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std::is_fundamental - cppreference.com

From cppreference.com

template< class T > struct is_fundamental;

 (since C++11)

std::is_fundamental is a UnaryTypeTrait.

If T is a fundamental type (that is, arithmetic type, void, or nullptr_t), provides the member constant value equal true. For any other type, value is false.

If the program adds specializations for std::is_fundamental or std::is_fundamental_v, the behavior is undefined.

Template parameters

Helper variable template

template< class T > constexpr bool is_fundamental_v = is_fundamental<T>::value;

 (since C++17)

Inherited from std::integral_constant

Member constants

true if T is a fundamental 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

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

Possible implementation

template<class T>
struct is_fundamental
    : std::integral_constant<
        bool,
        std::is_arithmetic<T>::value ||
        std::is_void<T>::value ||
        std::is_same<std::nullptr_t, typename std::remove_cv<T>::type>::value
        // you can also use 'std::is_null_pointer<T>::value' instead in C++14
> {};

Example

#include <type_traits>

static_assert(std::is_fundamental_v<int> == true);
static_assert(std::is_fundamental_v<int&> == false);
static_assert(std::is_fundamental_v<int*> == false);
static_assert(std::is_fundamental_v<void> == true);
static_assert(std::is_fundamental_v<void*> == false);
static_assert(std::is_fundamental_v<float> == true);
static_assert(std::is_fundamental_v<float&> == false);
static_assert(std::is_fundamental_v<float*> == false);
static_assert(std::is_fundamental_v<std::nullptr_t> == true);
static_assert(std::is_fundamental_v<std::is_fundamental<int>> == false);

class A {};
static_assert(std::is_fundamental_v<A> == false);
static_assert(std::is_fundamental_v<std::is_fundamental<A>::value_type>);

int main() {}

See also