std::is_enum

Defined in header `<type_traits>`
template< class T > struct is_enum;		(since C++11)

std::is_enum is a UnaryTypeTrait.

Checks whether T is an enumeration type. Provides the member constant value which is equal to true, if T is an enumeration type. Otherwise, value is equal to false.

If the program adds specializations for std::is_enum or std::is_enum_v, the behavior is undefined.

Template parameters

a type to check

Helper variable template

template< class T >
constexpr bool is_enum_v = is_enum<T>::value;

(since C++17)

Inherited from std::integral_constant

Member constants

value

[static]

true if T is an enumeration type, false otherwise
(public static member constant)

Member functions

operator bool	converts the object to bool, returns `value` (public member function)
operator() (C++14)	returns `value` (public member function)

Member types

Type	Definition
`value_type`	bool
`type`	std::integral_constant<bool,value>

Example

#include <type_traits>

struct A { enum E { e }; };
static_assert(!std::is_enum_v<A>);
static_assert(std::is_enum_v<A::E>);
static_assert(std::is_enum_v<decltype(A::E::e)>);

enum E {};
static_assert(std::is_enum_v<E>);
static_assert(std::is_enum_v<const E>, "Constness is ignored");
static_assert(!std::is_enum_v<E&>, "References matter");

enum class E1 : int { e };
static_assert(std::is_enum_v<E1>);
static_assert(std::is_enum_v<decltype(E1::e)>);

static_assert(!std::is_enum_v<int>);

enum class E2;
static_assert(std::is_enum_v<E2>, "Forward-declared scoped enum");

enum class E3 : char;
static_assert(std::is_enum_v<E3>, "Forward-declared scoped enum with explicit base type");

int main() {}

is_integral (C++11)	checks if a type is an integral type (class template)
is_arithmetic (C++11)	checks if a type is an arithmetic type (class template)
is_scalar (C++11)	checks if a type is a scalar type (class template)
is_scoped_enum (C++23)	checks if a type is a scoped enumeration type (class template)
is_enumerator (C++26)	checks if reflection represents an enumerator (function)
is_enum_type (C++26)	checks if reflected type is an enumeration type (function)

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https://en.cppreference.com/cpp/types/is_enum