripping; released files are now GPG-signed.

    Full release notes.

    v2.1.0 (2017-01-28)

    Feature release. All changes are backward-compatible.

    Full release notes.

    v2.0.10 (2017-01-02)

    Fixes several security-relevant bugs in the CBOR and MessagePack parsers found by OSS-Fuzz. All changes are backward-compatible. Full release notes.

    v2.0.9 (2016-12-16)

    Adds the CBOR and MessagePack binary formats. All changes are backward-compatible. Full release notes.

    v2.0.8 (2016-12-02)

    Adds the emplace and emplace_back functions and improves parsing and serialization performance. All changes are backward-compatible. Full release notes.

    v2.0.7 (2016-11-02)

    Fixes several parser bugs found through the "Parsing JSON is a Minefield" study (short files, encoding detection, surrogate pairs). All changes are backward-compatible. Full release notes.

    v2.0.6 (2016-10-15)

    Fixes operator[] for JSON pointers so that it creates missing values like the other overloads. All changes are backward-compatible. Full release notes.

    v2.0.5 (2016-09-14)

    Fixes a remaining stream end-of-file detection bug in the parser. All changes are backward-compatible. Full release notes.

    v2.0.4 (2016-09-11)

    Fixes stream end-of-file detection in the parser. All changes are backward-compatible. Full release notes.

    v2.0.3 (2016-08-31)

    Generalizes the parser to accept any contiguous sequence of one-byte elements and deprecates the input-stream constructor in favor of the parse function. All changes are backward-compatible. Full release notes.

    v2.0.2 (2016-07-31)

    Overhauls the parser (now rejecting unescaped control characters), tightens the class invariants, and cleans up the code. All changes are backward-compatible. Full release notes.

    v2.0.1 (2016-06-28)

    Fixes a performance regression in the dump function by adjusting the stream locale once per serialization. All changes are backward-compatible. Full release notes.

    v2.0.0 (2016-06-24)

    Feature release with a minor (potentially non-backward-compatible) API change from added noexcept and constexpr specifiers.

    Full release notes.

    v1.1.0 (2016-01-24)

    Bug-fix and feature release. All changes are backward-compatible.

    • Improves floating-point round-tripping, adds a get_ref accessor for stored values, and introduces runtime assertions.

    Full release notes.

    v1.0.0 (2015-12-28)

    First official release. Full release notes.

    See also

    • Migration Guide — how to future-proof your code for the next major version and replace deprecated functions.
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/home/sponsors/index.html b/home/sponsors/index.html index 59a5766cb..66aadef11 100644 --- a/home/sponsors/index.html +++ b/home/sponsors/index.html @@ -1 +1 @@ - Sponsors - JSON for Modern C++
    Skip to content
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + Sponsors - JSON for Modern C++
    Skip to content
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/index.html b/index.html index 893ff45cf..8969d9f65 100644 --- a/index.html +++ b/index.html @@ -1 +1 @@ - JSON for Modern C++ - JSON for Modern C++
    Skip to content

    JSON for Modern C++

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file + JSON for Modern C++ - JSON for Modern C++
    Skip to content

    JSON for Modern C++

    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file diff --git a/integration/cmake/index.html b/integration/cmake/index.html index f3ed92bc8..0c6520cbd 100644 --- a/integration/cmake/index.html +++ b/integration/cmake/index.html @@ -46,4 +46,4 @@ GIT_REPOSITORY https://github.com/nlohmann/json GIT_TAG v3.12.0 ) -

    However, the repository https://github.com/nlohmann/json download size is quite large.

    CMake Options

    JSON_BuildTests

    Build the unit tests when BUILD_TESTING is enabled. This option is ON by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.

    JSON_CI

    Enable CI build targets. The exact targets are used during the several CI steps and are subject to change without notice. This option is OFF by default.

    JSON_Diagnostics

    Enable extended diagnostic messages by defining macro JSON_DIAGNOSTICS. This option is OFF by default.

    JSON_Diagnostic_Positions

    Enable position diagnostics by defining macro JSON_DIAGNOSTIC_POSITIONS. This option is OFF by default.

    JSON_DisableEnumSerialization

    Disable default enum serialization by defining the macro JSON_DISABLE_ENUM_SERIALIZATION. This option is OFF by default.

    JSON_FastTests

    Skip expensive/slow test suites. This option is OFF by default. Depends on JSON_BuildTests.

    JSON_GlobalUDLs

    Place user-defined string literals in the global namespace by defining the macro JSON_USE_GLOBAL_UDLS. This option is OFF by default.

    JSON_ImplicitConversions

    Enable implicit conversions by defining macro JSON_USE_IMPLICIT_CONVERSIONS. This option is ON by default.

    JSON_Install

    Install CMake targets during install step. This option is ON by default if the library's CMake project is the top project.

    JSON_LegacyDiscardedValueComparison

    Enable the (incorrect) legacy comparison behavior of discarded JSON values by defining macro JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON. This option is OFF by default.

    JSON_MultipleHeaders

    Use the non-amalgamated version of the library. This option is ON by default.

    JSON_SystemInclude

    Treat the library headers like system headers (i.e., adding SYSTEM to the target_include_directories call) to check for this library by tools like Clang-Tidy. This option is OFF by default.

    JSON_Valgrind

    Execute the test suite with Valgrind. This option is OFF by default. Depends on JSON_BuildTests.

    NLOHMANN_JSON_BUILD_MODULES

    Build the experimental C++ module nlohmann.json (requires CMake 3.28 or later and C++20). This option is OFF by default.

    \ No newline at end of file +

    However, the repository https://github.com/nlohmann/json download size is quite large.

    CMake Options

    JSON_BuildTests

    Build the unit tests when BUILD_TESTING is enabled. This option is ON by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.

    JSON_CI

    Enable CI build targets. The exact targets are used during the several CI steps and are subject to change without notice. This option is OFF by default.

    JSON_Diagnostics

    Enable extended diagnostic messages by defining macro JSON_DIAGNOSTICS. This option is OFF by default.

    JSON_Diagnostic_Positions

    Enable position diagnostics by defining macro JSON_DIAGNOSTIC_POSITIONS. This option is OFF by default.

    JSON_DisableEnumSerialization

    Disable default enum serialization by defining the macro JSON_DISABLE_ENUM_SERIALIZATION. This option is OFF by default.

    JSON_FastTests

    Skip expensive/slow test suites. This option is OFF by default. Depends on JSON_BuildTests.

    JSON_GlobalUDLs

    Place user-defined string literals in the global namespace by defining the macro JSON_USE_GLOBAL_UDLS. This option is OFF by default.

    JSON_ImplicitConversions

    Enable implicit conversions by defining macro JSON_USE_IMPLICIT_CONVERSIONS. This option is ON by default.

    JSON_Install

    Install CMake targets during install step. This option is ON by default if the library's CMake project is the top project.

    JSON_LegacyDiscardedValueComparison

    Enable the (incorrect) legacy comparison behavior of discarded JSON values by defining macro JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON. This option is OFF by default.

    JSON_MultipleHeaders

    Use the non-amalgamated version of the library. This option is ON by default.

    JSON_SystemInclude

    Treat the library headers like system headers (i.e., adding SYSTEM to the target_include_directories call) to check for this library by tools like Clang-Tidy. This option is OFF by default.

    JSON_Valgrind

    Execute the test suite with Valgrind. This option is OFF by default. Depends on JSON_BuildTests.

    NLOHMANN_JSON_BUILD_MODULES

    Build the experimental C++ module nlohmann.json (requires CMake 3.28 or later and C++20). This option is OFF by default.

    \ No newline at end of file diff --git a/integration/index.html b/integration/index.html index d826f12da..a10b54f75 100644 --- a/integration/index.html +++ b/integration/index.html @@ -2,4 +2,4 @@ // for convenience using json = nlohmann::json; -

    to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., -std=c++11 for GCC and Clang).

    You can further use file single_include/nlohmann/json_fwd.hpp for forward declarations.

    \ No newline at end of file +

    to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., -std=c++11 for GCC and Clang).

    You can further use file single_include/nlohmann/json_fwd.hpp for forward declarations.

    \ No newline at end of file diff --git a/integration/migration_guide/index.html b/integration/migration_guide/index.html index be54512e7..fa9d15ca5 100644 --- a/integration/migration_guide/index.html +++ b/integration/migration_guide/index.html @@ -54,4 +54,4 @@ { j["age"] = p.age; } -

    Do not use the details namespace

    The details namespace is not part of the public API of the library and can change in any version without an announcement. Do not rely on any function or type in the details namespace.

    \ No newline at end of file +

    Do not use the details namespace

    The details namespace is not part of the public API of the library and can change in any version without an announcement. Do not rely on any function or type in the details namespace.

    \ No newline at end of file diff --git a/integration/package_managers/index.html b/integration/package_managers/index.html index 167c98806..ea284978f 100644 --- a/integration/package_managers/index.html +++ b/integration/package_managers/index.html @@ -416,4 +416,4 @@ cmake --build build set_languages("cxx11")

  • Build

    xmake

  • Run

    xmake run
-

    • Other package managers

    The library is also contained in many other package repositories: Packaging status

    Package version overview

    Packaging status

    Buckaroo

    If you are using Buckaroo, you can install this library's module with buckaroo add github.com/buckaroo-pm/nlohmann-json. There is a demo repo here.

    Warning

    The module is outdated as the respective repository has not been updated in years.

    CocoaPods

    If you are using CocoaPods, you can use the library by adding pod "nlohmann_json", '~>3.1.2' to your podfile (see an example). Please file issues here.

    Warning

    The module is outdated as the respective pod has not been updated in years.

    \ No newline at end of file +

    Other package managers

    The library is also contained in many other package repositories: Packaging status

    Package version overview

    Packaging status

    Buckaroo

    If you are using Buckaroo, you can install this library's module with buckaroo add github.com/buckaroo-pm/nlohmann-json. There is a demo repo here.

    Warning

    The module is outdated as the respective repository has not been updated in years.

    CocoaPods

    If you are using CocoaPods, you can use the library by adding pod "nlohmann_json", '~>3.1.2' to your podfile (see an example). Please file issues here.

    Warning

    The module is outdated as the respective pod has not been updated in years.

    \ No newline at end of file diff --git a/integration/pkg-config/index.html b/integration/pkg-config/index.html index 741f66ba6..ee054a44f 100644 --- a/integration/pkg-config/index.html +++ b/integration/pkg-config/index.html @@ -1,3 +1,3 @@ Pkg-config - JSON for Modern C++
    Skip to content

    Pkg-config

    If you are using bare Makefiles, you can use pkg-config to generate the include flags that point to where the library is installed:

    pkg-config nlohmann_json --cflags

    Users of the Meson build system will also be able to use a system-wide library, which will be found by pkg-config:

    json = dependency('nlohmann_json', required: true)
-
    Copyright © 2013-2026 Niels Lohmann
    \ No newline at end of file +
    \ No newline at end of file diff --git a/search/search_index.json b/search/search_index.json index e685e848b..864b6af9f 100644 --- a/search/search_index.json +++ b/search/search_index.json @@ -1 +1 @@ -{"config":{"lang":["en"],"separator":"[\\s\\-\\.]","pipeline":["stopWordFilter"],"fields":{"title":{"boost":1000.0},"text":{"boost":1.0},"tags":{"boost":1000000.0}}},"docs":[{"location":"","title":"JSON for Modern C++","text":""},{"location":"api/json/","title":"nlohmann::json","text":"
    using json = basic_json<>;\n

    This type is the default specialization of the basic_json class which uses the standard template types.

    "},{"location":"api/json/#examples","title":"Examples","text":"Example

    The example below demonstrates how to use the type nlohmann::json.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j =\n    {\n        {\"pi\", 3.141},\n        {\"happy\", true},\n        {\"name\", \"Niels\"},\n        {\"nothing\", nullptr},\n        {\n            \"answer\", {\n                {\"everything\", 42}\n            }\n        },\n        {\"list\", {1, 0, 2}},\n        {\n            \"object\", {\n                {\"currency\", \"USD\"},\n                {\"value\", 42.99}\n            }\n        }\n    };\n\n    // add new values\n    j[\"new\"][\"key\"][\"value\"] = {\"another\", \"list\"};\n\n    // count elements\n    auto s = j.size();\n    j[\"size\"] = s;\n\n    // pretty print with indent of 4 spaces\n    std::cout << std::setw(4) << j << '\\n';\n}\n

    Output:

    {\n    \"answer\": {\n        \"everything\": 42\n    },\n    \"happy\": true,\n    \"list\": [\n        1,\n        0,\n        2\n    ],\n    \"name\": \"Niels\",\n    \"new\": {\n        \"key\": {\n            \"value\": [\n                \"another\",\n                \"list\"\n            ]\n        }\n    },\n    \"nothing\": null,\n    \"object\": {\n        \"currency\": \"USD\",\n        \"value\": 42.99\n    },\n    \"pi\": 3.141,\n    \"size\": 8\n}\n
    "},{"location":"api/json/#version-history","title":"Version history","text":"

    Since version 1.0.0.

    "},{"location":"api/operator_gtgt/","title":"nlohmann::operator>>(basic_json)","text":"
    std::istream& operator>>(std::istream& i, basic_json& j);\n

    Deserializes an input stream to a JSON value.

    "},{"location":"api/operator_gtgt/#parameters","title":"Parameters","text":"i (in, out) input stream to read a serialized JSON value from j (in, out) JSON value to write the deserialized input to"},{"location":"api/operator_gtgt/#return-value","title":"Return value","text":"

    the stream i

    "},{"location":"api/operator_gtgt/#exceptions","title":"Exceptions","text":""},{"location":"api/operator_gtgt/#complexity","title":"Complexity","text":"

    Linear in the length of the input. The parser is a predictive LL(1) parser.

    "},{"location":"api/operator_gtgt/#notes","title":"Notes","text":"

    A UTF-8 byte order mark is silently ignored.

    Invalid Unicode escapes and unpaired surrogates in the input are reported as parse_error.101 with a detailed message.

    Deprecation

    This function replaces function std::istream& operator<<(basic_json& j, std::istream& i) which has been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like j << i; with i >> j;.

    "},{"location":"api/operator_gtgt/#examples","title":"Examples","text":"Example

    The example below shows how a JSON value is constructed by reading a serialization from a stream.

    #include <iostream>\n#include <iomanip>\n#include <sstream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create stream with serialized JSON\n    std::stringstream ss;\n    ss << R\"({\n        \"number\": 23,\n        \"string\": \"Hello, world!\",\n        \"array\": [1, 2, 3, 4, 5],\n        \"boolean\": false,\n        \"null\": null\n    })\";\n\n    // create JSON value and read the serialization from the stream\n    json j;\n    ss >> j;\n\n    // serialize JSON\n    std::cout << std::setw(2) << j << '\\n';\n}\n

    Output:

    {\n  \"array\": [\n    1,\n    2,\n    3,\n    4,\n    5\n  ],\n  \"boolean\": false,\n  \"null\": null,\n  \"number\": 23,\n  \"string\": \"Hello, world!\"\n}\n
    "},{"location":"api/operator_gtgt/#see-also","title":"See also","text":""},{"location":"api/operator_gtgt/#version-history","title":"Version history","text":""},{"location":"api/operator_literal_json/","title":"nlohmann::operator\"\"_json","text":"
    json operator \"\"_json(const char* s, std::size_t n);\njson operator \"\"_json(const char8_t* s, std::size_t n);  // since C++20\n

    This operator implements a user-defined string literal for JSON objects. It can be used by adding _json to a string literal and returns a json object if no parse error occurred.

    It is recommended to bring the operator into scope using any of the following lines: 

    using nlohmann::literals::operator \"\"_json;\nusing namespace nlohmann::literals;\nusing namespace nlohmann::json_literals;\nusing namespace nlohmann::literals::json_literals;\nusing namespace nlohmann;\n

    This is suggested to ease migration to the next major version release of the library. See JSON_USE_GLOBAL_UDLS for details.

    "},{"location":"api/operator_literal_json/#parameters","title":"Parameters","text":"s (in) a string representation of a JSON object n (in) length of string s"},{"location":"api/operator_literal_json/#return-value","title":"Return value","text":"

    json value parsed from s

    "},{"location":"api/operator_literal_json/#exceptions","title":"Exceptions","text":"

    The function can throw anything that parse(s, s+n) would throw.

    "},{"location":"api/operator_literal_json/#complexity","title":"Complexity","text":"

    Linear.

    "},{"location":"api/operator_literal_json/#examples","title":"Examples","text":"Example

    The following code shows how to create JSON values from string literals.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    json j = R\"( {\"hello\": \"world\", \"answer\": 42} )\"_json;\n\n    std::cout << std::setw(2) << j << '\\n';\n}\n

    Output:

    {\n  \"answer\": 42,\n  \"hello\": \"world\"\n}\n
    "},{"location":"api/operator_literal_json/#see-also","title":"See also","text":""},{"location":"api/operator_literal_json/#version-history","title":"Version history","text":""},{"location":"api/operator_literal_json_pointer/","title":"nlohmann::operator\"\"_json_pointer","text":"
    json_pointer operator \"\"_json_pointer(const char* s, std::size_t n);\njson_pointer operator \"\"_json_pointer(const char8_t* s, std::size_t n);  // since C++20\n

    This operator implements a user-defined string literal for JSON Pointers. It can be used by adding _json_pointer to a string literal and returns a json_pointer object if no parse error occurred.

    It is recommended to bring the operator into scope using any of the following lines: 

    using nlohmann::literals::operator \"\"_json_pointer;\nusing namespace nlohmann::literals;\nusing namespace nlohmann::json_literals;\nusing namespace nlohmann::literals::json_literals;\nusing namespace nlohmann;\n
    This is suggested to ease migration to the next major version release of the library. See JSON_USE_GLOBAL_UDLS for details.

    "},{"location":"api/operator_literal_json_pointer/#parameters","title":"Parameters","text":"s (in) a string representation of a JSON Pointer n (in) length of string s"},{"location":"api/operator_literal_json_pointer/#return-value","title":"Return value","text":"

    json_pointer value parsed from s

    "},{"location":"api/operator_literal_json_pointer/#exceptions","title":"Exceptions","text":"

    The function can throw anything that json_pointer::json_pointer would throw.

    "},{"location":"api/operator_literal_json_pointer/#complexity","title":"Complexity","text":"

    Linear.

    "},{"location":"api/operator_literal_json_pointer/#examples","title":"Examples","text":"Example

    The following code shows how to create JSON Pointers from string literals.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    json j = R\"( {\"hello\": \"world\", \"answer\": 42} )\"_json;\n    auto val = j[\"/hello\"_json_pointer];\n\n    std::cout << std::setw(2) << val << '\\n';\n}\n

    Output:

    \"world\"\n
    "},{"location":"api/operator_literal_json_pointer/#see-also","title":"See also","text":""},{"location":"api/operator_literal_json_pointer/#version-history","title":"Version history","text":""},{"location":"api/operator_ltlt/","title":"nlohmann::operator<<(basic_json), nlohmann::operator<<(json_pointer)","text":"
    std::ostream& operator<<(std::ostream& o, const basic_json& j);      // (1)\n\nstd::ostream& operator<<(std::ostream& o, const json_pointer& ptr);  // (2)\n
    1. Serialize the given JSON value j to the output stream o. The JSON value will be serialized using the dump member function.
      • The indentation of the output can be controlled with the member variable width of the output stream o. For instance, using the manipulator std::setw(4) on o sets the indentation level to 4 and the serialization result is the same as calling dump(4).
      • The indentation character can be controlled with the member variable fill of the output stream o. For instance, the manipulator std::setfill('\\\\t') sets indentation to use a tab character rather than the default space character.
    2. Write a string representation of the given JSON pointer ptr to the output stream o. The string representation is obtained using the to_string member function.
    "},{"location":"api/operator_ltlt/#parameters","title":"Parameters","text":"o (in, out) stream to write to j (in) JSON value to serialize ptr (in) JSON pointer to write"},{"location":"api/operator_ltlt/#return-value","title":"Return value","text":"

    the stream o

    "},{"location":"api/operator_ltlt/#exceptions","title":"Exceptions","text":"
    1. Throws type_error.316 if a string stored inside the JSON value is not UTF-8 encoded. Note that unlike the dump member functions, no error_handler can be set.
    2. None.
    "},{"location":"api/operator_ltlt/#complexity","title":"Complexity","text":"

    Linear.

    "},{"location":"api/operator_ltlt/#notes","title":"Notes","text":"

    Deprecation

    Function std::ostream& operator<<(std::ostream& o, const basic_json& j) replaces function std::ostream& operator>>(const basic_json& j, std::ostream& o) which has been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like j >> o; with o << j;.

    "},{"location":"api/operator_ltlt/#examples","title":"Examples","text":"Example: (1) serialize JSON value to stream

    The example below shows the serialization with different parameters to width to adjust the indentation level.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_array = {1, 2, 4, 8, 16};\n\n    // serialize without indentation\n    std::cout << j_object << \"\\n\\n\";\n    std::cout << j_array << \"\\n\\n\";\n\n    // serialize with indentation\n    std::cout << std::setw(4) << j_object << \"\\n\\n\";\n    std::cout << std::setw(2) << j_array << \"\\n\\n\";\n    std::cout << std::setw(1) << std::setfill('\\t') << j_object << \"\\n\\n\";\n}\n

    Output:

    {\"one\":1,\"two\":2}\n\n[1,2,4,8,16]\n\n{\n    \"one\": 1,\n    \"two\": 2\n}\n\n[\n  1,\n  2,\n  4,\n  8,\n  16\n]\n\n{\n    \"one\": 1,\n    \"two\": 2\n}\n
    Example: (2) write JSON pointer to stream

    The example below shows how to write a JSON pointer to a stream.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON pointer\n    json::json_pointer ptr(\"/foo/bar/baz\");\n\n    // write string representation to stream\n    std::cout << ptr << std::endl;\n}\n

    Output:

    /foo/bar/baz\n
    "},{"location":"api/operator_ltlt/#see-also","title":"See also","text":""},{"location":"api/operator_ltlt/#version-history","title":"Version history","text":"
    1. Added in version 1.0.0. Added support for indentation character and deprecated std::ostream& operator>>(const basic_json& j, std::ostream& o) in version 3.0.0.
    2. Added in version 3.11.0.
    "},{"location":"api/ordered_json/","title":"nlohmann::ordered_json","text":"
    using ordered_json = basic_json<ordered_map>;\n

    This type preserves the insertion order of object keys.

    "},{"location":"api/ordered_json/#iterator-invalidation","title":"Iterator invalidation","text":"

    The type is based on ordered_map which in turn uses a std::vector to store object elements. Therefore, adding object elements can yield a reallocation in which case all iterators (including the end() iterator) and all references to the elements are invalidated. Also, any iterator or reference after the insertion point will point to the same index, which is now a different value.

    "},{"location":"api/ordered_json/#examples","title":"Examples","text":"Example

    The example below demonstrates how ordered_json preserves the insertion order of object keys.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing ordered_json = nlohmann::ordered_json;\n\nint main()\n{\n    ordered_json j;\n    j[\"one\"] = 1;\n    j[\"two\"] = 2;\n    j[\"three\"] = 3;\n\n    std::cout << j.dump(2) << '\\n';\n}\n

    Output:

    {\n  \"one\": 1,\n  \"two\": 2,\n  \"three\": 3\n}\n
    "},{"location":"api/ordered_json/#see-also","title":"See also","text":""},{"location":"api/ordered_json/#version-history","title":"Version history","text":"

    Since version 3.9.0.

    "},{"location":"api/ordered_map/","title":"nlohmann::ordered_map","text":"
    template<class Key, class T, class IgnoredLess = std::less<Key>,\n         class Allocator = std::allocator<std::pair<const Key, T>>>\nstruct ordered_map : std::vector<std::pair<const Key, T>, Allocator>;\n

    A minimal map-like container that preserves insertion order for use within nlohmann::ordered_json (nlohmann::basic_json<ordered_map>).

    "},{"location":"api/ordered_map/#template-parameters","title":"Template parameters","text":"Key key type T mapped type IgnoredLess comparison function (ignored and only added to ensure compatibility with std::map) Allocator allocator type"},{"location":"api/ordered_map/#iterator-invalidation","title":"Iterator invalidation","text":"

    The type uses a std::vector to store object elements. Therefore, adding elements can yield a reallocation in which case all iterators (including the end() iterator) and all references to the elements are invalidated.

    "},{"location":"api/ordered_map/#member-types","title":"Member types","text":""},{"location":"api/ordered_map/#member-functions","title":"Member functions","text":""},{"location":"api/ordered_map/#examples","title":"Examples","text":"Example

    The example shows the different behavior of std::map and nlohmann::ordered_map.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\n// simple output function\ntemplate<typename Map>\nvoid output(const char* prefix, const Map& m)\n{\n    std::cout << prefix << \" = { \";\n    for (auto& element : m)\n    {\n        std::cout << element.first << \":\" << element.second << ' ';\n    }\n    std::cout << \"}\" << std::endl;\n}\n\nint main()\n{\n    // create and fill two maps\n    nlohmann::ordered_map<std::string, std::string> m_ordered;\n    m_ordered[\"one\"] = \"eins\";\n    m_ordered[\"two\"] = \"zwei\";\n    m_ordered[\"three\"] = \"drei\";\n\n    std::map<std::string, std::string> m_std;\n    m_std[\"one\"] = \"eins\";\n    m_std[\"two\"] = \"zwei\";\n    m_std[\"three\"] = \"drei\";\n\n    // output: m_ordered is ordered by insertion order, m_std is ordered by key\n    output(\"m_ordered\", m_ordered);\n    output(\"m_std\", m_std);\n\n    // erase and re-add \"one\" key\n    m_ordered.erase(\"one\");\n    m_ordered[\"one\"] = \"eins\";\n\n    m_std.erase(\"one\");\n    m_std[\"one\"] = \"eins\";\n\n    // output: m_ordered shows newly added key at the end; m_std is again ordered by key\n    output(\"m_ordered\", m_ordered);\n    output(\"m_std\", m_std);\n}\n

    Output:

    m_ordered = { one:eins two:zwei three:drei }\nm_std = { one:eins three:drei two:zwei }\nm_ordered = { two:zwei three:drei one:eins }\nm_std = { one:eins three:drei two:zwei }\n
    "},{"location":"api/ordered_map/#see-also","title":"See also","text":""},{"location":"api/ordered_map/#version-history","title":"Version history","text":""},{"location":"api/adl_serializer/","title":"nlohmann::adl_serializer","text":"
    template<typename, typename>\nstruct adl_serializer;\n

    Serializer that uses ADL (Argument-Dependent Lookup) to choose to_json/from_json functions from the types' namespaces.

    It is implemented similarly to

    template<typename ValueType>\nstruct adl_serializer {\n    template<typename BasicJsonType>\n    static void to_json(BasicJsonType& j, const T& value) {\n        // calls the \"to_json\" method in T's namespace\n    }\n\n    template<typename BasicJsonType>\n    static void from_json(const BasicJsonType& j, T& value) {\n        // same thing, but with the \"from_json\" method\n    }\n};\n
    "},{"location":"api/adl_serializer/#member-functions","title":"Member functions","text":""},{"location":"api/adl_serializer/#version-history","title":"Version history","text":""},{"location":"api/adl_serializer/from_json/","title":"nlohmann::adl_serializer::from_json","text":"
    // (1)\ntemplate<typename BasicJsonType, typename TargetType = ValueType>\nstatic auto from_json(BasicJsonType && j, TargetType& val) noexcept(\n    noexcept(::nlohmann::from_json(std::forward<BasicJsonType>(j), val)))\n-> decltype(::nlohmann::from_json(std::forward<BasicJsonType>(j), val), void())\n\n// (2)\ntemplate<typename BasicJsonType, typename TargetType = ValueType>\nstatic auto from_json(BasicJsonType && j) noexcept(\nnoexcept(::nlohmann::from_json(std::forward<BasicJsonType>(j), detail::identity_tag<TargetType> {})))\n-> decltype(::nlohmann::from_json(std::forward<BasicJsonType>(j), detail::identity_tag<TargetType> {}))\n

    This function is usually called by the get() function of the basic_json class (either explicitly or via the conversion operators).

    1. This function is chosen for default-constructible value types.
    2. This function is chosen for value types which are not default-constructible.
    "},{"location":"api/adl_serializer/from_json/#parameters","title":"Parameters","text":"j (in) JSON value to read from val (out) value to write to"},{"location":"api/adl_serializer/from_json/#return-value","title":"Return value","text":"
    1. (none) -- the converted value is written to the output parameter val.
    2. the JSON value j converted to TargetType
    "},{"location":"api/adl_serializer/from_json/#examples","title":"Examples","text":"Example: (1) Default-constructible type

    The example below shows how a from_json function can be implemented for a user-defined type. This function is called by the adl_serializer when get<ns::person>() is called.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nnamespace ns\n{\n// a simple struct to model a person\nstruct person\n{\n    std::string name;\n    std::string address;\n    int age;\n};\n} // namespace ns\n\nnamespace ns\n{\nvoid from_json(const json& j, person& p)\n{\n    j.at(\"name\").get_to(p.name);\n    j.at(\"address\").get_to(p.address);\n    j.at(\"age\").get_to(p.age);\n}\n} // namespace ns\n\nint main()\n{\n    json j;\n    j[\"name\"] = \"Ned Flanders\";\n    j[\"address\"] = \"744 Evergreen Terrace\";\n    j[\"age\"] = 60;\n\n    auto p = j.get<ns::person>();\n\n    std::cout << p.name << \" (\" << p.age << \") lives in \" << p.address << std::endl;\n}\n

    Output:

    Ned Flanders (60) lives in 744 Evergreen Terrace\n
    Example: (2) Non-default-constructible type

    The example below shows how a from_json is implemented as part of a specialization of the adl_serializer to realize the conversion of a non-default-constructible type.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nnamespace ns\n{\n// a simple struct to model a person (not default constructible)\nstruct person\n{\n    person(std::string n, std::string a, int aa)\n        : name(std::move(n)), address(std::move(a)), age(aa)\n    {}\n\n    std::string name;\n    std::string address;\n    int age;\n};\n} // namespace ns\n\nnamespace nlohmann\n{\ntemplate <>\nstruct adl_serializer<ns::person>\n{\n    static ns::person from_json(const json& j)\n    {\n        return {j.at(\"name\"), j.at(\"address\"), j.at(\"age\")};\n    }\n\n    // Here's the catch! You must provide a to_json method! Otherwise, you\n    // will not be able to convert person to json, since you fully\n    // specialized adl_serializer on that type\n    static void to_json(json& j, ns::person p)\n    {\n        j[\"name\"] = p.name;\n        j[\"address\"] = p.address;\n        j[\"age\"] = p.age;\n    }\n};\n} // namespace nlohmann\n\nint main()\n{\n    json j;\n    j[\"name\"] = \"Ned Flanders\";\n    j[\"address\"] = \"744 Evergreen Terrace\";\n    j[\"age\"] = 60;\n\n    auto p = j.get<ns::person>();\n\n    std::cout << p.name << \" (\" << p.age << \") lives in \" << p.address << std::endl;\n}\n

    Output:

    Ned Flanders (60) lives in 744 Evergreen Terrace\n
    "},{"location":"api/adl_serializer/from_json/#see-also","title":"See also","text":""},{"location":"api/adl_serializer/from_json/#version-history","title":"Version history","text":""},{"location":"api/adl_serializer/to_json/","title":"nlohmann::adl_serializer::to_json","text":"
    template<typename BasicJsonType, typename TargetType = ValueType>\nstatic auto to_json(BasicJsonType& j, TargetType && val) noexcept(\n    noexcept(::nlohmann::to_json(j, std::forward<TargetType>(val))))\n-> decltype(::nlohmann::to_json(j, std::forward<TargetType>(val)), void())\n

    This function is usually called by the constructors of the basic_json class.

    "},{"location":"api/adl_serializer/to_json/#parameters","title":"Parameters","text":"j (out) JSON value to write to val (in) value to read from"},{"location":"api/adl_serializer/to_json/#examples","title":"Examples","text":"Example

    The example below shows how a to_json function can be implemented for a user-defined type. This function is called by the adl_serializer when the constructor basic_json(ns::person) is called.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nnamespace ns\n{\n// a simple struct to model a person\nstruct person\n{\n    std::string name;\n    std::string address;\n    int age;\n};\n} // namespace ns\n\nnamespace ns\n{\nvoid to_json(json& j, const person& p)\n{\n    j = json{ {\"name\", p.name}, {\"address\", p.address}, {\"age\", p.age} };\n}\n} // namespace ns\n\nint main()\n{\n    ns::person p = {\"Ned Flanders\", \"744 Evergreen Terrace\", 60};\n\n    json j = p;\n\n    std::cout << j << std::endl;\n}\n

    Output:

    {\"address\":\"744 Evergreen Terrace\",\"age\":60,\"name\":\"Ned Flanders\"}\n
    "},{"location":"api/adl_serializer/to_json/#see-also","title":"See also","text":""},{"location":"api/adl_serializer/to_json/#version-history","title":"Version history","text":""},{"location":"api/basic_json/","title":"nlohmann::basic_json","text":"

    Defined in header <nlohmann/json.hpp>

    template<\n    template<typename U, typename V, typename... Args> class ObjectType = std::map,\n    template<typename U, typename... Args> class ArrayType = std::vector,\n    class StringType = std::string,\n    class BooleanType = bool,\n    class NumberIntegerType = std::int64_t,\n    class NumberUnsignedType = std::uint64_t,\n    class NumberFloatType = double,\n    template<typename U> class AllocatorType = std::allocator,\n    template<typename T, typename SFINAE = void> class JSONSerializer = adl_serializer,\n    class BinaryType = std::vector<std::uint8_t>,\n    class CustomBaseClass = void\n>\nclass basic_json;\n
    "},{"location":"api/basic_json/#template-parameters","title":"Template parameters","text":"Template parameter Description Derived type ObjectType type for JSON objects object_t ArrayType type for JSON arrays array_t StringType type for JSON strings and object keys string_t BooleanType type for JSON booleans boolean_t NumberIntegerType type for JSON integer numbers number_integer_t NumberUnsignedType type for JSON unsigned integer numbers number_unsigned_t NumberFloatType type for JSON floating-point numbers number_float_t AllocatorType type of the allocator to use JSONSerializer the serializer to resolve internal calls to to_json() and from_json() json_serializer BinaryType type for binary arrays binary_t CustomBaseClass extension point for user code json_base_class_t"},{"location":"api/basic_json/#specializations","title":"Specializations","text":""},{"location":"api/basic_json/#iterator-invalidation","title":"Iterator invalidation","text":"

    All operations that add values to an array (push_back , operator+=, emplace_back, insert, and operator[] for a non-existing index) can yield a reallocation, in which case all iterators (including the end() iterator) and all references to the elements are invalidated.

    For ordered_json, also all operations that add a value to an object (push_back, operator+=, emplace, insert, update, and operator[] for a non-existing key) can yield a reallocation, in which case all iterators (including the end() iterator) and all references to the elements are invalidated.

    "},{"location":"api/basic_json/#requirements","title":"Requirements","text":"

    The class satisfies the following concept requirements:

    "},{"location":"api/basic_json/#basic","title":"Basic","text":""},{"location":"api/basic_json/#layout","title":"Layout","text":""},{"location":"api/basic_json/#library-wide","title":"Library-wide","text":""},{"location":"api/basic_json/#container","title":"Container","text":""},{"location":"api/basic_json/#member-types","title":"Member types","text":""},{"location":"api/basic_json/#exceptions","title":"Exceptions","text":""},{"location":"api/basic_json/#container-types","title":"Container types","text":"Type Definition value_type basic_json reference value_type& const_reference const value_type& difference_type std::ptrdiff_t size_type std::size_t allocator_type AllocatorType<basic_json> pointer std::allocator_traits<allocator_type>::pointer const_pointer std::allocator_traits<allocator_type>::const_pointer iterator LegacyBidirectionalIterator const_iterator constant LegacyBidirectionalIterator reverse_iterator reverse iterator, derived from iterator const_reverse_iterator reverse iterator, derived from const_iterator iteration_proxy helper type for items function"},{"location":"api/basic_json/#json-value-data-types","title":"JSON value data types","text":""},{"location":"api/basic_json/#parser-callback","title":"Parser callback","text":""},{"location":"api/basic_json/#member-functions","title":"Member functions","text":""},{"location":"api/basic_json/#object-inspection","title":"Object inspection","text":"

    Functions to inspect the type of a JSON value.

    Optional functions to access the diagnostic positions.

    "},{"location":"api/basic_json/#value-access","title":"Value access","text":"

    Direct access to the stored value of a JSON value.

    "},{"location":"api/basic_json/#element-access","title":"Element access","text":"

    Access to the JSON value

    "},{"location":"api/basic_json/#lookup","title":"Lookup","text":""},{"location":"api/basic_json/#iterators","title":"Iterators","text":""},{"location":"api/basic_json/#capacity","title":"Capacity","text":""},{"location":"api/basic_json/#modifiers","title":"Modifiers","text":""},{"location":"api/basic_json/#lexicographical-comparison-operators","title":"Lexicographical comparison operators","text":""},{"location":"api/basic_json/#serialization-dumping","title":"Serialization / Dumping","text":""},{"location":"api/basic_json/#deserialization-parsing","title":"Deserialization / Parsing","text":""},{"location":"api/basic_json/#json-pointer-functions","title":"JSON Pointer functions","text":""},{"location":"api/basic_json/#json-patch-functions","title":"JSON Patch functions","text":""},{"location":"api/basic_json/#json-merge-patch-functions","title":"JSON Merge Patch functions","text":""},{"location":"api/basic_json/#static-functions","title":"Static functions","text":""},{"location":"api/basic_json/#binary-formats","title":"Binary formats","text":""},{"location":"api/basic_json/#non-member-functions","title":"Non-member functions","text":""},{"location":"api/basic_json/#literals","title":"Literals","text":""},{"location":"api/basic_json/#helper-classes","title":"Helper classes","text":""},{"location":"api/basic_json/#examples","title":"Examples","text":"Example

    The example shows how the library is used.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j =\n    {\n        {\"pi\", 3.141},\n        {\"happy\", true},\n        {\"name\", \"Niels\"},\n        {\"nothing\", nullptr},\n        {\n            \"answer\", {\n                {\"everything\", 42}\n            }\n        },\n        {\"list\", {1, 0, 2}},\n        {\n            \"object\", {\n                {\"currency\", \"USD\"},\n                {\"value\", 42.99}\n            }\n        }\n    };\n\n    // add new values\n    j[\"new\"][\"key\"][\"value\"] = {\"another\", \"list\"};\n\n    // count elements\n    auto s = j.size();\n    j[\"size\"] = s;\n\n    // pretty print with indent of 4 spaces\n    std::cout << std::setw(4) << j << '\\n';\n}\n

    Output:

    {\n    \"answer\": {\n        \"everything\": 42\n    },\n    \"happy\": true,\n    \"list\": [\n        1,\n        0,\n        2\n    ],\n    \"name\": \"Niels\",\n    \"new\": {\n        \"key\": {\n            \"value\": [\n                \"another\",\n                \"list\"\n            ]\n        }\n    },\n    \"nothing\": null,\n    \"object\": {\n        \"currency\": \"USD\",\n        \"value\": 42.99\n    },\n    \"pi\": 3.141,\n    \"size\": 8\n}\n
    "},{"location":"api/basic_json/#see-also","title":"See also","text":""},{"location":"api/basic_json/#version-history","title":"Version history","text":""},{"location":"api/basic_json/accept/","title":"nlohmann::basic_json::accept","text":"
    // (1)\ntemplate<typename InputType>\nstatic bool accept(InputType&& i,\n                   const bool ignore_comments = false,\n                   const bool ignore_trailing_commas = false);\n\n// (2)\ntemplate<typename IteratorType>\nstatic bool accept(IteratorType first, IteratorType last,\n                   const bool ignore_comments = false,\n                   const bool ignore_trailing_commas = false);\n

    Checks whether the input is valid JSON.

    1. Reads from a compatible input.

    2. Reads from a pair of character iterators

      The value_type of the iterator must be an integral type with a size of 1, 2, or 4 bytes, which will be interpreted respectively as UTF-8, UTF-16, and UTF-32.

    Unlike the parse() function, this function neither throws an exception in case of invalid JSON input (i.e., a parse error) nor creates diagnostic information.

    "},{"location":"api/basic_json/accept/#template-parameters","title":"Template parameters","text":"InputType

    A compatible input, for instance:

    IteratorType

    a compatible iterator type, for instance.

    "},{"location":"api/basic_json/accept/#parameters","title":"Parameters","text":"i (in) Input to parse from. ignore_comments (in) whether comments should be ignored and treated like whitespace (true) or yield a parse error (false); (optional, false by default) ignore_trailing_commas (in) whether trailing commas in arrays or objects should be ignored and treated like whitespace (true) or yield a parse error (false); (optional, false by default) first (in) iterator to the start of the character range last (in) iterator to the end of the character range"},{"location":"api/basic_json/accept/#return-value","title":"Return value","text":"

    Whether the input is valid JSON.

    "},{"location":"api/basic_json/accept/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

    "},{"location":"api/basic_json/accept/#exceptions","title":"Exceptions","text":"

    Throws parse_error.101 in case of an empty input like a null FILE* or char* pointer.

    "},{"location":"api/basic_json/accept/#complexity","title":"Complexity","text":"

    Linear in the length of the input. The parser is a predictive LL(1) parser.

    "},{"location":"api/basic_json/accept/#notes","title":"Notes","text":"

    A UTF-8 byte order mark is silently ignored.

    "},{"location":"api/basic_json/accept/#examples","title":"Examples","text":"Example

    The example below demonstrates the accept() function reading from a string.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // a valid JSON text\n    auto valid_text = R\"(\n    {\n        \"numbers\": [1, 2, 3]\n    }\n    )\";\n\n    // an invalid JSON text\n    auto invalid_text = R\"(\n    {\n        \"strings\": [\"extra\", \"comma\", ]\n    }\n    )\";\n\n    std::cout << std::boolalpha\n              << json::accept(valid_text) << ' '\n              << json::accept(invalid_text) << '\\n';\n}\n

    Output:

    true false\n
    "},{"location":"api/basic_json/accept/#see-also","title":"See also","text":""},{"location":"api/basic_json/accept/#version-history","title":"Version history","text":"

    Deprecation

    Overload (2) replaces calls to accept with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like accept({ptr, ptr+len}, ...); with accept(ptr, ptr+len, ...);.

    You should be warned by your compiler with a -Wdeprecated-declarations warning if you are using a deprecated function.

    "},{"location":"api/basic_json/array/","title":"nlohmann::basic_json::array","text":"
    static basic_json array(initializer_list_t init = {});\n

    Creates a JSON array value from a given initializer list. That is, given a list of values a, b, c, creates the JSON value [a, b, c]. If the initializer list is empty, the empty array [] is created.

    "},{"location":"api/basic_json/array/#parameters","title":"Parameters","text":"init (in) initializer list with JSON values to create an array from (optional)"},{"location":"api/basic_json/array/#return-value","title":"Return value","text":"

    JSON array value

    "},{"location":"api/basic_json/array/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

    "},{"location":"api/basic_json/array/#complexity","title":"Complexity","text":"

    Linear in the size of init.

    "},{"location":"api/basic_json/array/#notes","title":"Notes","text":"

    This function is only needed to express two edge cases that cannot be realized with the initializer list constructor (basic_json(initializer_list_t, bool, value_t)). These cases are:

    1. creating an array whose elements are all pairs whose first element is a string -- in this case, the initializer list constructor would create an object, taking the first elements as keys
    2. creating an empty array -- passing the empty initializer list to the initializer list constructor yields an empty object
    "},{"location":"api/basic_json/array/#examples","title":"Examples","text":"Example

    The following code shows an example for the array function.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON arrays\n    json j_no_init_list = json::array();\n    json j_empty_init_list = json::array({});\n    json j_nonempty_init_list = json::array({1, 2, 3, 4});\n    json j_list_of_pairs = json::array({ {\"one\", 1}, {\"two\", 2} });\n\n    // serialize the JSON arrays\n    std::cout << j_no_init_list << '\\n';\n    std::cout << j_empty_init_list << '\\n';\n    std::cout << j_nonempty_init_list << '\\n';\n    std::cout << j_list_of_pairs << '\\n';\n}\n

    Output:

    []\n[]\n[1,2,3,4]\n[[\"one\",1],[\"two\",2]]\n
    "},{"location":"api/basic_json/array/#see-also","title":"See also","text":""},{"location":"api/basic_json/array/#version-history","title":"Version history","text":""},{"location":"api/basic_json/array_t/","title":"nlohmann::basic_json::array_t","text":"
    using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;\n

    The type used to store JSON arrays.

    RFC 8259 describes JSON arrays as follows:

    An array is an ordered sequence of zero or more values.

    To store objects in C++, a type is defined by the template parameters explained below.

    "},{"location":"api/basic_json/array_t/#template-parameters","title":"Template parameters","text":"ArrayType container type to store arrays (e.g., std::vector or std::list) AllocatorType the allocator to use for objects (e.g., std::allocator)"},{"location":"api/basic_json/array_t/#notes","title":"Notes","text":""},{"location":"api/basic_json/array_t/#default-type","title":"Default type","text":"

    With the default values for ArrayType (std::vector) and AllocatorType (std::allocator), the default value for array_t is:

    std::vector<\n  basic_json, // value_type\n  std::allocator<basic_json> // allocator_type\n>\n
    "},{"location":"api/basic_json/array_t/#limits","title":"Limits","text":"

    RFC 8259 specifies:

    An implementation may set limits on the maximum depth of nesting.

    In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON array.

    "},{"location":"api/basic_json/array_t/#storage","title":"Storage","text":"

    Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of type array_t* must be dereferenced.

    "},{"location":"api/basic_json/array_t/#examples","title":"Examples","text":"Example

    The following code shows that array_t is by default, a typedef to std::vector<nlohmann::json>.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    std::cout << std::boolalpha << std::is_same<std::vector<json>, json::array_t>::value << std::endl;\n}\n

    Output:

    true\n
    "},{"location":"api/basic_json/array_t/#version-history","title":"Version history","text":""},{"location":"api/basic_json/at/","title":"nlohmann::basic_json::at","text":"
    // (1)\nreference at(size_type idx);\nconst_reference at(size_type idx) const;\n\n// (2)\nreference at(const typename object_t::key_type& key);\nconst_reference at(const typename object_t::key_type& key) const;\n\n// (3)\ntemplate<typename KeyType>\nreference at(KeyType&& key);\ntemplate<typename KeyType>\nconst_reference at(KeyType&& key) const;\n\n// (4)\nreference at(const json_pointer& ptr);\nconst_reference at(const json_pointer& ptr) const;\n
    1. Returns a reference to the array element at specified location idx, with bounds checking.
    2. Returns a reference to the object element with specified key key, with bounds checking.
    3. See 2. This overload is only available if KeyType is comparable with typename object_t::key_type and typename object_comparator_t::is_transparent denotes a type.
    4. Returns a reference to the element at specified JSON pointer ptr, with bounds checking.
    "},{"location":"api/basic_json/at/#template-parameters","title":"Template parameters","text":"KeyType A type for an object key other than json_pointer that is comparable with string_t using object_comparator_t. This can also be a string view (C++17)."},{"location":"api/basic_json/at/#parameters","title":"Parameters","text":"idx (in) index of the element to access key (in) object key of the elements to access ptr (in) JSON pointer to the desired element"},{"location":"api/basic_json/at/#return-value","title":"Return value","text":"
    1. reference to the element at index idx
    2. reference to the element at key key
    3. reference to the element at key key
    4. reference to the element pointed to by ptr
    "},{"location":"api/basic_json/at/#exception-safety","title":"Exception safety","text":"

    Strong exception safety: if an exception occurs, the original value stays intact.

    "},{"location":"api/basic_json/at/#exceptions","title":"Exceptions","text":"
    1. The function can throw the following exceptions:
      • Throws type_error.304 if the JSON value is not an array; in this case, calling at with an index makes no sense. See the example below.
      • Throws out_of_range.401 if the index idx is out of range of the array; that is, idx >= size(). See the example below.
    2. The function can throw the following exceptions:
      • Throws type_error.304 if the JSON value is not an object; in this case, calling at with a key makes no sense. See the example below.
      • Throws out_of_range.403 if the key key is not stored in the object; that is, find(key) == end(). See the example below.
    3. See 2.
    4. The function can throw the following exceptions:
      • Throws parse_error.106 if an array index in the passed JSON pointer ptr begins with '0'. See the example below.
      • Throws parse_error.109 if an array index in the passed JSON pointer ptr is not a number. See the example below.
      • Throws out_of_range.401 if an array index in the passed JSON pointer ptr is out of range. See the example below.
      • Throws out_of_range.402 if the array index '-' is used in the passed JSON pointer ptr. As at provides checked access (and no elements are implicitly inserted), the index '-' is always invalid. See the example below.
      • Throws out_of_range.403 if the JSON pointer describes a key of an object which cannot be found. See the example below.
      • Throws out_of_range.404 if the JSON pointer ptr can not be resolved. See the example below.
      • Throws out_of_range.410 if an array index in the passed JSON pointer ptr exceeds the range of size_type (e.g., on 32-bit platforms).
    "},{"location":"api/basic_json/at/#complexity","title":"Complexity","text":"
    1. Constant.
    2. Logarithmic in the size of the container.
    3. Logarithmic in the size of the container.
    4. Logarithmic in the size of the container.
    "},{"location":"api/basic_json/at/#examples","title":"Examples","text":"Example: (1) access specified array element with bounds checking

    The example below shows how array elements can be read and written using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON array\n    json array = {\"first\", \"2nd\", \"third\", \"fourth\"};\n\n    // output element at index 2 (third element)\n    std::cout << array.at(2) << '\\n';\n\n    // change element at index 1 (second element) to \"second\"\n    array.at(1) = \"second\";\n\n    // output changed array\n    std::cout << array << '\\n';\n\n    // exception type_error.304\n    try\n    {\n        // use at() on a non-array type\n        json str = \"I am a string\";\n        str.at(0) = \"Another string\";\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // exception out_of_range.401\n    try\n    {\n        // try to write beyond the array limit\n        array.at(5) = \"sixth\";\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    \"third\"\n[\"first\",\"second\",\"third\",\"fourth\"]\n[json.exception.type_error.304] cannot use at() with string\n[json.exception.out_of_range.401] array index 5 is out of range\n
    Example: (1) access specified array element with bounds checking

    The example below shows how array elements can be read using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON array\n    const json array = {\"first\", \"2nd\", \"third\", \"fourth\"};\n\n    // output element at index 2 (third element)\n    std::cout << array.at(2) << '\\n';\n\n    // exception type_error.304\n    try\n    {\n        // use at() on a non-array type\n        const json str = \"I am a string\";\n        std::cout << str.at(0) << '\\n';\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // exception out_of_range.401\n    try\n    {\n        // try to read beyond the array limit\n        std::cout << array.at(5) << '\\n';\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    \"third\"\n[json.exception.type_error.304] cannot use at() with string\n[json.exception.out_of_range.401] array index 5 is out of range\n
    Example: (2) access specified object element with bounds checking

    The example below shows how object elements can be read and written using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON object\n    json object =\n    {\n        {\"the good\", \"il buono\"},\n        {\"the bad\", \"il cattivo\"},\n        {\"the ugly\", \"il brutto\"}\n    };\n\n    // output element with key \"the ugly\"\n    std::cout << object.at(\"the ugly\") << '\\n';\n\n    // change element with key \"the bad\"\n    object.at(\"the bad\") = \"il cattivo\";\n\n    // output changed array\n    std::cout << object << '\\n';\n\n    // exception type_error.304\n    try\n    {\n        // use at() on a non-object type\n        json str = \"I am a string\";\n        str.at(\"the good\") = \"Another string\";\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // exception out_of_range.401\n    try\n    {\n        // try to write at a nonexisting key\n        object.at(\"the fast\") = \"il rapido\";\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    \"il brutto\"\n{\"the bad\":\"il cattivo\",\"the good\":\"il buono\",\"the ugly\":\"il brutto\"}\n[json.exception.type_error.304] cannot use at() with string\n[json.exception.out_of_range.403] key 'the fast' not found\n
    Example: (2) access specified object element with bounds checking

    The example below shows how object elements can be read using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON object\n    const json object =\n    {\n        {\"the good\", \"il buono\"},\n        {\"the bad\", \"il cattivo\"},\n        {\"the ugly\", \"il brutto\"}\n    };\n\n    // output element with key \"the ugly\"\n    std::cout << object.at(\"the ugly\") << '\\n';\n\n    // exception type_error.304\n    try\n    {\n        // use at() on a non-object type\n        const json str = \"I am a string\";\n        std::cout << str.at(\"the good\") << '\\n';\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // exception out_of_range.401\n    try\n    {\n        // try to read from a nonexisting key\n        std::cout << object.at(\"the fast\") << '\\n';\n    }\n    catch (const json::out_of_range)\n    {\n        std::cout << \"out of range\" << '\\n';\n    }\n}\n

    Output:

    \"il brutto\"\n[json.exception.type_error.304] cannot use at() with string\nout of range\n
    Example: (3) access specified object element using string_view with bounds checking

    The example below shows how object elements can be read and written using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <string_view>\n#include <nlohmann/json.hpp>\n\nusing namespace std::string_view_literals;\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON object\n    json object =\n    {\n        {\"the good\", \"il buono\"},\n        {\"the bad\", \"il cattivo\"},\n        {\"the ugly\", \"il brutto\"}\n    };\n\n    // output element with key \"the ugly\" using string_view\n    std::cout << object.at(\"the ugly\"sv) << '\\n';\n\n    // change element with key \"the bad\" using string_view\n    object.at(\"the bad\"sv) = \"il cattivo\";\n\n    // output changed array\n    std::cout << object << '\\n';\n\n    // exception type_error.304\n    try\n    {\n        // use at() with string_view on a non-object type\n        json str = \"I am a string\";\n        str.at(\"the good\"sv) = \"Another string\";\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // exception out_of_range.401\n    try\n    {\n        // try to write at a nonexisting key using string_view\n        object.at(\"the fast\"sv) = \"il rapido\";\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    \"il brutto\"\n{\"the bad\":\"il cattivo\",\"the good\":\"il buono\",\"the ugly\":\"il brutto\"}\n[json.exception.type_error.304] cannot use at() with string\n[json.exception.out_of_range.403] key 'the fast' not found\n
    Example: (3) access specified object element using string_view with bounds checking

    The example below shows how object elements can be read using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <string_view>\n#include <nlohmann/json.hpp>\n\nusing namespace std::string_view_literals;\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON object\n    const json object =\n    {\n        {\"the good\", \"il buono\"},\n        {\"the bad\", \"il cattivo\"},\n        {\"the ugly\", \"il brutto\"}\n    };\n\n    // output element with key \"the ugly\" using string_view\n    std::cout << object.at(\"the ugly\"sv) << '\\n';\n\n    // exception type_error.304\n    try\n    {\n        // use at() with string_view on a non-object type\n        const json str = \"I am a string\";\n        std::cout << str.at(\"the good\"sv) << '\\n';\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // exception out_of_range.401\n    try\n    {\n        // try to read from a nonexisting key using string_view\n        std::cout << object.at(\"the fast\"sv) << '\\n';\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << \"out of range\" << '\\n';\n    }\n}\n

    Output:

    \"il brutto\"\n[json.exception.type_error.304] cannot use at() with string\nout of range\n
    Example: (4) access specified element via JSON Pointer

    The example below shows how object elements can be read and written using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    // create a JSON value\n    json j =\n    {\n        {\"number\", 1}, {\"string\", \"foo\"}, {\"array\", {1, 2}}\n    };\n\n    // read-only access\n\n    // output element with JSON pointer \"/number\"\n    std::cout << j.at(\"/number\"_json_pointer) << '\\n';\n    // output element with JSON pointer \"/string\"\n    std::cout << j.at(\"/string\"_json_pointer) << '\\n';\n    // output element with JSON pointer \"/array\"\n    std::cout << j.at(\"/array\"_json_pointer) << '\\n';\n    // output element with JSON pointer \"/array/1\"\n    std::cout << j.at(\"/array/1\"_json_pointer) << '\\n';\n\n    // writing access\n\n    // change the string\n    j.at(\"/string\"_json_pointer) = \"bar\";\n    // output the changed string\n    std::cout << j[\"string\"] << '\\n';\n\n    // change an array element\n    j.at(\"/array/1\"_json_pointer) = 21;\n    // output the changed array\n    std::cout << j[\"array\"] << '\\n';\n\n    // out_of_range.106\n    try\n    {\n        // try to use an array index with leading '0'\n        json::reference ref = j.at(\"/array/01\"_json_pointer);\n    }\n    catch (const json::parse_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.109\n    try\n    {\n        // try to use an array index that is not a number\n        json::reference ref = j.at(\"/array/one\"_json_pointer);\n    }\n    catch (const json::parse_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.401\n    try\n    {\n        // try to use an invalid array index\n        json::reference ref = j.at(\"/array/4\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.402\n    try\n    {\n        // try to use the array index '-'\n        json::reference ref = j.at(\"/array/-\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.403\n    try\n    {\n        // try to use a JSON pointer to a nonexistent object key\n        json::const_reference ref = j.at(\"/foo\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.404\n    try\n    {\n        // try to use a JSON pointer that cannot be resolved\n        json::reference ref = j.at(\"/number/foo\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    1\n\"foo\"\n[1,2]\n2\n\"bar\"\n[1,21]\n[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'\n[json.exception.parse_error.109] parse error: array index 'one' is not a number\n[json.exception.out_of_range.401] array index 4 is out of range\n[json.exception.out_of_range.402] array index '-' (2) is out of range\n[json.exception.out_of_range.403] key 'foo' not found\n[json.exception.out_of_range.404] unresolved reference token 'foo'\n
    Example: (4) access specified element via JSON Pointer

    The example below shows how object elements can be read using at(). It also demonstrates the different exceptions that can be thrown.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    // create a JSON value\n    const json j =\n    {\n        {\"number\", 1}, {\"string\", \"foo\"}, {\"array\", {1, 2}}\n    };\n\n    // read-only access\n\n    // output element with JSON pointer \"/number\"\n    std::cout << j.at(\"/number\"_json_pointer) << '\\n';\n    // output element with JSON pointer \"/string\"\n    std::cout << j.at(\"/string\"_json_pointer) << '\\n';\n    // output element with JSON pointer \"/array\"\n    std::cout << j.at(\"/array\"_json_pointer) << '\\n';\n    // output element with JSON pointer \"/array/1\"\n    std::cout << j.at(\"/array/1\"_json_pointer) << '\\n';\n\n    // out_of_range.109\n    try\n    {\n        // try to use an array index that is not a number\n        json::const_reference ref = j.at(\"/array/one\"_json_pointer);\n    }\n    catch (const json::parse_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.401\n    try\n    {\n        // try to use an invalid array index\n        json::const_reference ref = j.at(\"/array/4\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.402\n    try\n    {\n        // try to use the array index '-'\n        json::const_reference ref = j.at(\"/array/-\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.403\n    try\n    {\n        // try to use a JSON pointer to a nonexistent object key\n        json::const_reference ref = j.at(\"/foo\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    // out_of_range.404\n    try\n    {\n        // try to use a JSON pointer that cannot be resolved\n        json::const_reference ref = j.at(\"/number/foo\"_json_pointer);\n    }\n    catch (const json::out_of_range& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    1\n\"foo\"\n[1,2]\n2\n[json.exception.parse_error.109] parse error: array index 'one' is not a number\n[json.exception.out_of_range.401] array index 4 is out of range\n[json.exception.out_of_range.402] array index '-' (2) is out of range\n[json.exception.out_of_range.403] key 'foo' not found\n[json.exception.out_of_range.404] unresolved reference token 'foo'\n
    "},{"location":"api/basic_json/at/#see-also","title":"See also","text":""},{"location":"api/basic_json/at/#version-history","title":"Version history","text":"
    1. Added in version 1.0.0.
    2. Added in version 1.0.0.
    3. Added in version 3.11.0.
    4. Added in version 2.0.0.
    "},{"location":"api/basic_json/back/","title":"nlohmann::basic_json::back","text":"
    reference back();\n\nconst_reference back() const;\n

    Returns a reference to the last element in the container. For a JSON container c, the expression c.back() is equivalent to

    auto tmp = c.end();\n--tmp;\nreturn *tmp;\n
    "},{"location":"api/basic_json/back/#return-value","title":"Return value","text":"

    In the case of a structured type (array or object), a reference to the last element is returned. In the case of number, string, boolean, or binary values, a reference to the value is returned.

    "},{"location":"api/basic_json/back/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

    "},{"location":"api/basic_json/back/#exceptions","title":"Exceptions","text":"

    If the JSON value is null, exception invalid_iterator.214 is thrown.

    "},{"location":"api/basic_json/back/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/back/#notes","title":"Notes","text":"

    Precondition

    The array or object must not be empty. Calling back on an empty array or object yields undefined behavior.

    "},{"location":"api/basic_json/back/#examples","title":"Examples","text":"Example

    The following code shows an example for back().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_boolean = true;\n    json j_number_integer = 17;\n    json j_number_float = 23.42;\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_object_empty(json::value_t::object);\n    json j_array = {1, 2, 4, 8, 16};\n    json j_array_empty(json::value_t::array);\n    json j_string = \"Hello, world\";\n\n    // call back()\n    std::cout << j_boolean.back() << '\\n';\n    std::cout << j_number_integer.back() << '\\n';\n    std::cout << j_number_float.back() << '\\n';\n    std::cout << j_object.back() << '\\n';\n    //std::cout << j_object_empty.back() << '\\n';  // undefined behavior\n    std::cout << j_array.back() << '\\n';\n    //std::cout << j_array_empty.back() << '\\n';   // undefined behavior\n    std::cout << j_string.back() << '\\n';\n\n    // back() called on a null value\n    try\n    {\n        json j_null;\n        j_null.back();\n    }\n    catch (const json::invalid_iterator& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    true\n17\n23.42\n2\n16\n\"Hello, world\"\n[json.exception.invalid_iterator.214] cannot get value\n
    "},{"location":"api/basic_json/back/#see-also","title":"See also","text":""},{"location":"api/basic_json/back/#version-history","title":"Version history","text":""},{"location":"api/basic_json/basic_json/","title":"nlohmann::basic_json::basic_json","text":"
    // (1)\nbasic_json(const value_t v);\n\n// (2)\nbasic_json(std::nullptr_t = nullptr) noexcept;\n\n// (3)\ntemplate<typename CompatibleType>\nbasic_json(CompatibleType&& val) noexcept(noexcept(\n           JSONSerializer<U>::to_json(std::declval<basic_json_t&>(),\n                                      std::forward<CompatibleType>(val))));\n\n// (4)\ntemplate<typename BasicJsonType>\nbasic_json(const BasicJsonType& val);\n\n// (5)\nbasic_json(initializer_list_t init,\n           bool type_deduction = true,\n           value_t manual_type = value_t::array);\n\n// (6)\nbasic_json(size_type cnt, const basic_json& val);\n\n// (7)\nbasic_json(iterator first, iterator last);\nbasic_json(const_iterator first, const_iterator last);\n\n// (8)\nbasic_json(const basic_json& other);\n\n// (9)\nbasic_json(basic_json&& other) noexcept;\n

    1. Create an empty JSON value with a given type. The value will be default initialized with an empty value which depends on the type:

      Value type initial value null null boolean false string \"\" number 0 object {} array [] binary empty array

      The postcondition of this constructor can be restored by calling clear().

    2. Create a null JSON value. It either takes a null pointer as parameter (explicitly creating null) or no parameter (implicitly creating null). The passed null pointer itself is not read -- it is only used to choose the right constructor.

    3. This is a \"catch all\" constructor for all compatible JSON types; that is, types for which a to_json() method exists. The constructor forwards the parameter val to that method (to json_serializer<U>::to_json method with U = uncvref_t<CompatibleType>, to be exact).

      Template type CompatibleType includes, but is not limited to, the following types:

      • arrays: array_t and all kinds of compatible containers such as std::vector, std::deque, std::list, std::forward_list, std::array, std::valarray, std::set, std::unordered_set, std::multiset, and std::unordered_multiset with a value_type from which a basic_json value can be constructed.
      • objects: object_t and all kinds of compatible associative containers such as std::map, std::unordered_map, std::multimap, and std::unordered_multimap with a key_type compatible to string_t and a value_type from which a basic_json value can be constructed.
      • strings: string_t, string literals, and all compatible string containers can be used.
      • numbers: number_integer_t, number_unsigned_t, number_float_t, and all convertible number types such as int, size_t, int64_t, float or double can be used.
      • boolean: boolean_t / bool can be used.
      • binary: binary_t / std::vector<uint8_t> may be used; unfortunately because string literals cannot be distinguished from binary character arrays by the C++ type system, all types compatible with const char* will be directed to the string constructor instead. This is both for backwards compatibility and due to the fact that a binary type is not a standard JSON type.

      See the examples below.

    4. This is a constructor for existing basic_json types. It does not hijack copy/move constructors, since the parameter has different template arguments than the current ones.

      The constructor tries to convert the internal m_value of the parameter. Each member value (object, array, string, etc.) is serialized via the corresponding to_json() overload. For objects and strings, the conversion requires that the target basic_json type's object_t::key_type (or string_t) be directly constructible from the source type's corresponding member type via is_constructible. If this requirement is not met, the conversion does not fail to compile; instead, it silently falls back to the array-conversion path, which represents objects as arrays of [key, value] pairs and strings as arrays of character codes. This is a known limitation tracked in issue #3425.

    5. Creates a JSON value of type array or object from the passed initializer list init. In case type_deduction is true (default), the type of the JSON value to be created is deducted from the initializer list init according to the following rules:

      1. If the list is empty, an empty JSON object value {} is created.
      2. If the list consists of pairs whose first element is a string, a JSON object value is created where the first elements of the pairs are treated as keys and the second elements are as values.
      3. In all other cases, an array is created.

      The rules aim to create the best fit between a C++ initializer list and JSON values. The rationale is as follows:

      1. The empty initializer list is written as {} which is exactly an empty JSON object.
      2. C++ has no way of describing mapped types other than to list a list of pairs. As JSON requires that keys must be of type string, rule 2 is the weakest constraint one can pose on initializer lists to interpret them as an object.
      3. In all other cases, the initializer list could not be interpreted as a JSON object type, so interpreting it as a JSON array type is safe.

      With the rules described above, the following JSON values cannot be expressed by an initializer list:

      • the empty array ([]): use array(initializer_list_t) with an empty initializer list in this case
      • arrays whose elements satisfy rule 2: use array(initializer_list_t) with the same initializer list in this case

      Function array() and object() force array and object creation from initializer lists, respectively.

    6. Constructs a JSON array value by creating cnt copies of a passed value. In case cnt is 0, an empty array is created.

    7. Constructs the JSON value with the contents of the range [first, last). The semantics depend on the different types a JSON value can have:

      • In case of a null type, invalid_iterator.206 is thrown.
      • In case of other primitive types (number, boolean, or string), first must be begin() and last must be end(). In this case, the value is copied. Otherwise, invalid_iterator.204 is thrown.
      • In case of structured types (array, object), the constructor behaves as similar versions for std::vector or std::map; that is, a JSON array or object is constructed from the values in the range.

    8. Creates a copy of a given JSON value.

    9. Move constructor. Constructs a JSON value with the contents of the given value other using move semantics. It \"steals\" the resources from other and leaves it as JSON null value.

    "},{"location":"api/basic_json/basic_json/#template-parameters","title":"Template parameters","text":"CompatibleType

    a type such that:

    BasicJsonType:

    a type such that:

    Note: For cross-basic_json conversions to produce correct results, the target basic_json's object_t::key_type and string_t must be directly constructible from the source basic_json's corresponding types. See the description of overload (4) above for details on what happens when this requirement is not met.

    U: uncvref_t<CompatibleType>"},{"location":"api/basic_json/basic_json/#parameters","title":"Parameters","text":"v (in) the type of the value to create val (in) the value to be forwarded to the respective constructor init (in) initializer list with JSON values type_deduction (in) internal parameter; when set to true, the type of the JSON value is deducted from the initializer list init; when set to false, the type provided via manual_type is forced. This mode is used by the functions array(initializer_list_t) and object(initializer_list_t). manual_type (in) internal parameter; when type_deduction is set to false, the created JSON value will use the provided type (only value_t::array and value_t::object are valid); when type_deduction is set to true, this parameter has no effect cnt (in) the number of JSON copies of val to create first (in) the beginning of the range to copy from (included) last (in) the end of the range to copy from (excluded) other (in) the JSON value to copy/move"},{"location":"api/basic_json/basic_json/#exception-safety","title":"Exception safety","text":"
    1. Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
    2. No-throw guarantee: this constructor never throws exceptions.
    3. Depends on the called constructor. For types directly supported by the library (i.e., all types for which no to_json() function was provided), a strong guarantee holds: if an exception is thrown, there are no changes to any JSON value.
    4. Depends on the called constructor. For types directly supported by the library (i.e., all types for which no to_json() function was provided), a strong guarantee holds: if an exception is thrown, there are no changes to any JSON value.
    5. Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
    6. Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
    7. Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
    8. Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
    9. No-throw guarantee: this constructor never throws exceptions.
    "},{"location":"api/basic_json/basic_json/#exceptions","title":"Exceptions","text":"
    1. (none)
    2. The function does not throw exceptions.
    3. (none)
    4. (none)
    5. The function can throw the following exceptions:
      • Throws type_error.301 if type_deduction is false, manual_type is value_t::object, but init contains an element which is not a pair whose first element is a string. In this case, the constructor could not create an object. If type_deduction would have been true, an array would have been created. See object(initializer_list_t) for an example.
    6. (none)
    7. The function can throw the following exceptions:
      • Throws invalid_iterator.201 if iterators first and last are not compatible (i.e., do not belong to the same JSON value). In this case, the range [first, last) is undefined.
      • Throws invalid_iterator.204 if iterators first and last belong to a primitive type (number, boolean, or string), but first does not point to the first element anymore. In this case, the range [first, last) is undefined. See the example code below.
      • Throws invalid_iterator.206 if iterators first and last belong to a null value. In this case, the range [first, last) is undefined.
    8. (none)
    9. The function does not throw exceptions.
    "},{"location":"api/basic_json/basic_json/#complexity","title":"Complexity","text":"
    1. Constant.
    2. Constant.
    3. Usually linear in the size of the passed val, also depending on the implementation of the called to_json() method.
    4. Usually linear in the size of the passed val, also depending on the implementation of the called to_json() method.
    5. Linear in the size of the initializer list init.
    6. Linear in cnt.
    7. Linear in distance between first and last.
    8. Linear in the size of other.
    9. Constant.
    "},{"location":"api/basic_json/basic_json/#notes","title":"Notes","text":""},{"location":"api/basic_json/basic_json/#examples","title":"Examples","text":"Example: (1) create an empty value with a given type

    The following code shows the constructor for different value_t values.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create the different JSON values with default values\n    json j_null(json::value_t::null);\n    json j_boolean(json::value_t::boolean);\n    json j_number_integer(json::value_t::number_integer);\n    json j_number_float(json::value_t::number_float);\n    json j_object(json::value_t::object);\n    json j_array(json::value_t::array);\n    json j_string(json::value_t::string);\n\n    // serialize the JSON values\n    std::cout << j_null << '\\n';\n    std::cout << j_boolean << '\\n';\n    std::cout << j_number_integer << '\\n';\n    std::cout << j_number_float << '\\n';\n    std::cout << j_object << '\\n';\n    std::cout << j_array << '\\n';\n    std::cout << j_string << '\\n';\n}\n

    Output:

    null\nfalse\n0\n0.0\n{}\n[]\n\"\"\n
    Example: (2) create a null object

    The following code shows the constructor with and without a null pointer parameter.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // implicitly create a JSON null value\n    json j1;\n\n    // explicitly create a JSON null value\n    json j2(nullptr);\n\n    // serialize the JSON null value\n    std::cout << j1 << '\\n' << j2 << '\\n';\n}\n

    Output:

    null\nnull\n
    Example: (3) create a JSON value from compatible types

    The following code shows the constructor with several compatible types.

    #include <iostream>\n#include <deque>\n#include <list>\n#include <forward_list>\n#include <set>\n#include <unordered_map>\n#include <unordered_set>\n#include <valarray>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // ============\n    // object types\n    // ============\n\n    // create an object from an object_t value\n    json::object_t object_value = { {\"one\", 1}, {\"two\", 2} };\n    json j_object_t(object_value);\n\n    // create an object from std::map\n    std::map<std::string, int> c_map\n    {\n        {\"one\", 1}, {\"two\", 2}, {\"three\", 3}\n    };\n    json j_map(c_map);\n\n    // create an object from std::unordered_map\n    std::unordered_map<const char*, double> c_umap\n    {\n        {\"one\", 1.2}, {\"two\", 2.3}, {\"three\", 3.4}\n    };\n    json j_umap(c_umap);\n\n    // create an object from std::multimap\n    std::multimap<std::string, bool> c_mmap\n    {\n        {\"one\", true}, {\"two\", true}, {\"three\", false}, {\"three\", true}\n    };\n    json j_mmap(c_mmap); // only one entry for key \"three\" is used\n\n    // create an object from std::unordered_multimap\n    std::unordered_multimap<std::string, bool> c_ummap\n    {\n        {\"one\", true}, {\"two\", true}, {\"three\", false}, {\"three\", true}\n    };\n    json j_ummap(c_ummap); // only one entry for key \"three\" is used\n\n    // serialize the JSON objects\n    std::cout << j_object_t << '\\n';\n    std::cout << j_map << '\\n';\n    std::cout << j_umap << '\\n';\n    std::cout << j_mmap << '\\n';\n    std::cout << j_ummap << \"\\n\\n\";\n\n    // ===========\n    // array types\n    // ===========\n\n    // create an array from an array_t value\n    json::array_t array_value = {\"one\", \"two\", 3, 4.5, false};\n    json j_array_t(array_value);\n\n    // create an array from std::vector\n    std::vector<int> c_vector {1, 2, 3, 4};\n    json j_vec(c_vector);\n\n    // create an array from std::valarray\n    std::valarray<short> c_valarray {10, 9, 8, 7};\n    json j_valarray(c_valarray);\n\n    // create an array from std::deque\n    std::deque<double> c_deque {1.2, 2.3, 3.4, 5.6};\n    json j_deque(c_deque);\n\n    // create an array from std::list\n    std::list<bool> c_list {true, true, false, true};\n    json j_list(c_list);\n\n    // create an array from std::forward_list\n    std::forward_list<std::int64_t> c_flist {12345678909876, 23456789098765, 34567890987654, 45678909876543};\n    json j_flist(c_flist);\n\n    // create an array from std::array\n    std::array<unsigned long, 4> c_array {{1, 2, 3, 4}};\n    json j_array(c_array);\n\n    // create an array from std::set\n    std::set<std::string> c_set {\"one\", \"two\", \"three\", \"four\", \"one\"};\n    json j_set(c_set); // only one entry for \"one\" is used\n\n    // create an array from std::unordered_set\n    std::unordered_set<std::string> c_uset {\"one\", \"two\", \"three\", \"four\", \"one\"};\n    json j_uset(c_uset); // only one entry for \"one\" is used\n\n    // create an array from std::multiset\n    std::multiset<std::string> c_mset {\"one\", \"two\", \"one\", \"four\"};\n    json j_mset(c_mset); // both entries for \"one\" are used\n\n    // create an array from std::unordered_multiset\n    std::unordered_multiset<std::string> c_umset {\"one\", \"two\", \"one\", \"four\"};\n    json j_umset(c_umset); // both entries for \"one\" are used\n\n    // serialize the JSON arrays\n    std::cout << j_array_t << '\\n';\n    std::cout << j_vec << '\\n';\n    std::cout << j_valarray << '\\n';\n    std::cout << j_deque << '\\n';\n    std::cout << j_list << '\\n';\n    std::cout << j_flist << '\\n';\n    std::cout << j_array << '\\n';\n    std::cout << j_set << '\\n';\n    std::cout << j_uset << '\\n';\n    std::cout << j_mset << '\\n';\n    std::cout << j_umset << \"\\n\\n\";\n\n    // ============\n    // string types\n    // ============\n\n    // create string from a string_t value\n    json::string_t string_value = \"The quick brown fox jumps over the lazy dog.\";\n    json j_string_t(string_value);\n\n    // create a JSON string directly from a string literal\n    json j_string_literal(\"The quick brown fox jumps over the lazy dog.\");\n\n    // create string from std::string\n    std::string s_stdstring = \"The quick brown fox jumps over the lazy dog.\";\n    json j_stdstring(s_stdstring);\n\n    // serialize the JSON strings\n    std::cout << j_string_t << '\\n';\n    std::cout << j_string_literal << '\\n';\n    std::cout << j_stdstring << \"\\n\\n\";\n\n    // ============\n    // number types\n    // ============\n\n    // create a JSON number from number_integer_t\n    json::number_integer_t value_integer_t = -42;\n    json j_integer_t(value_integer_t);\n\n    // create a JSON number from number_unsigned_t\n    json::number_integer_t value_unsigned_t = 17;\n    json j_unsigned_t(value_unsigned_t);\n\n    // create a JSON number from an anonymous enum\n    enum { enum_value = 17 };\n    json j_enum(enum_value);\n\n    // create values of different integer types\n    short n_short = 42;\n    int n_int = -23;\n    long n_long = 1024;\n    int_least32_t n_int_least32_t = -17;\n    uint8_t n_uint8_t = 8;\n\n    // create (integer) JSON numbers\n    json j_short(n_short);\n    json j_int(n_int);\n    json j_long(n_long);\n    json j_int_least32_t(n_int_least32_t);\n    json j_uint8_t(n_uint8_t);\n\n    // create values of different floating-point types\n    json::number_float_t v_ok = 3.141592653589793;\n    json::number_float_t v_nan = NAN;\n    json::number_float_t v_infinity = INFINITY;\n\n    // create values of different floating-point types\n    float n_float = 42.23;\n    float n_float_nan = 1.0f / 0.0f;\n    double n_double = 23.42;\n\n    // create (floating point) JSON numbers\n    json j_ok(v_ok);\n    json j_nan(v_nan);\n    json j_infinity(v_infinity);\n    json j_float(n_float);\n    json j_float_nan(n_float_nan);\n    json j_double(n_double);\n\n    // serialize the JSON numbers\n    std::cout << j_integer_t << '\\n';\n    std::cout << j_unsigned_t << '\\n';\n    std::cout << j_enum << '\\n';\n    std::cout << j_short << '\\n';\n    std::cout << j_int << '\\n';\n    std::cout << j_long << '\\n';\n    std::cout << j_int_least32_t << '\\n';\n    std::cout << j_uint8_t << '\\n';\n    std::cout << j_ok << '\\n';\n    std::cout << j_nan << '\\n';\n    std::cout << j_infinity << '\\n';\n    std::cout << j_float << '\\n';\n    std::cout << j_float_nan << '\\n';\n    std::cout << j_double << \"\\n\\n\";\n\n    // =============\n    // boolean types\n    // =============\n\n    // create boolean values\n    json j_truth = true;\n    json j_falsity = false;\n\n    // serialize the JSON booleans\n    std::cout << j_truth << '\\n';\n    std::cout << j_falsity << '\\n';\n}\n

    Output:

    {\"one\":1,\"two\":2}\n{\"one\":1,\"three\":3,\"two\":2}\n{\"one\":1.2,\"three\":3.4,\"two\":2.3}\n{\"one\":true,\"three\":false,\"two\":true}\n{\"one\":true,\"three\":false,\"two\":true}\n\n[\"one\",\"two\",3,4.5,false]\n[1,2,3,4]\n[10,9,8,7]\n[1.2,2.3,3.4,5.6]\n[true,true,false,true]\n[12345678909876,23456789098765,34567890987654,45678909876543]\n[1,2,3,4]\n[\"four\",\"one\",\"three\",\"two\"]\n[\"four\",\"three\",\"two\",\"one\"]\n[\"four\",\"one\",\"one\",\"two\"]\n[\"four\",\"two\",\"one\",\"one\"]\n\n\"The quick brown fox jumps over the lazy dog.\"\n\"The quick brown fox jumps over the lazy dog.\"\n\"The quick brown fox jumps over the lazy dog.\"\n\n-42\n17\n17\n42\n-23\n1024\n-17\n8\n3.141592653589793\nnull\nnull\n42.22999954223633\nnull\n23.42\n\ntrue\nfalse\n

    Note the output is platform-dependent.

    Example: (5) create a container (array or object) from an initializer list

    The example below shows how JSON values are created from initializer lists.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_empty_init_list = json({});\n    json j_object = { {\"one\", 1}, {\"two\", 2} };\n    json j_array = {1, 2, 3, 4};\n    json j_nested_object = { {\"one\", {1}}, {\"two\", {1, 2}} };\n    json j_nested_array = { {{1}, \"one\"}, {{1, 2}, \"two\"} };\n\n    // serialize the JSON value\n    std::cout << j_empty_init_list << '\\n';\n    std::cout << j_object << '\\n';\n    std::cout << j_array << '\\n';\n    std::cout << j_nested_object << '\\n';\n    std::cout << j_nested_array << '\\n';\n}\n

    Output:

    {}\n{\"one\":1,\"two\":2}\n[1,2,3,4]\n{\"one\":[1],\"two\":[1,2]}\n[[[1],\"one\"],[[1,2],\"two\"]]\n
    Example: (6) construct an array with count copies of a given value

    The following code shows examples for creating arrays with several copies of a given value.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array by creating copies of a JSON value\n    json value = \"Hello\";\n    json array_0 = json(0, value);\n    json array_1 = json(1, value);\n    json array_5 = json(5, value);\n\n    // serialize the JSON arrays\n    std::cout << array_0 << '\\n';\n    std::cout << array_1 << '\\n';\n    std::cout << array_5 << '\\n';\n}\n

    Output:

    []\n[\"Hello\"]\n[\"Hello\",\"Hello\",\"Hello\",\"Hello\",\"Hello\"]\n
    Example: (7) construct a JSON container given an iterator range

    The example below shows several ways to create JSON values by specifying a subrange with iterators.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_array = {\"alpha\", \"bravo\", \"charly\", \"delta\", \"easy\"};\n    json j_number = 42;\n    json j_object = {{\"one\", \"eins\"}, {\"two\", \"zwei\"}};\n\n    // create copies using iterators\n    json j_array_range(j_array.begin() + 1, j_array.end() - 2);\n    json j_number_range(j_number.begin(), j_number.end());\n    json j_object_range(j_object.begin(), j_object.find(\"two\"));\n\n    // serialize the values\n    std::cout << j_array_range << '\\n';\n    std::cout << j_number_range << '\\n';\n    std::cout << j_object_range << '\\n';\n\n    // example for an exception\n    try\n    {\n        json j_invalid(j_number.begin() + 1, j_number.end());\n    }\n    catch (const json::invalid_iterator& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    [\"bravo\",\"charly\"]\n42\n{\"one\":\"eins\"}\n[json.exception.invalid_iterator.204] iterators out of range\n
    Example: (8) copy constructor

    The following code shows an example for the copy constructor.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON array\n    json j1 = {\"one\", \"two\", 3, 4.5, false};\n\n    // create a copy\n    json j2(j1);\n\n    // serialize the JSON array\n    std::cout << j1 << \" = \" << j2 << '\\n';\n    std::cout << std::boolalpha << (j1 == j2) << '\\n';\n}\n

    Output:

    [\"one\",\"two\",3,4.5,false] = [\"one\",\"two\",3,4.5,false]\ntrue\n
    Example: (9) move constructor

    The code below shows the move constructor explicitly called via std::move.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON value\n    json a = 23;\n\n    // move contents of a to b\n    json b(std::move(a));\n\n    // serialize the JSON arrays\n    std::cout << a << '\\n';\n    std::cout << b << '\\n';\n}\n

    Output:

    null\n23\n
    "},{"location":"api/basic_json/basic_json/#version-history","title":"Version history","text":"
    1. Since version 1.0.0.
    2. Since version 1.0.0.
    3. Since version 2.1.0.
    4. Since version 3.2.0.
    5. Since version 1.0.0.
    6. Since version 1.0.0.
    7. Since version 1.0.0.
    8. Since version 1.0.0.
    9. Since version 1.0.0.
    "},{"location":"api/basic_json/begin/","title":"nlohmann::basic_json::begin","text":"
    iterator begin() noexcept;\nconst_iterator begin() const noexcept;\n

    Returns an iterator to the first element.

    "},{"location":"api/basic_json/begin/#return-value","title":"Return value","text":"

    iterator to the first element

    "},{"location":"api/basic_json/begin/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/begin/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/begin/#examples","title":"Examples","text":"Example

    The following code shows an example for begin().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array value\n    json array = {1, 2, 3, 4, 5};\n\n    // get an iterator to the first element\n    json::iterator it = array.begin();\n\n    // serialize the element that the iterator points to\n    std::cout << *it << '\\n';\n}\n

    Output:

    1\n
    "},{"location":"api/basic_json/begin/#version-history","title":"Version history","text":""},{"location":"api/basic_json/binary/","title":"nlohmann::basic_json::binary","text":"
    // (1)\nstatic basic_json binary(const typename binary_t::container_type& init);\nstatic basic_json binary(typename binary_t::container_type&& init);\n\n// (2)\nstatic basic_json binary(const typename binary_t::container_type& init,\n                         std::uint8_t subtype);\nstatic basic_json binary(typename binary_t::container_type&& init,\n                         std::uint8_t subtype);\n
    1. Creates a JSON binary array value from a given binary container.
    2. Creates a JSON binary array value from a given binary container with subtype.

    Binary values are part of various binary formats, such as CBOR, MessagePack, and BSON. This constructor is used to create a value for serialization to those formats.

    "},{"location":"api/basic_json/binary/#parameters","title":"Parameters","text":"init (in) container containing bytes to use as a binary type subtype (in) subtype to use in CBOR, MessagePack, and BSON"},{"location":"api/basic_json/binary/#return-value","title":"Return value","text":"

    JSON binary array value

    "},{"location":"api/basic_json/binary/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

    "},{"location":"api/basic_json/binary/#complexity","title":"Complexity","text":"

    Linear in the size of init; constant for typename binary_t::container_type&& init versions.

    "},{"location":"api/basic_json/binary/#notes","title":"Notes","text":"

    Note, this function exists because of the difficulty in correctly specifying the correct template overload in the standard value ctor, as both JSON arrays and JSON binary arrays are backed with some form of a std::vector. Because JSON binary arrays are a non-standard extension, it was decided that it would be best to prevent automatic initialization of a binary array type, for backwards compatibility and so it does not happen on accident.

    "},{"location":"api/basic_json/binary/#examples","title":"Examples","text":"Example

    The following code shows how to create a binary value.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a binary vector\n    std::vector<std::uint8_t> vec = {0xCA, 0xFE, 0xBA, 0xBE};\n\n    // create a binary JSON value with subtype 42\n    json j = json::binary(vec, 42);\n\n    // output type and subtype\n    std::cout << \"type: \" << j.type_name() << \", subtype: \" << j.get_binary().subtype() << std::endl;\n}\n

    Output:

    type: binary, subtype: 42\n
    "},{"location":"api/basic_json/binary/#version-history","title":"Version history","text":""},{"location":"api/basic_json/binary_t/","title":"nlohmann::basic_json::binary_t","text":"
    using binary_t = byte_container_with_subtype<BinaryType>;\n

    This type is a type designed to carry binary data that appears in various serialized formats, such as CBOR's Major Type 2, MessagePack's bin, and BSON's generic binary subtype. This type is NOT a part of standard JSON and exists solely for compatibility with these binary types. As such, it is simply defined as an ordered sequence of zero or more byte values.

    Additionally, as an implementation detail, the subtype of the binary data is carried around as a std::uint64_t, which is compatible with both of the binary data formats that use binary subtyping, (though the specific numbering is incompatible with each other, and it is up to the user to translate between them). The subtype is added to BinaryType via the helper type byte_container_with_subtype.

    CBOR's RFC 7049 describes this type as:

    Major type 2: a byte string. The string's length in bytes is represented following the rules for positive integers (major type 0).

    MessagePack's documentation on the bin type family describes this type as:

    Bin format family stores a byte array in 2, 3, or 5 bytes of extra bytes in addition to the size of the byte array.

    BSON's specifications describe several binary types; however, this type is intended to represent the generic binary type which has the description:

    Generic binary subtype - This is the most commonly used binary subtype and should be the 'default' for drivers and tools.

    None of these impose any limitations on the internal representation other than the basic unit of storage be some type of array whose parts are decomposable into bytes.

    The default representation of this binary format is a std::vector<std::uint8_t>, which is a very common way to represent a byte array in modern C++.

    "},{"location":"api/basic_json/binary_t/#template-parameters","title":"Template parameters","text":"BinaryType container type to store arrays"},{"location":"api/basic_json/binary_t/#notes","title":"Notes","text":""},{"location":"api/basic_json/binary_t/#default-type","title":"Default type","text":"

    The default values for BinaryType is std::vector<std::uint8_t>.

    "},{"location":"api/basic_json/binary_t/#storage","title":"Storage","text":"

    Binary Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of the type binary_t* must be dereferenced.

    "},{"location":"api/basic_json/binary_t/#notes-on-subtypes","title":"Notes on subtypes","text":""},{"location":"api/basic_json/binary_t/#examples","title":"Examples","text":"Example

    The following code shows that binary_t is by default, a typedef to nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    std::cout << std::boolalpha << std::is_same<nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>, json::binary_t>::value << std::endl;\n}\n

    Output:

    true\n
    "},{"location":"api/basic_json/binary_t/#see-also","title":"See also","text":""},{"location":"api/basic_json/binary_t/#version-history","title":"Version history","text":""},{"location":"api/basic_json/boolean_t/","title":"nlohmann::basic_json::boolean_t","text":"
    using boolean_t = BooleanType;\n

    The type used to store JSON booleans.

    RFC 8259 implicitly describes a boolean as a type which differentiates the two literals true and false.

    To store boolean values in C++, a type is defined by the template parameter BooleanType which chooses the type to use.

    "},{"location":"api/basic_json/boolean_t/#notes","title":"Notes","text":""},{"location":"api/basic_json/boolean_t/#default-type","title":"Default type","text":"

    With the default values for BooleanType (bool), the default value for boolean_t is bool.

    "},{"location":"api/basic_json/boolean_t/#storage","title":"Storage","text":"

    Boolean values are stored directly inside a basic_json type.

    "},{"location":"api/basic_json/boolean_t/#examples","title":"Examples","text":"Example

    The following code shows that boolean_t is by default, a typedef to bool.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    std::cout << std::boolalpha << std::is_same<bool, json::boolean_t>::value << std::endl;\n}\n

    Output:

    true\n
    "},{"location":"api/basic_json/boolean_t/#version-history","title":"Version history","text":""},{"location":"api/basic_json/cbegin/","title":"nlohmann::basic_json::cbegin","text":"
    const_iterator cbegin() const noexcept;\n

    Returns an iterator to the first element.

    "},{"location":"api/basic_json/cbegin/#return-value","title":"Return value","text":"

    iterator to the first element

    "},{"location":"api/basic_json/cbegin/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/cbegin/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/cbegin/#examples","title":"Examples","text":"Example

    The following code shows an example for cbegin().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array value\n    const json array = {1, 2, 3, 4, 5};\n\n    // get an iterator to the first element\n    json::const_iterator it = array.cbegin();\n\n    // serialize the element that the iterator points to\n    std::cout << *it << '\\n';\n}\n

    Output:

    1\n
    "},{"location":"api/basic_json/cbegin/#version-history","title":"Version history","text":""},{"location":"api/basic_json/cbor_tag_handler_t/","title":"nlohmann::basic_json::cbor_tag_handler_t","text":"
    enum class cbor_tag_handler_t\n{\n    error,\n    ignore,\n    store\n};\n

    This enumeration is used in the from_cbor function to choose how to treat tags:

    error throw a parse_error exception in case of a tag ignore ignore tags store store tagged values as binary container with subtype (for bytes 0xd8..0xdb)"},{"location":"api/basic_json/cbor_tag_handler_t/#examples","title":"Examples","text":"Example

    The example below shows how the different values of the cbor_tag_handler_t influence the behavior of from_cbor when reading a tagged byte string.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // tagged byte string\n    std::vector<std::uint8_t> vec = {{0xd8, 0x42, 0x44, 0xcA, 0xfe, 0xba, 0xbe}};\n\n    // cbor_tag_handler_t::error throws\n    try\n    {\n        auto b_throw_on_tag = json::from_cbor(vec, true, true, json::cbor_tag_handler_t::error);\n    }\n    catch (const json::parse_error& e)\n    {\n        std::cout << e.what() << std::endl;\n    }\n\n    // cbor_tag_handler_t::ignore ignores the tag\n    auto b_ignore_tag = json::from_cbor(vec, true, true, json::cbor_tag_handler_t::ignore);\n    std::cout << b_ignore_tag << std::endl;\n\n    // cbor_tag_handler_t::store stores the tag as binary subtype\n    auto b_store_tag = json::from_cbor(vec, true, true, json::cbor_tag_handler_t::store);\n    std::cout << b_store_tag << std::endl;\n}\n

    Output:

    [json.exception.parse_error.112] parse error at byte 1: syntax error while parsing CBOR value: invalid byte: 0xD8\n{\"bytes\":[202,254,186,190],\"subtype\":null}\n{\"bytes\":[202,254,186,190],\"subtype\":66}\n
    "},{"location":"api/basic_json/cbor_tag_handler_t/#version-history","title":"Version history","text":""},{"location":"api/basic_json/cend/","title":"nlohmann::basic_json::cend","text":"
    const_iterator cend() const noexcept;\n

    Returns an iterator to one past the last element.

    "},{"location":"api/basic_json/cend/#return-value","title":"Return value","text":"

    iterator one past the last element

    "},{"location":"api/basic_json/cend/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/cend/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/cend/#examples","title":"Examples","text":"Example

    The following code shows an example for cend().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array value\n    json array = {1, 2, 3, 4, 5};\n\n    // get an iterator to one past the last element\n    json::const_iterator it = array.cend();\n\n    // decrement the iterator to point to the last element\n    --it;\n\n    // serialize the element that the iterator points to\n    std::cout << *it << '\\n';\n}\n

    Output:

    5\n
    "},{"location":"api/basic_json/cend/#version-history","title":"Version history","text":""},{"location":"api/basic_json/clear/","title":"nlohmann::basic_json::clear","text":"
    void clear() noexcept;\n

    Clears the content of a JSON value and resets it to the default value as if basic_json(value_t) would have been called with the current value type from type():

    Value type initial value null null boolean false string \"\" number 0 binary An empty byte vector object {} array []

    Has the same effect as calling

    *this = basic_json(type());\n
    "},{"location":"api/basic_json/clear/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this function never throws exceptions.

    "},{"location":"api/basic_json/clear/#complexity","title":"Complexity","text":"

    Linear in the size of the JSON value.

    "},{"location":"api/basic_json/clear/#notes","title":"Notes","text":"

    All iterators, pointers, and references related to this container are invalidated.

    "},{"location":"api/basic_json/clear/#examples","title":"Examples","text":"Example

    The example below shows the effect of clear() to different JSON types.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_null;\n    json j_boolean = true;\n    json j_number_integer = 17;\n    json j_number_float = 23.42;\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_array = {1, 2, 4, 8, 16};\n    json j_string = \"Hello, world\";\n\n    // call clear()\n    j_null.clear();\n    j_boolean.clear();\n    j_number_integer.clear();\n    j_number_float.clear();\n    j_object.clear();\n    j_array.clear();\n    j_string.clear();\n\n    // serialize the cleared values()\n    std::cout << j_null << '\\n';\n    std::cout << j_boolean << '\\n';\n    std::cout << j_number_integer << '\\n';\n    std::cout << j_number_float << '\\n';\n    std::cout << j_object << '\\n';\n    std::cout << j_array << '\\n';\n    std::cout << j_string << '\\n';\n}\n

    Output:

    null\nfalse\n0\n0.0\n{}\n[]\n\"\"\n
    "},{"location":"api/basic_json/clear/#version-history","title":"Version history","text":""},{"location":"api/basic_json/contains/","title":"nlohmann::basic_json::contains","text":"
    // (1)\nbool contains(const typename object_t::key_type& key) const;\n\n// (2)\ntemplate<typename KeyType>\nbool contains(KeyType&& key) const;\n\n// (3)\nbool contains(const json_pointer& ptr) const;\n
    1. Check whether an element exists in a JSON object with a key equivalent to key. If the element is not found or the JSON value is not an object, false is returned.
    2. See 1. This overload is only available if KeyType is comparable with typename object_t::key_type and typename object_comparator_t::is_transparent denotes a type.
    3. Check whether the given JSON pointer ptr can be resolved in the current JSON value.
    "},{"location":"api/basic_json/contains/#template-parameters","title":"Template parameters","text":"KeyType A type for an object key other than json_pointer that is comparable with string_t using object_comparator_t. This can also be a string view (C++17)."},{"location":"api/basic_json/contains/#parameters","title":"Parameters","text":"key (in) key value to check its existence. ptr (in) JSON pointer to check its existence."},{"location":"api/basic_json/contains/#return-value","title":"Return value","text":"
    1. true if an element with specified key exists. If no such element with such a key is found or the JSON value is not an object, false is returned.
    2. See 1.
    3. true if the JSON pointer can be resolved to a stored value, false otherwise.
    "},{"location":"api/basic_json/contains/#exception-safety","title":"Exception safety","text":"

    Strong exception safety: if an exception occurs, the original value stays intact.

    "},{"location":"api/basic_json/contains/#exceptions","title":"Exceptions","text":"
    1. The function does not throw exceptions.
    2. The function does not throw exceptions.
    3. The function does not throw exceptions.
    "},{"location":"api/basic_json/contains/#complexity","title":"Complexity","text":"

    Logarithmic in the size of the JSON object.

    "},{"location":"api/basic_json/contains/#notes","title":"Notes","text":"

    Postconditions

    If j.contains(x) returns true for a key or JSON pointer x, then it is safe to call j[x].

    "},{"location":"api/basic_json/contains/#examples","title":"Examples","text":"Example: (1) check with key

    The example shows how contains() is used.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    // create some JSON values\n    json j_object = R\"( {\"key\": \"value\"} )\"_json;\n    json j_array = R\"( [1, 2, 3] )\"_json;\n\n    // call contains\n    std::cout << std::boolalpha <<\n              \"j_object contains 'key': \" << j_object.contains(\"key\") << '\\n' <<\n              \"j_object contains 'another': \" << j_object.contains(\"another\") << '\\n' <<\n              \"j_array contains 'key': \" << j_array.contains(\"key\") << std::endl;\n}\n

    Output:

    j_object contains 'key': true\nj_object contains 'another': false\nj_array contains 'key': false\n
    Example: (2) check with key using string_view

    The example shows how contains() is used.

    #include <iostream>\n#include <string_view>\n#include <nlohmann/json.hpp>\n\nusing namespace std::string_view_literals;\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    // create some JSON values\n    json j_object = R\"( {\"key\": \"value\"} )\"_json;\n    json j_array = R\"( [1, 2, 3] )\"_json;\n\n    // call contains\n    std::cout << std::boolalpha <<\n              \"j_object contains 'key': \" << j_object.contains(\"key\"sv) << '\\n' <<\n              \"j_object contains 'another': \" << j_object.contains(\"another\"sv) << '\\n' <<\n              \"j_array contains 'key': \" << j_array.contains(\"key\"sv) << std::endl;\n}\n

    Output:

    j_object contains 'key': true\nj_object contains 'another': false\nj_array contains 'key': false\n
    Example: (3) check with JSON pointer

    The example shows how contains() is used.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    // create a JSON value\n    json j =\n    {\n        {\"number\", 1}, {\"string\", \"foo\"}, {\"array\", {1, 2}}\n    };\n\n    std::cout << std::boolalpha\n              << j.contains(\"/number\"_json_pointer) << '\\n'\n              << j.contains(\"/string\"_json_pointer) << '\\n'\n              << j.contains(\"/array\"_json_pointer) << '\\n'\n              << j.contains(\"/array/1\"_json_pointer) << '\\n'\n              << j.contains(\"/array/-\"_json_pointer) << '\\n'\n              << j.contains(\"/array/4\"_json_pointer) << '\\n'\n              << j.contains(\"/baz\"_json_pointer) << std::endl;\n\n    try\n    {\n        // try to use an array index with leading '0'\n        j.contains(\"/array/01\"_json_pointer);\n    }\n    catch (const json::parse_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n\n    try\n    {\n        // try to use an array index that is not a number\n        j.contains(\"/array/one\"_json_pointer);\n    }\n    catch (const json::parse_error& e)\n    {\n        std::cout << e.what() << '\\n';\n    }\n}\n

    Output:

    true\ntrue\ntrue\ntrue\nfalse\nfalse\nfalse\n
    "},{"location":"api/basic_json/contains/#see-also","title":"See also","text":""},{"location":"api/basic_json/contains/#version-history","title":"Version history","text":"
    1. Added in version 3.11.0.
    2. Added in version 3.6.0. Extended template KeyType to support comparable types in version 3.11.0.
    3. Added in version 3.7.0.
    "},{"location":"api/basic_json/count/","title":"nlohmann::basic_json::count","text":"
    // (1)\nsize_type count(const typename object_t::key_type& key) const;\n\n// (2)\ntemplate<typename KeyType>\nsize_type count(KeyType&& key) const;\n
    1. Returns the number of elements with key key. If ObjectType is the default std::map type, the return value will always be 0 (key was not found) or 1 (key was found).
    2. See 1. This overload is only available if KeyType is comparable with typename object_t::key_type and typename object_comparator_t::is_transparent denotes a type.
    "},{"location":"api/basic_json/count/#template-parameters","title":"Template parameters","text":"KeyType A type for an object key other than json_pointer that is comparable with string_t using object_comparator_t. This can also be a string view (C++17)."},{"location":"api/basic_json/count/#parameters","title":"Parameters","text":"key (in) key value of the element to count."},{"location":"api/basic_json/count/#return-value","title":"Return value","text":"

    Number of elements with key key. If the JSON value is not an object, the return value will be 0.

    "},{"location":"api/basic_json/count/#exception-safety","title":"Exception safety","text":"

    Strong exception safety: if an exception occurs, the original value stays intact.

    "},{"location":"api/basic_json/count/#complexity","title":"Complexity","text":"

    Logarithmic in the size of the JSON object.

    "},{"location":"api/basic_json/count/#notes","title":"Notes","text":"

    This method always returns 0 when executed on a JSON type that is not an object.

    "},{"location":"api/basic_json/count/#examples","title":"Examples","text":"Example: (1) count number of elements

    The example shows how count() is used.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n\n    // call count()\n    auto count_two = j_object.count(\"two\");\n    auto count_three = j_object.count(\"three\");\n\n    // print values\n    std::cout << \"number of elements with key \\\"two\\\": \" << count_two << '\\n';\n    std::cout << \"number of elements with key \\\"three\\\": \" << count_three << '\\n';\n}\n

    Output:

    number of elements with key \"two\": 1\nnumber of elements with key \"three\": 0\n
    Example: (2) count number of elements using string_view

    The example shows how count() is used.

    #include <iostream>\n#include <string_view>\n#include <nlohmann/json.hpp>\n\nusing namespace std::string_view_literals;\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n\n    // call count()\n    auto count_two = j_object.count(\"two\"sv);\n    auto count_three = j_object.count(\"three\"sv);\n\n    // print values\n    std::cout << \"number of elements with key \\\"two\\\": \" << count_two << '\\n';\n    std::cout << \"number of elements with key \\\"three\\\": \" << count_three << '\\n';\n}\n

    Output:

    number of elements with key \"two\": 1\nnumber of elements with key \"three\": 0\n
    "},{"location":"api/basic_json/count/#see-also","title":"See also","text":""},{"location":"api/basic_json/count/#version-history","title":"Version history","text":"
    1. Added in version 3.11.0.
    2. Added in version 1.0.0. Changed parameter key type to KeyType&& in version 3.11.0.
    "},{"location":"api/basic_json/crbegin/","title":"nlohmann::basic_json::crbegin","text":"
    const_reverse_iterator crbegin() const noexcept;\n

    Returns an iterator to the reverse-beginning; that is, the last element.

    "},{"location":"api/basic_json/crbegin/#return-value","title":"Return value","text":"

    reverse iterator to the last element

    "},{"location":"api/basic_json/crbegin/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/crbegin/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/crbegin/#examples","title":"Examples","text":"Example

    The following code shows an example for crbegin().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array value\n    json array = {1, 2, 3, 4, 5};\n\n    // get an iterator to the reverse-beginning\n    json::const_reverse_iterator it = array.crbegin();\n\n    // serialize the element that the iterator points to\n    std::cout << *it << '\\n';\n}\n

    Output:

    5\n
    "},{"location":"api/basic_json/crbegin/#version-history","title":"Version history","text":""},{"location":"api/basic_json/crend/","title":"nlohmann::basic_json::crend","text":"
    const_reverse_iterator crend() const noexcept;\n

    Returns an iterator to the reverse-end; that is, one before the first element. This element acts as a placeholder, attempting to access it results in undefined behavior.

    "},{"location":"api/basic_json/crend/#return-value","title":"Return value","text":"

    reverse iterator to the element following the last element

    "},{"location":"api/basic_json/crend/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/crend/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/crend/#examples","title":"Examples","text":"Example

    The following code shows an example for crend().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array value\n    json array = {1, 2, 3, 4, 5};\n\n    // get an iterator to the reverse-end\n    json::const_reverse_iterator it = array.crend();\n\n    // increment the iterator to point to the first element\n    --it;\n\n    // serialize the element that the iterator points to\n    std::cout << *it << '\\n';\n}\n

    Output:

    1\n
    "},{"location":"api/basic_json/crend/#version-history","title":"Version history","text":""},{"location":"api/basic_json/default_object_comparator_t/","title":"nlohmann::basic_json::default_object_comparator_t","text":"
    using default_object_comparator_t = std::less<StringType>;  // until C++14\n\nusing default_object_comparator_t = std::less<>;            // since C++14\n

    The default comparator used by object_t.

    Since C++14 a transparent comparator is used which prevents unnecessary string construction when looking up a key in an object.

    The actual comparator used depends on object_t and can be obtained via object_comparator_t.

    "},{"location":"api/basic_json/default_object_comparator_t/#examples","title":"Examples","text":"Example

    The example below demonstrates the default comparator.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    std::cout << std::boolalpha\n              << \"one < two : \" << json::default_object_comparator_t{}(\"one\", \"two\") << \"\\n\"\n              << \"three < four : \" << json::default_object_comparator_t{}(\"three\", \"four\") << std::endl;\n}\n

    Output:

    one < two : true\nthree < four : false\n
    "},{"location":"api/basic_json/default_object_comparator_t/#version-history","title":"Version history","text":""},{"location":"api/basic_json/diff/","title":"nlohmann::basic_json::diff","text":"
    static basic_json diff(const basic_json& source,\n                       const basic_json& target);\n

    Creates a JSON Patch so that value source can be changed into the value target by calling patch function.

    For two JSON values source and target, the following code yields always true: 

    source.patch(diff(source, target)) == target;\n

    "},{"location":"api/basic_json/diff/#parameters","title":"Parameters","text":"source (in) JSON value to compare from target (in) JSON value to compare against"},{"location":"api/basic_json/diff/#return-value","title":"Return value","text":"

    a JSON patch to convert the source to target

    "},{"location":"api/basic_json/diff/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

    "},{"location":"api/basic_json/diff/#complexity","title":"Complexity","text":"

    Linear in the lengths of source and target.

    "},{"location":"api/basic_json/diff/#notes","title":"Notes","text":"

    Currently, only remove, add, and replace operations are generated.

    "},{"location":"api/basic_json/diff/#examples","title":"Examples","text":"Example

    The following code shows how a JSON patch is created as a diff for two JSON values.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\nusing namespace nlohmann::literals;\n\nint main()\n{\n    // the source document\n    json source = R\"(\n        {\n            \"baz\": \"qux\",\n            \"foo\": \"bar\"\n        }\n    )\"_json;\n\n    // the target document\n    json target = R\"(\n        {\n            \"baz\": \"boo\",\n            \"hello\": [\n                \"world\"\n            ]\n        }\n    )\"_json;\n\n    // create the patch\n    json patch = json::diff(source, target);\n\n    // roundtrip\n    json patched_source = source.patch(patch);\n\n    // output patch and roundtrip result\n    std::cout << std::setw(4) << patch << \"\\n\\n\"\n              << std::setw(4) << patched_source << std::endl;\n}\n

    Output:

    [\n    {\n        \"op\": \"replace\",\n        \"path\": \"/baz\",\n        \"value\": \"boo\"\n    },\n    {\n        \"op\": \"remove\",\n        \"path\": \"/foo\"\n    },\n    {\n        \"op\": \"add\",\n        \"path\": \"/hello\",\n        \"value\": [\n            \"world\"\n        ]\n    }\n]\n\n{\n    \"baz\": \"boo\",\n    \"hello\": [\n        \"world\"\n    ]\n}\n
    "},{"location":"api/basic_json/diff/#see-also","title":"See also","text":""},{"location":"api/basic_json/diff/#version-history","title":"Version history","text":""},{"location":"api/basic_json/dump/","title":"nlohmann::basic_json::dump","text":"
    string_t dump(const int indent = -1,\n              const char indent_char = ' ',\n              const bool ensure_ascii = false,\n              const error_handler_t error_handler = error_handler_t::strict) const;\n

    Serialization function for JSON values. The function tries to mimic Python's json.dumps() function, and currently supports its indent and ensure_ascii parameters.

    "},{"location":"api/basic_json/dump/#parameters","title":"Parameters","text":"indent (in) If indent is nonnegative, then array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. -1 (the default) selects the most compact representation. indent_char (in) The character to use for indentation if indent is greater than 0. The default is (space). ensure_ascii (in) If ensure_ascii is true, all non-ASCII characters in the output are escaped with \\uXXXX sequences, and the result consists of ASCII characters only. error_handler (in) how to react on decoding errors; there are three possible values (see error_handler_t: strict (throws an exception in case a decoding error occurs; default), replace (replace invalid UTF-8 sequences with U+FFFD), and ignore (ignore invalid UTF-8 sequences during serialization; all valid bytes are copied to the output unchanged, and invalid bytes are dropped))."},{"location":"api/basic_json/dump/#return-value","title":"Return value","text":"

    string containing the serialization of the JSON value

    "},{"location":"api/basic_json/dump/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

    "},{"location":"api/basic_json/dump/#exceptions","title":"Exceptions","text":"

    Throws type_error.316 if a string stored inside the JSON value is not UTF-8 encoded and error_handler is set to strict

    "},{"location":"api/basic_json/dump/#complexity","title":"Complexity","text":"

    Linear.

    "},{"location":"api/basic_json/dump/#notes","title":"Notes","text":"

    Binary values are serialized as an object containing two keys:

    "},{"location":"api/basic_json/dump/#examples","title":"Examples","text":"Example

    The following example shows the effect of different indent, indent_char, and ensure_ascii parameters to the result of the serialization.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_array = {1, 2, 4, 8, 16};\n    json j_string = \"Hell\u00f6 \ud83d\ude00!\";\n\n    // call dump()\n    std::cout << \"objects:\" << '\\n'\n              << j_object.dump() << \"\\n\\n\"\n              << j_object.dump(-1) << \"\\n\\n\"\n              << j_object.dump(0) << \"\\n\\n\"\n              << j_object.dump(4) << \"\\n\\n\"\n              << j_object.dump(1, '\\t') << \"\\n\\n\";\n\n    std::cout << \"arrays:\" << '\\n'\n              << j_array.dump() << \"\\n\\n\"\n              << j_array.dump(-1) << \"\\n\\n\"\n              << j_array.dump(0) << \"\\n\\n\"\n              << j_array.dump(4) << \"\\n\\n\"\n              << j_array.dump(1, '\\t') << \"\\n\\n\";\n\n    std::cout << \"strings:\" << '\\n'\n              << j_string.dump() << '\\n'\n              << j_string.dump(-1, ' ', true) << '\\n';\n\n    // create JSON value with invalid UTF-8 byte sequence\n    json j_invalid = \"\u00e4\\xA9\u00fc\";\n    try\n    {\n        std::cout << j_invalid.dump() << std::endl;\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << std::endl;\n    }\n\n    std::cout << \"string with replaced invalid characters: \"\n              << j_invalid.dump(-1, ' ', false, json::error_handler_t::replace)\n              << \"\\nstring with ignored invalid characters: \"\n              << j_invalid.dump(-1, ' ', false, json::error_handler_t::ignore)\n              << '\\n';\n}\n

    Output:

    objects:\n{\"one\":1,\"two\":2}\n\n{\"one\":1,\"two\":2}\n\n{\n\"one\": 1,\n\"two\": 2\n}\n\n{\n    \"one\": 1,\n    \"two\": 2\n}\n\n{\n    \"one\": 1,\n    \"two\": 2\n}\n\narrays:\n[1,2,4,8,16]\n\n[1,2,4,8,16]\n\n[\n1,\n2,\n4,\n8,\n16\n]\n\n[\n    1,\n    2,\n    4,\n    8,\n    16\n]\n\n[\n    1,\n    2,\n    4,\n    8,\n    16\n]\n\nstrings:\n\"Hell\u00f6 \ud83d\ude00!\"\n\"Hell\\u00f6 \\ud83d\\ude00!\"\n[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9\nstring with replaced invalid characters: \"\u00e4\ufffd\u00fc\"\nstring with ignored invalid characters: \"\u00e4\u00fc\"\n
    "},{"location":"api/basic_json/dump/#see-also","title":"See also","text":""},{"location":"api/basic_json/dump/#version-history","title":"Version history","text":""},{"location":"api/basic_json/emplace/","title":"nlohmann::basic_json::emplace","text":"
    template<class... Args>\nstd::pair<iterator, bool> emplace(Args&& ... args);\n

    Inserts a new element into a JSON object constructed in-place with the given args if there is no element with the key in the container. If the function is called on a JSON null value, an empty object is created before appending the value created from args.

    "},{"location":"api/basic_json/emplace/#template-parameters","title":"Template parameters","text":"Args compatible types to create a basic_json object"},{"location":"api/basic_json/emplace/#iterator-invalidation","title":"Iterator invalidation","text":"

    For ordered_json, adding a value to an object can yield a reallocation, in which case all iterators (including the end() iterator) and all references to the elements are invalidated.

    "},{"location":"api/basic_json/emplace/#parameters","title":"Parameters","text":"args (in) arguments to forward to a constructor of basic_json"},{"location":"api/basic_json/emplace/#return-value","title":"Return value","text":"

    a pair consisting of an iterator to the inserted element, or the already-existing element if no insertion happened, and a bool denoting whether the insertion took place.

    "},{"location":"api/basic_json/emplace/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

    "},{"location":"api/basic_json/emplace/#exceptions","title":"Exceptions","text":"

    Throws type_error.311 when called on a type other than JSON object or null; example: \"cannot use emplace() with number\"

    "},{"location":"api/basic_json/emplace/#complexity","title":"Complexity","text":"

    Logarithmic in the size of the container, O(log(size())).

    "},{"location":"api/basic_json/emplace/#examples","title":"Examples","text":"Example

    The example shows how emplace() can be used to add elements to a JSON object. Note how the null value was silently converted to a JSON object. Further note how no value is added if there was already one value stored with the same key.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json object = {{\"one\", 1}, {\"two\", 2}};\n    json null;\n\n    // print values\n    std::cout << object << '\\n';\n    std::cout << null << '\\n';\n\n    // add values\n    auto res1 = object.emplace(\"three\", 3);\n    null.emplace(\"A\", \"a\");\n    null.emplace(\"B\", \"b\");\n\n    // the following call will not add an object, because there is already\n    // a value stored at key \"B\"\n    auto res2 = null.emplace(\"B\", \"c\");\n\n    // print values\n    std::cout << object << '\\n';\n    std::cout << *res1.first << \" \" << std::boolalpha << res1.second << '\\n';\n\n    std::cout << null << '\\n';\n    std::cout << *res2.first << \" \" << std::boolalpha << res2.second << '\\n';\n}\n

    Output:

    {\"one\":1,\"two\":2}\nnull\n{\"one\":1,\"three\":3,\"two\":2}\n3 true\n{\"A\":\"a\",\"B\":\"b\"}\n\"b\" false\n
    "},{"location":"api/basic_json/emplace/#see-also","title":"See also","text":""},{"location":"api/basic_json/emplace/#version-history","title":"Version history","text":""},{"location":"api/basic_json/emplace_back/","title":"nlohmann::basic_json::emplace_back","text":"
    template<class... Args>\nreference emplace_back(Args&& ... args);\n

    Creates a JSON value from the passed parameters args to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending the value created from args.

    "},{"location":"api/basic_json/emplace_back/#template-parameters","title":"Template parameters","text":"Args compatible types to create a basic_json object"},{"location":"api/basic_json/emplace_back/#iterator-invalidation","title":"Iterator invalidation","text":"

    By adding an element to the end of the array, a reallocation can happen, in which case all iterators (including the end() iterator) and all references to the elements are invalidated. Otherwise, only the end() iterator is invalidated.

    "},{"location":"api/basic_json/emplace_back/#parameters","title":"Parameters","text":"args (in) arguments to forward to a constructor of basic_json"},{"location":"api/basic_json/emplace_back/#return-value","title":"Return value","text":"

    reference to the inserted element

    "},{"location":"api/basic_json/emplace_back/#exceptions","title":"Exceptions","text":"

    Throws type_error.311 when called on a type other than JSON array or null; example: \"cannot use emplace_back() with number\"

    "},{"location":"api/basic_json/emplace_back/#complexity","title":"Complexity","text":"

    Amortized constant.

    "},{"location":"api/basic_json/emplace_back/#examples","title":"Examples","text":"Example

    The example shows how emplace_back() can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json array = {1, 2, 3, 4, 5};\n    json null;\n\n    // print values\n    std::cout << array << '\\n';\n    std::cout << null << '\\n';\n\n    // add values\n    array.emplace_back(6);\n    null.emplace_back(\"first\");\n    null.emplace_back(3, \"second\");\n\n    // print values\n    std::cout << array << '\\n';\n    std::cout << null << '\\n';\n}\n

    Output:

    [1,2,3,4,5]\nnull\n[1,2,3,4,5,6]\n[\"first\",[\"second\",\"second\",\"second\"]]\n
    "},{"location":"api/basic_json/emplace_back/#see-also","title":"See also","text":""},{"location":"api/basic_json/emplace_back/#version-history","title":"Version history","text":""},{"location":"api/basic_json/empty/","title":"nlohmann::basic_json::empty","text":"
    bool empty() const noexcept;\n

    Checks if a JSON value has no elements (i.e., whether its size() is 0).

    "},{"location":"api/basic_json/empty/#return-value","title":"Return value","text":"

    The return value depends on the different types and is defined as follows:

    Value type return value null true boolean false string false number false binary false object result of function object_t::empty() array result of function array_t::empty()"},{"location":"api/basic_json/empty/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this function never throws exceptions.

    "},{"location":"api/basic_json/empty/#complexity","title":"Complexity","text":"

    Constant, as long as array_t and object_t satisfy the Container concept; that is, their empty() functions have constant complexity.

    "},{"location":"api/basic_json/empty/#possible-implementation","title":"Possible implementation","text":"
    bool empty() const noexcept\n{\n    return size() == 0;\n}\n
    "},{"location":"api/basic_json/empty/#notes","title":"Notes","text":"

    This function does not return whether a string stored as JSON value is empty -- it returns whether the JSON container itself is empty which is false in the case of a string.

    "},{"location":"api/basic_json/empty/#examples","title":"Examples","text":"Example

    The following code uses empty() to check if a JSON object contains any elements.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_null;\n    json j_boolean = true;\n    json j_number_integer = 17;\n    json j_number_float = 23.42;\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_object_empty(json::value_t::object);\n    json j_array = {1, 2, 4, 8, 16};\n    json j_array_empty(json::value_t::array);\n    json j_string = \"Hello, world\";\n\n    // call empty()\n    std::cout << std::boolalpha;\n    std::cout << j_null.empty() << '\\n';\n    std::cout << j_boolean.empty() << '\\n';\n    std::cout << j_number_integer.empty() << '\\n';\n    std::cout << j_number_float.empty() << '\\n';\n    std::cout << j_object.empty() << '\\n';\n    std::cout << j_object_empty.empty() << '\\n';\n    std::cout << j_array.empty() << '\\n';\n    std::cout << j_array_empty.empty() << '\\n';\n    std::cout << j_string.empty() << '\\n';\n}\n

    Output:

    true\nfalse\nfalse\nfalse\nfalse\ntrue\nfalse\ntrue\nfalse\n
    "},{"location":"api/basic_json/empty/#version-history","title":"Version history","text":""},{"location":"api/basic_json/end/","title":"nlohmann::basic_json::end","text":"
    iterator end() noexcept;\nconst_iterator end() const noexcept;\n

    Returns an iterator to one past the last element.

    "},{"location":"api/basic_json/end/#return-value","title":"Return value","text":"

    iterator one past the last element

    "},{"location":"api/basic_json/end/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/end/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/end/#examples","title":"Examples","text":"Example

    The following code shows an example for end().

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create an array value\n    json array = {1, 2, 3, 4, 5};\n\n    // get an iterator to one past the last element\n    json::iterator it = array.end();\n\n    // decrement the iterator to point to the last element\n    --it;\n\n    // serialize the element that the iterator points to\n    std::cout << *it << '\\n';\n}\n

    Output:

    5\n
    "},{"location":"api/basic_json/end/#version-history","title":"Version history","text":""},{"location":"api/basic_json/end_pos/","title":"nlohmann::basic_json::end_pos","text":"
    #if JSON_DIAGNOSTIC_POSITIONS\nconstexpr std::size_t end_pos() const noexcept;\n#endif\n

    Returns the position immediately following the last character of the JSON string from which the value was parsed from.

    JSON type return value object position after the closing } array position after the closing ] string position after the closing \" number position after the last character boolean position after e null position after l"},{"location":"api/basic_json/end_pos/#return-value","title":"Return value","text":"

    the position of the character following the last character of the given value in the parsed JSON string, if the value was created by the parse function, or std::string::npos if the value was constructed otherwise

    "},{"location":"api/basic_json/end_pos/#exception-safety","title":"Exception safety","text":"

    No-throw guarantee: this member function never throws exceptions.

    "},{"location":"api/basic_json/end_pos/#complexity","title":"Complexity","text":"

    Constant.

    "},{"location":"api/basic_json/end_pos/#notes","title":"Notes","text":"

    Note

    The function is only available if macro JSON_DIAGNOSTIC_POSITIONS has been defined to 1 before including the library header.

    Invalidation

    The returned positions are only valid as long as the JSON value is not changed. The positions are not updated when the JSON value is changed.

    "},{"location":"api/basic_json/end_pos/#examples","title":"Examples","text":"Example 
    #include <iostream>\n\n#define JSON_DIAGNOSTIC_POSITIONS 1\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    std::string json_string = R\"(\n    {\n        \"address\": {\n            \"street\": \"Fake Street\",\n            \"housenumber\": 1\n        }\n    }\n    )\";\n    json j = json::parse(json_string);\n\n    std::cout << \"Root diagnostic positions: \\n\";\n    std::cout << \"\\tstart_pos: \" << j.start_pos() << '\\n';\n    std::cout << \"\\tend_pos:\" << j.end_pos() << \"\\n\";\n    std::cout << \"Original string: \\n\";\n    std::cout << \"{\\n        \\\"address\\\": {\\n            \\\"street\\\": \\\"Fake Street\\\",\\n            \\\"housenumber\\\": 1\\n        }\\n    }\" << \"\\n\";\n    std::cout << \"Parsed string: \\n\";\n    std::cout << json_string.substr(j.start_pos(), j.end_pos() - j.start_pos()) << \"\\n\\n\";\n\n    std::cout << \"address diagnostic positions: \\n\";\n    std::cout << \"\\tstart_pos:\" << j[\"address\"].start_pos() << '\\n';\n    std::cout << \"\\tend_pos:\" << j[\"address\"].end_pos() << \"\\n\\n\";\n    std::cout << \"Original string: \\n\";\n    std::cout << \"{            \\\"street\\\": \\\"Fake Street\\\",\\n            \\\"housenumber\\\": 1\\n        }\" << \"\\n\";\n    std::cout << \"Parsed string: \\n\";\n    std::cout << json_string.substr(j[\"address\"].start_pos(), j[\"address\"].end_pos() - j[\"address\"].start_pos()) << \"\\n\\n\";\n\n    std::cout << \"street diagnostic positions: \\n\";\n    std::cout << \"\\tstart_pos:\" << j[\"address\"][\"street\"].start_pos() << '\\n';\n    std::cout << \"\\tend_pos:\" << j[\"address\"][\"street\"].end_pos() << \"\\n\\n\";\n    std::cout << \"Original string: \\n\";\n    std::cout << \"\\\"Fake Street\\\"\" << \"\\n\";\n    std::cout << \"Parsed string: \\n\";\n    std::cout << json_string.substr(j[\"address\"][\"street\"].start_pos(), j[\"address\"][\"street\"].end_pos() - j[\"address\"][\"street\"].start_pos()) << \"\\n\\n\";\n\n    std::cout << \"housenumber diagnostic positions: \\n\";\n    std::cout << \"\\tstart_pos:\" << j[\"address\"][\"housenumber\"].start_pos() << '\\n';\n    std::cout << \"\\tend_pos:\" << j[\"address\"][\"housenumber\"].end_pos() << \"\\n\\n\";\n    std::cout << \"Original string: \\n\";\n    std::cout << \"1\" << \"\\n\";\n    std::cout << \"Parsed string: \\n\";\n    std::cout << json_string.substr(j[\"address\"][\"housenumber\"].start_pos(), j[\"address\"][\"housenumber\"].end_pos() - j[\"address\"][\"housenumber\"].start_pos()) << \"\\n\\n\";\n}\n

    Output:

    Root diagnostic positions: \n    start_pos: 5\n    end_pos:109\nOriginal string: \n{\n        \"address\": {\n            \"street\": \"Fake Street\",\n            \"housenumber\": 1\n        }\n    }\nParsed string: \n{\n        \"address\": {\n            \"street\": \"Fake Street\",\n            \"housenumber\": 1\n        }\n    }\n\naddress diagnostic positions: \n    start_pos:26\n    end_pos:103\n\nOriginal string: \n{            \"street\": \"Fake Street\",\n            \"housenumber\": 1\n        }\nParsed string: \n{\n            \"street\": \"Fake Street\",\n            \"housenumber\": 1\n        }\n\nstreet diagnostic positions: \n    start_pos:50\n    end_pos:63\n\nOriginal string: \n\"Fake Street\"\nParsed string: \n\"Fake Street\"\n\nhousenumber diagnostic positions: \n    start_pos:92\n    end_pos:93\n\nOriginal string: \n1\nParsed string: \n1\n

    The output shows the start/end positions of all the objects and fields in the JSON string.

    "},{"location":"api/basic_json/end_pos/#see-also","title":"See also","text":""},{"location":"api/basic_json/end_pos/#version-history","title":"Version history","text":""},{"location":"api/basic_json/erase/","title":"nlohmann::basic_json::erase","text":"
    // (1)\niterator erase(iterator pos);\nconst_iterator erase(const_iterator pos);\n\n// (2)\niterator erase(iterator first, iterator last);\nconst_iterator erase(const_iterator first, const_iterator last);\n\n// (3)\nsize_type erase(const typename object_t::key_type& key);\n\n// (4)\ntemplate<typename KeyType>\nsize_type erase(KeyType&& key);\n\n// (5)\nvoid erase(const size_type idx);\n

    1. Removes an element from a JSON value specified by iterator pos. The iterator pos must be valid and dereferenceable. Thus, the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos.

      If called on a primitive type other than null, the resulting JSON value will be null.

    2. Remove an element range specified by [first; last) from a JSON value. The iterator first does not need to be dereferenceable if first == last: erasing an empty range is a no-op.

      If called on a primitive type other than null, the resulting JSON value will be null.

    3. Removes an element from a JSON object by key.

    4. See 3. This overload is only available if KeyType is comparable with typename object_t::key_type and typename object_comparator_t::is_transparent denotes a type.

    5. Removes an element from a JSON array by index.

    "},{"location":"api/basic_json/erase/#template-parameters","title":"Template parameters","text":"KeyType A type for an object key other than json_pointer that is comparable with string_t using object_comparator_t. This can also be a string view (C++17)."},{"location":"api/basic_json/erase/#parameters","title":"Parameters","text":"pos (in) iterator to the element to remove first (in) iterator to the beginning of the range to remove last (in) iterator past the end of the range to remove key (in) object key of the elements to remove idx (in) array index of the element to remove"},{"location":"api/basic_json/erase/#return-value","title":"Return value","text":"
    1. Iterator following the last removed element. If the iterator pos refers to the last element, the end() iterator is returned.
    2. Iterator following the last removed element. If the iterator last refers to the last element, the end() iterator is returned.
    3. Number of elements removed. If ObjectType is the default std::map type, the return value will always be 0 (key was not found) or 1 (key was found).
    4. See 3.
    5. (none)
    "},{"location":"api/basic_json/erase/#exception-safety","title":"Exception safety","text":"

    Strong exception safety: if an exception occurs, the original value stays intact.

    "},{"location":"api/basic_json/erase/#exceptions","title":"Exceptions","text":"
    1. The function can throw the following exceptions:
      • Throws type_error.307 if called on a null value; example: \"cannot use erase() with null\"
      • Throws invalid_iterator.202 if called on an iterator which does not belong to the current JSON value; example: \"iterator does not fit current value\"
      • Throws invalid_iterator.205 if called on a primitive type with invalid iterator (i.e., any iterator which is not begin()); example: \"iterator out of range\"
    2. The function can throw the following exceptions:
      • Throws type_error.307 if called on a null value; example: \"cannot use erase() with null\"
      • Throws invalid_iterator.203 if called on iterators which does not belong to the current JSON value; example: \"iterators do not fit current value\"
      • Throws invalid_iterator.204 if called on a primitive type with invalid iterators (i.e., if first != begin() and last != end()); example: \"iterators out of range\"
    3. The function can throw the following exceptions:
      • Throws type_error.307 when called on a type other than JSON object; example: \"cannot use erase() with null\"
    4. See 3.
    5. The function can throw the following exceptions:
      • Throws type_error.307 when called on a type other than JSON array; example: \"cannot use erase() with null\"
      • Throws out_of_range.401 when idx >= size(); example: \"array index 17 is out of range\"
    "},{"location":"api/basic_json/erase/#complexity","title":"Complexity","text":"
    1. The complexity depends on the type:
      • objects: amortized constant
      • arrays: linear in distance between pos and the end of the container
      • strings and binary: linear in the length of the member
      • other types: constant
    2. The complexity depends on the type:
      • objects: log(size()) + std::distance(first, last)
      • arrays: linear in the distance between first and last, plus linear in the distance between last and end of the container
      • strings and binary: linear in the length of the member
      • other types: constant
    3. log(size()) + count(key)
    4. log(size()) + count(key)
    5. Linear in distance between idx and the end of the container.
    "},{"location":"api/basic_json/erase/#notes","title":"Notes","text":"
    1. Invalidates iterators and references at or after the point of the erase, including the end() iterator.
    2. (none)
    3. References and iterators to the erased elements are invalidated. Other references and iterators are not affected.
    4. See 3.
    5. (none)
    "},{"location":"api/basic_json/erase/#examples","title":"Examples","text":"Example: (1) remove element given an iterator

    The example shows the effect of erase() for different JSON types using an iterator.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_boolean = true;\n    json j_number_integer = 17;\n    json j_number_float = 23.42;\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_array = {1, 2, 4, 8, 16};\n    json j_string = \"Hello, world\";\n\n    // call erase()\n    j_boolean.erase(j_boolean.begin());\n    j_number_integer.erase(j_number_integer.begin());\n    j_number_float.erase(j_number_float.begin());\n    j_object.erase(j_object.find(\"two\"));\n    j_array.erase(j_array.begin() + 2);\n    j_string.erase(j_string.begin());\n\n    // print values\n    std::cout << j_boolean << '\\n';\n    std::cout << j_number_integer << '\\n';\n    std::cout << j_number_float << '\\n';\n    std::cout << j_object << '\\n';\n    std::cout << j_array << '\\n';\n    std::cout << j_string << '\\n';\n}\n

    Output:

    null\nnull\nnull\n{\"one\":1}\n[1,2,8,16]\nnull\n
    Example: (2) remove elements given an iterator range

    The example shows the effect of erase() for different JSON types using an iterator range.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON values\n    json j_boolean = true;\n    json j_number_integer = 17;\n    json j_number_float = 23.42;\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n    json j_array = {1, 2, 4, 8, 16};\n    json j_string = \"Hello, world\";\n\n    // call erase()\n    j_boolean.erase(j_boolean.begin(), j_boolean.end());\n    j_number_integer.erase(j_number_integer.begin(), j_number_integer.end());\n    j_number_float.erase(j_number_float.begin(), j_number_float.end());\n    j_object.erase(j_object.find(\"two\"), j_object.end());\n    j_array.erase(j_array.begin() + 1, j_array.begin() + 3);\n    j_string.erase(j_string.begin(), j_string.end());\n\n    // print values\n    std::cout << j_boolean << '\\n';\n    std::cout << j_number_integer << '\\n';\n    std::cout << j_number_float << '\\n';\n    std::cout << j_object << '\\n';\n    std::cout << j_array << '\\n';\n    std::cout << j_string << '\\n';\n}\n

    Output:

    null\nnull\nnull\n{\"one\":1}\n[1,8,16]\nnull\n
    Example: (3) remove element from a JSON object given a key

    The example shows the effect of erase() for different JSON types using an object key.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n\n    // call erase()\n    auto count_one = j_object.erase(\"one\");\n    auto count_three = j_object.erase(\"three\");\n\n    // print values\n    std::cout << j_object << '\\n';\n    std::cout << count_one << \" \" << count_three << '\\n';\n}\n

    Output:

    {\"two\":2}\n1 0\n
    Example: (4) remove element from a JSON object given a key using string_view

    The example shows the effect of erase() for different JSON types using an object key.

    #include <iostream>\n#include <string_view>\n#include <nlohmann/json.hpp>\n\nusing namespace std::string_view_literals;\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n\n    // call erase()\n    auto count_one = j_object.erase(\"one\"sv);\n    auto count_three = j_object.erase(\"three\"sv);\n\n    // print values\n    std::cout << j_object << '\\n';\n    std::cout << count_one << \" \" << count_three << '\\n';\n}\n

    Output:

    {\"two\":2}\n1 0\n
    Example: (5) remove element from a JSON array given an index

    The example shows the effect of erase() using an array index.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON array\n    json j_array = {0, 1, 2, 3, 4, 5};\n\n    // call erase()\n    j_array.erase(2);\n\n    // print values\n    std::cout << j_array << '\\n';\n}\n

    Output:

    [0,1,3,4,5]\n
    "},{"location":"api/basic_json/erase/#see-also","title":"See also","text":""},{"location":"api/basic_json/erase/#version-history","title":"Version history","text":"
    1. Added in version 1.0.0. Added support for binary types in version 3.8.0.
    2. Added in version 1.0.0. Added support for binary types in version 3.8.0.
    3. Added in version 1.0.0.
    4. Added in version 3.11.0.
    5. Added in version 1.0.0.
    "},{"location":"api/basic_json/error_handler_t/","title":"nlohmann::basic_json::error_handler_t","text":"
    enum class error_handler_t {\n    strict,\n    replace,\n    ignore\n};\n

    This enumeration is used in the dump function to choose how to treat decoding errors while serializing a basic_json value. Three values are differentiated:

    strict throw a type_error exception in case of invalid UTF-8 replace replace invalid UTF-8 sequences with U+FFFD (\ufffd REPLACEMENT CHARACTER) ignore ignore invalid UTF-8 sequences; all valid bytes are copied to the output unchanged, and invalid bytes are dropped"},{"location":"api/basic_json/error_handler_t/#examples","title":"Examples","text":"Example

    The example below shows how the different values of the error_handler_t influence the behavior of dump when reading serializing an invalid UTF-8 sequence.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON value with invalid UTF-8 byte sequence\n    json j_invalid = \"\u00e4\\xA9\u00fc\";\n    try\n    {\n        std::cout << j_invalid.dump() << std::endl;\n    }\n    catch (const json::type_error& e)\n    {\n        std::cout << e.what() << std::endl;\n    }\n\n    std::cout << \"string with replaced invalid characters: \"\n              << j_invalid.dump(-1, ' ', false, json::error_handler_t::replace)\n              << \"\\nstring with ignored invalid characters: \"\n              << j_invalid.dump(-1, ' ', false, json::error_handler_t::ignore)\n              << '\\n';\n}\n

    Output:

    [json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9\nstring with replaced invalid characters: \"\u00e4\ufffd\u00fc\"\nstring with ignored invalid characters: \"\u00e4\u00fc\"\n
    "},{"location":"api/basic_json/error_handler_t/#version-history","title":"Version history","text":""},{"location":"api/basic_json/exception/","title":"nlohmann::basic_json::exception","text":"
    class exception : public std::exception;\n

    This class is an extension of std::exception objects with a member id for exception ids. It is used as the base class for all exceptions thrown by the basic_json class. This class can hence be used as \"wildcard\" to catch exceptions, see example below.

    classDiagram\n  direction LR\n\n    class std_exception [\"std::exception\"] {\n        <<interface>>\n    }\n\n    class json_exception [\"basic_json::exception\"] {\n        +const int id\n        +const char* what() const\n    }\n\n    class json_parse_error [\"basic_json::parse_error\"] {\n        +const std::size_t byte\n    }\n\n    class json_invalid_iterator [\"basic_json::invalid_iterator\"]\n    class json_type_error [\"basic_json::type_error\"]\n    class json_out_of_range [\"basic_json::out_of_range\"]\n    class json_other_error [\"basic_json::other_error\"]\n\n    std_exception <|-- json_exception\n    json_exception <|-- json_parse_error\n    json_exception <|-- json_invalid_iterator\n    json_exception <|-- json_type_error\n    json_exception <|-- json_out_of_range\n    json_exception <|-- json_other_error\n\n    style json_exception fill:#CCCCFF

    Subclasses:

    "},{"location":"api/basic_json/exception/#member-functions","title":"Member functions","text":""},{"location":"api/basic_json/exception/#member-variables","title":"Member variables","text":""},{"location":"api/basic_json/exception/#notes","title":"Notes","text":"

    To have nothrow-copy-constructible exceptions, we internally use std::runtime_error which can cope with arbitrary-length error messages. Intermediate strings are built with static functions and then passed to the actual constructor.

    "},{"location":"api/basic_json/exception/#examples","title":"Examples","text":"Example

    The following code shows how arbitrary library exceptions can be caught.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    try\n    {\n        // calling at() for a non-existing key\n        json j = {{\"foo\", \"bar\"}};\n        json k = j.at(\"non-existing\");\n    }\n    catch (const json::exception& e)\n    {\n        // output exception information\n        std::cout << \"message: \" << e.what() << '\\n'\n                  << \"exception id: \" << e.id << std::endl;\n    }\n}\n

    Output:

    message: [json.exception.out_of_range.403] key 'non-existing' not found\nexception id: 403\n
    "},{"location":"api/basic_json/exception/#see-also","title":"See also","text":"

    List of exceptions

    "},{"location":"api/basic_json/exception/#version-history","title":"Version history","text":""},{"location":"api/basic_json/find/","title":"nlohmann::basic_json::find","text":"
    // (1)\niterator find(const typename object_t::key_type& key);\nconst_iterator find(const typename object_t::key_type& key) const;\n\n// (2)\ntemplate<typename KeyType>\niterator find(KeyType&& key);\ntemplate<typename KeyType>\nconst_iterator find(KeyType&& key) const;\n
    1. Finds an element in a JSON object with a key equivalent to key. If the element is not found or the JSON value is not an object, end() is returned.
    2. See 1. This overload is only available if KeyType is comparable with typename object_t::key_type and typename object_comparator_t::is_transparent denotes a type.
    "},{"location":"api/basic_json/find/#template-parameters","title":"Template parameters","text":"KeyType A type for an object key other than json_pointer that is comparable with string_t using object_comparator_t. This can also be a string view (C++17)."},{"location":"api/basic_json/find/#parameters","title":"Parameters","text":"key (in) key value of the element to search for."},{"location":"api/basic_json/find/#return-value","title":"Return value","text":"

    Iterator to an element with a key equivalent to key. If no such element is found or the JSON value is not an object, a past-the-end iterator (see end()) is returned.

    "},{"location":"api/basic_json/find/#exception-safety","title":"Exception safety","text":"

    Strong exception safety: if an exception occurs, the original value stays intact.

    "},{"location":"api/basic_json/find/#complexity","title":"Complexity","text":"

    Logarithmic in the size of the JSON object.

    "},{"location":"api/basic_json/find/#notes","title":"Notes","text":"

    This method always returns end() when executed on a JSON type that is not an object.

    "},{"location":"api/basic_json/find/#examples","title":"Examples","text":"Example: (1) find object element by key

    The example shows how find() is used.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n\n    // call find\n    auto it_two = j_object.find(\"two\");\n    auto it_three = j_object.find(\"three\");\n\n    // print values\n    std::cout << std::boolalpha;\n    std::cout << \"\\\"two\\\" was found: \" << (it_two != j_object.end()) << '\\n';\n    std::cout << \"value at key \\\"two\\\": \" << *it_two << '\\n';\n    std::cout << \"\\\"three\\\" was found: \" << (it_three != j_object.end()) << '\\n';\n}\n

    Output:

    \"two\" was found: true\nvalue at key \"two\": 2\n\"three\" was found: false\n
    Example: (2) find object element by key using string_view

    The example shows how find() is used.

    #include <iostream>\n#include <string_view>\n#include <nlohmann/json.hpp>\n\nusing namespace std::string_view_literals;\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j_object = {{\"one\", 1}, {\"two\", 2}};\n\n    // call find\n    auto it_two = j_object.find(\"two\"sv);\n    auto it_three = j_object.find(\"three\"sv);\n\n    // print values\n    std::cout << std::boolalpha;\n    std::cout << \"\\\"two\\\" was found: \" << (it_two != j_object.end()) << '\\n';\n    std::cout << \"value at key \\\"two\\\": \" << *it_two << '\\n';\n    std::cout << \"\\\"three\\\" was found: \" << (it_three != j_object.end()) << '\\n';\n}\n

    Output:

    \"two\" was found: true\nvalue at key \"two\": 2\n\"three\" was found: false\n
    "},{"location":"api/basic_json/find/#see-also","title":"See also","text":""},{"location":"api/basic_json/find/#version-history","title":"Version history","text":"
    1. Added in version 3.11.0.
    2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.
    "},{"location":"api/basic_json/flatten/","title":"nlohmann::basic_json::flatten","text":"
    basic_json flatten() const;\n

    The function creates a JSON object whose keys are JSON pointers (see RFC 6901) and whose values are all primitive (see is_primitive() for more information). The original JSON value can be restored using the unflatten() function.

    "},{"location":"api/basic_json/flatten/#return-value","title":"Return value","text":"

    an object that maps JSON pointers to primitive values

    "},{"location":"api/basic_json/flatten/#exception-safety","title":"Exception safety","text":"

    Strong exception safety: if an exception occurs, the original value stays intact.

    "},{"location":"api/basic_json/flatten/#complexity","title":"Complexity","text":"

    Linear in the size of the JSON value.

    "},{"location":"api/basic_json/flatten/#notes","title":"Notes","text":"

    Empty objects and arrays are flattened to null and will not be reconstructed correctly by the unflatten() function.

    "},{"location":"api/basic_json/flatten/#examples","title":"Examples","text":"Example

    The following code shows how a JSON object is flattened to an object whose keys consist of JSON pointers.

    #include <iostream>\n#include <iomanip>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create JSON value\n    json j =\n    {\n        {\"pi\", 3.141},\n        {\"happy\", true},\n        {\"name\", \"Niels\"},\n        {\"nothing\", nullptr},\n        {\n            \"answer\", {\n                {\"everything\", 42}\n            }\n        },\n        {\"list\", {1, 0, 2}},\n        {\n            \"object\", {\n                {\"currency\", \"USD\"},\n                {\"value\", 42.99}\n            }\n        }\n    };\n\n    // call flatten()\n    std::cout << std::setw(4) << j.flatten() << '\\n';\n}\n

    Output:

    {\n    \"/answer/everything\": 42,\n    \"/happy\": true,\n    \"/list/0\": 1,\n    \"/list/1\": 0,\n    \"/list/2\": 2,\n    \"/name\": \"Niels\",\n    \"/nothing\": null,\n    \"/object/currency\": \"USD\",\n    \"/object/value\": 42.99,\n    \"/pi\": 3.141\n}\n
    "},{"location":"api/basic_json/flatten/#see-also","title":"See also","text":""},{"location":"api/basic_json/flatten/#version-history","title":"Version history","text":""},{"location":"api/basic_json/format_as/","title":"format_as(basic_json)","text":"
    template <typename BasicJsonType>\nstd::string format_as(const BasicJsonType& j);\n

    This function implements the format_as customization point used by the {fmt} library (fmtlib). It has no dependency on any fmt header and no effect at all unless a caller's translation unit also includes fmt and calls fmt::format/fmt::print on a JSON value.

    "},{"location":"api/basic_json/format_as/#template-parameters","title":"Template parameters","text":"BasicJsonType a specialization of basic_json"},{"location":"api/basic_json/format_as/#return-value","title":"Return value","text":"

    string containing the serialization of the JSON value (same as dump())

    "},{"location":"api/basic_json/format_as/#exception-safety","title":"Exception safety","text":"

    Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

    "},{"location":"api/basic_json/format_as/#exceptions","title":"Exceptions","text":"

    Throws type_error.316 if a string stored inside the JSON value is not UTF-8 encoded

    "},{"location":"api/basic_json/format_as/#complexity","title":"Complexity","text":"

    Linear.

    "},{"location":"api/basic_json/format_as/#possible-implementation","title":"Possible implementation","text":"
    template <typename BasicJsonType>\nstd::string format_as(const BasicJsonType& j)\n{\n    return j.dump();\n}\n
    "},{"location":"api/basic_json/format_as/#notes","title":"Notes","text":"

    Version-dependent effect on fmt

    fmt only picks up a format_as overload that returns a std::string in fmt 10.0.0 through 11.0.2. Starting with fmt 11.1.0, fmt restricts automatic format_as pickup to overloads that return an arithmetic type, so this function has no effect there (it is simply unused, not a compile error).

    If you use fmt >= 11.1.0, or want the same pretty-print spec support that std::formatter<basic_json> has (\"{:#}\", a width to set the indent such as \"{:2}\"/\"{:#2}\", and fill-and-align to pick the indent character such as \"{:.>#}\"), define your own fmt::formatter specialization mirroring the same logic:

    template <>\nstruct fmt::formatter<nlohmann::json>\n{\n    // -1 means compact output (dump()); any value >= 0 means pretty-printed\n    // output with that many spaces (or indent_char) per level.\n    int indent = -1;\n    char indent_char = ' ';\n\n    constexpr auto parse(format_parse_context& ctx) -> format_parse_context::iterator\n    {\n        auto it = ctx.begin();\n        const auto end = ctx.end();\n        constexpr auto is_align = [](char c)\n        {\n            return c == '<' || c == '>' || c == '^';\n        };\n\n        // [[fill] align] - repurposed here to pick a custom indent character\n        if (it != end && it + 1 != end && is_align(it[1]))\n        {\n            indent_char = *it;\n            it += 2;\n        }\n        else if (it != end && is_align(*it))\n        {\n            ++it;\n        }\n\n        // ['#'] - \"alternate form\", used here to request pretty-printing with a\n        // default indent of 4 (overridden by an explicit width below, if given)\n        if (it != end && *it == '#')\n        {\n            indent = 4;\n            ++it;\n        }\n\n        // [width] - repurposed here to pick the indent size; a width without '#'\n        // implies pretty-printing since an indent otherwise has no meaning\n        if (it != end && *it >= '1' && *it <= '9')\n        {\n            indent = 0;\n            while (it != end && *it >= '0' && *it <= '9')\n            {\n                indent = (indent * 10) + (*it - '0');\n                ++it;\n            }\n        }\n\n        if (it != end && *it != '}')\n        {\n            throw fmt::format_error(\"invalid format args for nlohmann::json\");\n        }\n\n        return it;\n    }\n\n    auto format(const nlohmann::json& j, format_context& ctx) const\n    {\n        const auto dumped = j.dump(indent, indent_char);\n        return fmt::format_to(ctx.out(), \"{}\", dumped);\n    }\n};\n

    This recipe isn't shipped by the library itself, since doing so would make fmt a build dependency (see the FAQ entry on using JSON values with std::format or fmt for more background) \u2014 but it is compiled and exercised against a real, current fmt release as part of the library's own test suite (tests/fmt_formatter, via CMake FetchContent), so it's kept in sync with std::formatter<basic_json> and verified to actually work, not just illustrative.

    "},{"location":"api/basic_json/format_as/#examples","title":"Examples","text":"Example

    The following code shows how the library's format_as() function integrates with fmt::format, allowing argument-dependent lookup.

    #include <iostream>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON value\n    json j = {{\"one\", 1}, {\"two\", 2}};\n\n    // format_as() is found via argument-dependent lookup, the same way\n    // fmt::format/fmt::print would find it\n    auto j_str = format_as(j);\n\n    std::cout << j_str << std::endl;\n}\n

    Output:

    {\"one\":1,\"two\":2}\n
    "},{"location":"api/basic_json/format_as/#see-also","title":"See also","text":"