std::is_scoped_enum - cppreference.com (original) (raw)
| | | | | --------------------------------------------- | | ------------- | | template< class T > struct is_scoped_enum; | | (since C++23) |
std::is_scoped_enum is a UnaryTypeTrait.
Checks whether T is a scoped enumeration type. Provides the member constant value which is equal to true, if T is a scoped enumeration type. Otherwise, value is equal to false.
If the program adds specializations for std::is_scoped_enum or std::is_scoped_enum_v, the behavior is undefined.
Contents
[edit] Template parameters
[edit] Helper variable template
| template< class T > constexpr bool is_scoped_enum_v = is_scoped_enum<T>::value; | | (since C++23) | | --------------------------------------------------------------------------------------- | | ------------- |
Inherited from std::integral_constant
Member constants
| | true if T is a scoped enumeration type, false otherwise (public static member constant) | | ------------------------------------------------------------------------------------------ |
Member functions
| | converts the object to bool, returns value (public member function) | | ---------------------------------------------------------------------- | | | returns value (public member function) |
Member types
[edit] Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
| __cpp_lib_is_scoped_enum | 202011L | (C++23) | std::is_scoped_enum |
[edit] Possible implementation
namespace detail { void test_conversion(...); // selected when E is complete and scoped void test_conversion(int) = delete; // selected when E is complete and unscoped template concept is_scoped_enum_impl = std::is_enum_v && // checked first requires { detail::test_conversion(E{}); }; // ill-formed before overload resolution // when E is incomplete } // namespace detail template struct is_scoped_enum : std::bool_constant<detail::is_scoped_enum_impl> {};
[edit] Example
#include static_assert(std::is_scoped_enum_v == false); class A {}; static_assert(std::is_scoped_enum_v == false); enum B { self_test = std::is_scoped_enum_v }; static_assert(std::is_scoped_enum_v == false); static_assert(!self_test); enum struct C { final, import, module }; static_assert(std::is_scoped_enum_v == true); enum class D : int { pre, post, override }; static_assert(std::is_scoped_enum_v == true); enum class E; static_assert(std::is_scoped_enum_v == true); int main() {}