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doc/reference.md
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doc/reference.md
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# Reference
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* [`enum_cast` obtains enum value from string or integer.](#enum_cast)
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* [`enum_value` returns enum value at specified index.](#enum_value)
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* [`enum_values` obtains enum value sequence.](#enum_values)
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* [`enum_count` returns number of enum values.](#enum_count)
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* [`enum_integer` obtains integer value from enum value.](#enum_integer)
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* [`enum_name` returns string name from enum value.](#enum_name)
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* [`enum_names` obtains string enum name sequence.](#enum_names)
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* [`enum_entries` obtains pair (value enum, string enum name) sequence.](#enum_entries)
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* [`enum_index` obtains index in enum value sequence from enum value.](#enum_index)
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* [`is_unscoped_enum` checks whether type is an Unscoped enumeration.](#is_unscoped_enum)
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* [`is_scoped_enum` checks whether type is an Scoped enumeration.](#is_scoped_enum)
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* [`underlying_type` improved UB-free "SFINAE-friendly" std::underlying_type.](#underlying_type)
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* [`ostream_operators` ostream operators for enums.](#ostream_operators)
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* [`bitwise_operators` bitwise operators for enums.](#bitwise_operators)
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# Synopsis
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* Before use, read the [limitations](limitations.md) of functionality.
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* To check is magic_enum supported compiler use macro `MAGIC_ENUM_SUPPORTED` or constexpr constant `magic_enum::is_magic_enum_supported`.
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## `enum_cast`
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```cpp
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template <typename E>
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constexpr optional<E> enum_cast(string_view value) noexcept;
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template <typename E>
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constexpr optional<E> enum_cast(underlying_type_t<E> value) noexcept;
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```
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* Obtains enum value from string or integer.
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* Returns `std::optional<E>`, using `has_value()` to check contains enum value and `value()` to get the enum value.
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* If argument does not enum value, returns empty `std::optional`.
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* Examples
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* String to enum value.
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```cpp
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std::string color_name{"GREEN"};
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auto color = magic_enum::enum_cast<Color>(color_name);
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if (color.has_value()) {
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// color.value() -> Color::GREEN
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}
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```
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* Integer to enum value.
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```cpp
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int color_integer = 2;
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auto color = magic_enum::enum_cast<Color>(color_integer);
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if (colo.has_value()) {
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// color.value() -> Color::RED
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}
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```
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## `enum_value`
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```cpp
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template <typename E>
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constexpr E enum_value(std::size_t index) noexcept;
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```
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* Returns enum value at specified index.
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* No bounds checking is performed: the behavior is undefined if `index >= number of enum values`.
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* Examples
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```cpp
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int i = 1;
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Color color = magic_enum::enum_value<Color>(i);
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// color -> Color::BLUE
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````
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## `enum_values`
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```cpp
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template <typename E>
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constexpr array<E, N> enum_values() noexcept;
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```
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* Returns `std::array<E, N>` with all enum value where `N = number of enum values`, sorted by enum value.
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* Examples
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```cpp
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constexpr auto colors = magic_enum::enum_values<Color>();
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// colors -> {Color::RED, Color::BLUE, Color::GREEN}
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// colors[0] -> Color::RED
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```
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## `enum_count`
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```cpp
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template <typename E>
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constexpr size_t enum_count() noexcept;
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```
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* Returns number of enum values.
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* Examples
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```cpp
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constexpr std::size_t color_count = magic_enum::enum_count<Color>();
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// color_count -> 3
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```
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## `enum_integer`
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```cpp
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template <typename E>
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constexpr underlying_type_t<E> enum_integer(E value) noexcept;
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```
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* Returns integer value from enum value.
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* Examples
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```cpp
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Color color = Color::RED;
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auto color_integer = magic_enum::enum_integer(color);
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// color -> 2
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```
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## `enum_name`
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```cpp
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template <typename E>
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constexpr std::string_view enum_name(E value) noexcept;
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template <auto V>
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constexpr std::string_view enum_name() noexcept;
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```
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* Returns `std::string_view`. If enum value does not have name, returns empty string.
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* Examples
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* Enum value to string.
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```cpp
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Color color = Color::RED;
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auto color_name = magic_enum::enum_name(color);
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// color_name -> "RED"
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```
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* Static storage enum variable to string.
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This version is much lighter on the compile times and is not restricted to the enum_range [limitation](doc/limitations.md).
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```cpp
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constexpr Color color = Color::BLUE;
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constexpr auto color_name = magic_enum::enum_name<color>();
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// color_name -> "BLUE"
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```
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* `magic_enum::enum_name<value>()` is much lighter on the compile times and is not restricted to the enum_range [limitation](limitation.md).
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## `enum_names`
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```cpp
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template <typename E>
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constexpr array<std::string_view, N> enum_names() noexcept;
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```
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* Returns `std::array<std::string_view, N>` with all string enum name where `N = number of enum values`, sorted by enum value.
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* Examples
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```cpp
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constexpr auto color_names = magic_enum::enum_names<Color>();
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// color_names -> {"RED", "BLUE", "GREEN"}
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// color_names[0] -> "RED"
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```
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## `enum_entries`
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```cpp
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template <typename E>
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constexpr array<std::pair<E, std::string_view>, N> enum_entries() noexcept;
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```
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* Returns `std::array<std::pair<E, std::string_view>, N>` with all `std::pair` (value enum, string enum name) where `N = number of enum values`, sorted by enum value.
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* Examples
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```cpp
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constexpr auto color_entries = magic_enum::enum_entries<Color>();
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// color_entries -> {{Color::RED, "RED"}, {Color::BLUE, "BLUE"}, {Color::GREEN, "GREEN"}}
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// color_entries[0].first -> Color::RED
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// color_entries[0].second -> "RED"
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```
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## `is_unscoped_enum`
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```cpp
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template <typename T>
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struct is_unscoped_enum;
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template <typename T>
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inline constexpr bool is_unscoped_enum_v = is_unscoped_enum<T>::value;
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```
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* Checks whether type is an [Unscoped enumeration](https://en.cppreference.com/w/cpp/language/enum#Unscoped_enumeration).
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* Provides the member constant value which is equal to true, if T is an [Unscoped enumeration](https://en.cppreference.com/w/cpp/language/enum#Unscoped_enumeration) type. Otherwise, value is equal to false.
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* Examples
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```cpp
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magic_enum::is_unscoped_enum<color>::value -> true
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magic_enum::is_unscoped_enum<Direction>::value -> false
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// Helper variable template.
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magic_enum::is_unscoped_enum_v<color> -> true
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```
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## `is_scoped_enum`
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```cpp
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template <typename T>
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struct is_scoped_enum;
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template <typename T>
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inline constexpr bool is_scoped_enum_v = is_scoped_enum<T>::value;
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```
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* Checks whether type is an [Scoped enumeration](https://en.cppreference.com/w/cpp/language/enum#Scoped_enumerations).
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* Provides the member constant value which is equal to true, if T is an [Scoped enumeration](https://en.cppreference.com/w/cpp/language/enum#Scoped_enumerations) type. Otherwise, value is equal to false.
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* Examples
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```cpp
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magic_enum::is_scoped_enum<color>::value -> false
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magic_enum::is_scoped_enum<Direction>::value -> true
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// Helper variable template.
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magic_enum::is_scoped_enum_v<Direction> -> true
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```
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## `underlying_type`
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```cpp
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template <typename T>
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struct underlying_type;
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template <typename T>
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using underlying_type_t = typename underlying_type<T>::type;
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```
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* Improved UB-free "SFINAE-friendly" [std::underlying_type](https://en.cppreference.com/w/cpp/types/underlying_type).
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* If T is a complete enumeration type, provides a member typedef type that names the underlying type of T. Otherwise, if T is not an enumeration type, there is no member type. Otherwise (T is an incomplete enumeration type), the program is ill-formed.
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* Examples
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```cpp
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magic_enum::underlying_type<color>::type -> int
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// Helper types.
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magic_enum::underlying_type_t<Direction> -> int
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```
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## `ostream_operators`
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```cpp
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template <typename Char, typename Traits, typename E>
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std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& os, E value);
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template <typename Char, typename Traits, typename E>
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std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& os, std::optional<E> value);
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```
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* Out-of-the-box ostream operators for enums.
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* Examples
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```cpp
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using namespace magic_enum::ostream_operators; // out-of-the-box ostream operators for enums.
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Color color = Color::BLUE;
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std::cout << color << std::endl; // "BLUE"
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```
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## `bitwise_operators`
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```cpp
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template <typename E>
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constexpr E operator~(E rhs) noexcept;
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template <typename E>
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constexpr E operator|(E lhs, E rhs) noexcept;
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template <typename E>
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constexpr E operator&(E lhs, E rhs) noexcept;
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template <typename E>
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constexpr E operator^(E lhs, E rhs) noexcept;
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template <typename E>
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constexpr E& operator|=(E& lhs, E rhs) noexcept;
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template <typename E>
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constexpr E& operator&=(E& lhs, E rhs) noexcept;
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template <typename E>
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constexpr E& operator^=(E& lhs, E rhs) noexcept;
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```
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* Out-of-the-box bitwise operators for enums.
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* Examples
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```cpp
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enum class Flags { A = 1 << 0, B = 1 << 1, C = 1 << 2, D = 1 << 3 };
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using namespace magic_enum::bitwise_operators; // out-of-the-box bitwise operators for enums.
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// Support operators: ~, |, &, ^, |=, &=, ^=.
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Flags flags = Flags::A | Flags::B & ~Flags::C;
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```
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