# 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 an 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` (since C++17) 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

Run this code

    #include <iostream>
    #include <type_traits>

    class A {};

    int main()
    {
        std::cout << std::boolalpha;
        std::cout << "A\t"      << std::is_fundamental<A>::value << '\n';
        std::cout << "int\t"    << std::is_fundamental<int>::value << '\n';
        std::cout << "int&\t"   << std::is_fundamental<int&>::value << '\n';
        std::cout << "int*\t"   << std::is_fundamental<int*>::value << '\n';
        std::cout << "float\t"  << std::is_fundamental<float>::value << '\n';
        std::cout << "float&\t" << std::is_fundamental<float&>::value << '\n';
        std::cout << "float*\t" << std::is_fundamental<float*>::value << '\n';
    }

Output:

    A	false
    int	true
    int&	false
    int*	false
    float	true
    float&	false
    float*	false

### 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++14) | checks if a type is std::nullptr_t (class template)

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