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std::is_fundamental

Defined in header <type_traits> 
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.

The behavior of a program that adds specializations for std::is_fundamental or std::is_fundamental_v is undefined.

Template parameters

T - a type to check

Helper variable template

template< class T >
inline constexpr bool is_fundamental_v = is_fundamental<T>::value;
 (since C++17)

Inherited from std::integral_constant

Member constants

value
[static]
true if T is a fundamental 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>

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

(C++11)
checks if a type is a compound type
(class template)
(C++11)
checks if a type is an arithmetic type
(class template)
(C++11)
checks if a type is void
(class template)
(C++14)
checks if a type is std::nullptr_t
(class template)

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https://en.cppreference.com/w/cpp/types/is_fundamental