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Niels Lohmann
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* 📡 Fix documentation gaps for 3.13.0 release (todos 138-142) - Todo 138: Add "Known issues" section to modules.md with compiler-specific troubleshooting (GCC redefinition, MSVC symbol export). Add pointer note to quality_assurance.md. - Todo 139: Document CBOR/MessagePack half-precision float encoding for NaN/Infinity (0xF9/0xCA with exact byte sequences). Explain pre-3.13.0 double-precision bug mechanism without issue citations. - Todo 140: Document CBOR negative-integer-overflow rejection (parse_error.112) for magnitudes exceeding int64_t range (already implemented in rev 1). - Todo 141: Update version history in value.md and operator[].md with behavior-change details, removing issue citations per citation policy (prose is self-contained). - Todo 142: Global sed replace of 3.12.x → 3.13.0 placeholder across all 20 documentation files. Revision 2 incorporates feedback to reduce changelog-like issue citations. Only citations that add unique troubleshooting value are retained (#5103 for GCC workaround, #3970 for MSVC symbol export). "Known issues" section follows PR #5252's visual pattern (info admonition with bold-bullet format). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * 📡 Document integer type selection, type_name() invalid value, and std::optional get() fix - number_handling.md: clarify that positive/negative integers select unsigned/signed storage based on the leading minus sign (todo 143). - type_name.md: document the new "invalid" return value for corrupted JSON values (todo 145). - get.md: note that get<std::optional<T>>() was unreachable in every configuration prior to 3.13.0 due to an internal macro-guard bug, unrelated to JSON_USE_IMPLICIT_CONVERSIONS's actual effect (todo 144). Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
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nlohmann::operator""_json
json operator ""_json(const char* s, std::size_t n);
json operator ""_json(const char8_t* s, std::size_t n); // since C++20
This operator implements a user-defined string literal for JSON objects. It can be used by adding #!cpp _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;
using namespace nlohmann::literals;
using namespace nlohmann::json_literals;
using namespace nlohmann::literals::json_literals;
using namespace nlohmann;
This is suggested to ease migration to the next major version release of the library. See
JSON_USE_GLOBAL_UDLS for details.
Parameters
s(in)- a string representation of a JSON object
n(in)- length of string
s
Return value
json value parsed from s
Exceptions
The function can throw anything that parse(s, s+n) would throw.
Complexity
Linear.
Examples
??? example
The following code shows how to create JSON values from string literals.
```cpp
--8<-- "examples/operator_literal_json.cpp"
```
Output:
```json
--8<-- "examples/operator_literal_json.output"
```
See also
- Creating JSON values - the article on creating JSON values
Version history
- Added in version 1.0.0.
- Moved to namespace
nlohmann::literals::json_literalsin 3.11.0. - Added
char8_t*overload in 3.13.0.