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Showing content from https://en.cppreference.com/w/cpp/language/../algorithm/../ranges/../types/is_null_pointer.html below:

std::is_null_pointer - cppreference.com

template< class T > struct is_null_pointer;

(since C++11)

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.

If the program adds specializations for std::is_null_pointer or std::is_null_pointer_v(since C++17), the behavior is undefined.

[edit] Template parameters [edit] Helper variable template

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

(since C++17) Inherited from std::integral_constant Member constants true if T is the type std::nullptr_t (possibly cv-qualified), false otherwise
(public static member constant) Member functions converts the object to bool, returns value
(public member function) returns value
(public member function) Member types [edit] Possible implementation [edit] Notes

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

In libc++, std::is_null_pointer is not available in C++11 mode.

[edit] 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()
{
}

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior LWG 2247 C++11 the type trait for detecting std::nullptr_t was missing added [edit] See also checks if a type is void
(class template) [edit] checks if a type is an array type
(class template) [edit] checks if a type is a pointer type
(class template) [edit] checks if a type is an enumeration type
(class template) [edit] checks if a type is a union type
(class template) [edit] checks if a type is a non-union class type
(class template) [edit] checks if a type is a function type
(class template) [edit] checks if a type is an object type
(class template) [edit]

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