# std::is_fundamental

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< cpp‎ | types

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.

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

### Template parameters

T | - | a type to check

### 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

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

Run this code

    #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

is_compound (C++11) | checks if a type is a compound type (class template)
is_arithmetic (C++11) | checks if a type is an arithmetic type (class template)
is_void (C++11) | checks if a type is void (class template)
is_null_pointer (C++11)(DR*) | checks if a type is std::nullptr_t (class template)

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