std::is_fundamental

< cpp‎ | types

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

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 is_fundamental or is_fundamental_v (since C++17) is undefined.

Template parameters

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 <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

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)