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@@ -19,11 +19,11 @@ For the types below, the conversion works directly on the flat index — no `Bas
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- `std::vector<U, A>` of the types above — from an array, element by element, each converted with `get<U>()`; `std::vector<basic_json_view>` keeps a view of every element instead of a value
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- `std::map<K, basic_json_view, C, A>` and `std::unordered_map<K, basic_json_view, H, E, A>`, if `K` is constructible from a `(const char*, std::size_t)` pair — views of the members of an object; with a repeated key, the view of the *last* member is kept, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) keeps its value
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A default-constructible `T` whose `from_json()` accepts views reads the view directly as well, without building a `BasicJsonType` value. This covers the library's own conversions of the standard library types — all other `std::vector`s, `std::map`/`std::unordered_map` (also with other key types), `std::list`, `std::deque`, `std::set`, `std::forward_list`, `std::valarray`, `std::array`, C arrays, `std::pair`, `std::tuple`, `std::optional`, enumerations, `std::filesystem::path`, ... -- which give the same values as `materialize().get<T>()` (from an object, a repeated key keeps the *last* value, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) does), as well as the types of the [`NLOHMANN_DEFINE_TYPE_*`](https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/index.md) and [`NLOHMANN_DEFINE_DERIVED_TYPE_*`](https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/index.md) macros and the enumerations of [`NLOHMANN_JSON_SERIALIZE_ENUM`](https://json.nlohmann.me/api/macros/nlohmann_json_serialize_enum/index.md), and any `from_json()` constrained to accept views, e.g. with [`is_json_view`](https://json.nlohmann.me/api/is_json_view/index.md). A `from_json()` that also accepts types that are no JSON values at all, such as the unconstrained `template<typename BasicJsonType> void from_json(const BasicJsonType&,T&)` of [arbitrary type conversions](https://json.nlohmann.me/features/arbitrary_types/index.md), is not called with a view: it may use `BasicJsonType` functions a view does not have. See [Writing generic code](https://json.nlohmann.me/features/json_view/#writing-generic-code).
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A default-constructible `T` whose `from_json()` accepts views reads the view directly as well, without building a `BasicJsonType` value. This covers the library's own conversions of the standard library types — all other `std::vector`s, `std::map`/`std::unordered_map` (also with other key types), `std::list`, `std::deque`, `std::set`, `std::forward_list`, `std::valarray`, `std::array`, C arrays, `std::pair`, `std::tuple`, `std::optional`, enumerations, `std::filesystem::path`, ... -- which give the same values as `materialize().get<T>()` (from an object, a repeated key keeps the *last* value, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) does), as well as the types of the [`NLOHMANN_DEFINE_TYPE_*`](https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/index.md) and [`NLOHMANN_DEFINE_DERIVED_TYPE_*`](https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/index.md) macros and the enumerations of [`NLOHMANN_JSON_SERIALIZE_ENUM`](https://json.nlohmann.me/api/macros/nlohmann_json_serialize_enum/index.md), and any `from_json()` constrained to accept views, e.g. with [`is_json_view`](https://json.nlohmann.me/api/is_json_view/index.md). A `from_json()` that also accepts types that are no JSON values at all, such as the unconstrained `template<typename BasicJsonType> void from_json(const BasicJsonType&,T&)` of [arbitrary type conversions](https://json.nlohmann.me/features/arbitrary_types/index.md), is not called with a view: it may use `BasicJsonType` functions a view does not have. See [Writing generic code](https://json.nlohmann.me/features/json_view/generic_code/index.md).
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Duplicate keys
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Such a `from_json()` looks members up in the view, where a repeated key finds the **first** member, while `materialize().get<T>()` sees the **last** one, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) keeps it: for `{"x":1,"x":2}`, `get<point>()` reads `x == 1`. See [Duplicate keys](https://json.nlohmann.me/features/json_view/#duplicate-keys).
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Such a `from_json()` looks members up in the view, where a repeated key finds the **first** member, while `materialize().get<T>()` sees the **last** one, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) keeps it: for `{"x":1,"x":2}`, `get<point>()` reads `x == 1`. See [Duplicate keys](https://json.nlohmann.me/features/json_view/differences/#duplicate-keys).
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Every other `T` — user types whose `from_json()` is written for `BasicJsonType` only, types without a default constructor, `std::tuple`s holding references, ... — is converted by `materialize().get<T>()`: the subtree is built into a real `BasicJsonType` value first (as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) would), and converted from there exactly as [`BasicJsonType::get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md) would convert it.
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@@ -152,7 +152,7 @@ Berlin 10115
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- [`number_token`](https://json.nlohmann.me/api/basic_json_view/number_token/index.md) - a number's token text, without a copy
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- [`materialize`](https://json.nlohmann.me/api/basic_json_view/materialize/index.md) - build the `BasicJsonType` value of this subtree
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- [`BasicJsonType::get`](https://json.nlohmann.me/api/basic_json/get/index.md) - the corresponding function of `basic_json`
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- [Zero-copy JSON views](https://json.nlohmann.me/features/json_view/#getting-values-out-without-copying) - which conversions avoid building a basic_json value
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- [Zero-copy JSON views](https://json.nlohmann.me/features/json_view/reading/#getting-values-out-without-copying) - which conversions avoid building a basic_json value
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## Version history
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