std::is_null_pointer

template< class T >
struct is_null_pointer;

std::is_null_pointer is a UnaryTypeTrait.

Checks whether T is the type std::nullptr_t.

Provides the member constant value that is equal to true, if T is the type std::nullptr_t, const std::nullptr_t, volatile std::nullptr_t, or const volatile std::nullptr_t.

Otherwise, value is equal to false.

The behavior of a program that adds specializations for std::is_null_pointer or std::is_null_pointer_v(since C++17) is undefined.

Template parameters

Helper variable template

template< class T >
inline constexpr bool is_null_pointer_v = is_null_pointer<T>::value;

Possible implementation

template<class T>
struct is_null_pointer : std::is_same<std::nullptr_t, std::remove_cv_t<T>> {};

Notes

std::is_pointer is false for std::nullptr_t because it is not a built-in pointer type.

Example

#include <type_traits>
 
static_assert(std::is_null_pointer_v<decltype(nullptr)>);
static_assert(!std::is_null_pointer_v<int*>);
static_assert(!std::is_pointer_v<decltype(nullptr)>);
static_assert(std::is_pointer_v<int*>);
 
int main()
{
}

See also