5352856f04
* Add key_compare member to ordered_map
* Replace == with key_compare in ordered_map
* Expose the actual comparison function used by object_t
nlohmann::ordered_map uses a different comparison function than the one
provided via template parameter.
* Introduce a type trait to detect if object_t has a key_compare member.
* Rename object_comparator_t to default_object_comparator_t.
* Add object_comparator_t to be conditionally defined as
object_t::key_compare, if available, or default_object_comparator_t
otherwise.
* Update the documentation accordingly.
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Add type traits to check if a type is usable as object key
Add type trait to check:
* if a type is a specialization of a template.
* if a type is a json_pointer.
* if a type is a basic_json::{const_,}iterator.
* if two types are comparable using a given comparison functor.
* if a type is comparable to basic_json::object_t::key_type.
* if a type has a member type is_transparent.
* if a type is usable as object key.
* if a type has an erase() function accepting a given KeyType.
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Rework basic_json element access to accept more key types
Rework basic_json element access member functions and operators to
accept any type that meets the requirements defined by type trait
detail::is_usable_as_key_type.
Member functions and operators:
* at()
* operator[]
* value()
* erase()
* find()
* count()
* contains()
Update documentation to reflect these changes.
Add unit tests to excercise the new functions using std::string_view.
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
78 lines
1.6 KiB
Markdown
78 lines
1.6 KiB
Markdown
# <small>nlohmann::</small>ordered_map
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```cpp
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template<class Key, class T, class IgnoredLess = std::less<Key>,
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class Allocator = std::allocator<std::pair<const Key, T>>>
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struct ordered_map : std::vector<std::pair<const Key, T>, Allocator>;
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```
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A minimal map-like container that preserves insertion order for use within [`nlohmann::ordered_json`](ordered_json.md)
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(`nlohmann::basic_json<ordered_map>`).
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## Template parameters
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`Key`
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: key type
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`T`
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: mapped type
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`IgnoredLess`
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: comparison function (ignored and only added to ensure compatibility with `#!cpp std::map`)
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`Allocator`
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: allocator type
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## Member types
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- **key_type** - key type (`Key`)
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- **mapped_type** - mapped type (`T`)
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- **Container** - base container type (`#!cpp std::vector<std::pair<const Key, T>, Allocator>`)
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- **iterator**
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- **const_iterator**
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- **size_type**
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- **value_type**
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- **key_compare** - key comparison function
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```cpp
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std::equal_to<Key> // until C++14
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std::equal_to<> // since C++14
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```
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## Member functions
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- (constructor)
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- (destructor)
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- **emplace**
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- **operator\[\]**
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- **at**
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- **erase**
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- **count**
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- **find**
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- **insert**
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## Examples
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??? example
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The example shows the different behavior of `std::map` and `nlohmann::ordered_map`.
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```cpp
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--8<-- "examples/ordered_map.cpp"
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```
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Output:
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```json
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--8<-- "examples/ordered_map.output"
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```
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## See also
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- [ordered_json](ordered_json.md)
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## Version history
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- Added in version 3.9.0 to implement [`nlohmann::ordered_json`](ordered_json.md).
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- Added **key_compare** member in version 3.11.0.
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