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, std::nullptr_t, std::meta::info(since C++26)), 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

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
#if __cpp_impl_reflection > 0
        || std::is_reflection_v<T>
#endif
> {};

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() {}

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)
is_reflection (C++26)	checks if a type is `std::meta::info` (class template)
is_fundamental_type (C++26)	checks if reflection represents a fundamental type (function)

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