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std::is_null_pointer(3)	      C++ Standard Libary      std::is_null_pointer(3)

NAME
       std::is_null_pointer - std::is_null_pointer

Synopsis
	  Defined in header <type_traits>
	  template< class T >		   (since C++14)
	  struct is_null_pointer;

	  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
       is_null_pointer
	  or is_null_pointer_v
	  (since C++17)	is undefined.

Template parameters
	  T - a	type to	check

	 Helper	variable template

	  template<		    class		  T		     >
       (since C++17)
	  inline constexpr bool	is_null_pointer_v = is_null_pointer<T>::value;

       Inherited from std::integral_constant

Member constants
	  value	    true  if  T	is the type std::nullptr_t (possibly cv-quali-
       fied) , false
	  [static] otherwise
		   (public static member constant)

Member functions
	  operator bool	converts the object to bool, returns value
			(public	member function)
	  operator()	returns	value
	  (C++14)	(public	member function)

Member types
	  Type	     Definition
	  value_type bool
	  type	     std::integral_constant<bool, value>

Possible implementation
	  template< class T >
	  struct  is_null_pointer  :   std::is_same<std::nullptr_t,   std::re-
       move_cv_t<T>> {};

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

	  Feature-test macro: __cpp_lib_is_null_pointer

Example
       // Run this code

	#include <iostream>
	#include <type_traits>

	int main()
	{
	    std::cout << std::boolalpha
		      << std::is_null_pointer< decltype(nullptr) >::value << '
       '
		      << std::is_null_pointer< int* >::value <<	'\n'
		      << std::is_pointer< decltype(nullptr) >::value <<	' '
		      << std::is_pointer<int*>::value << '\n';
	}

Output:
	true false
	false true

See also
	  is_void     checks if	a type is void
	  (C++11)     (class template)
	  is_array    checks if	a type is an array type
	  (C++11)     (class template)
	  is_pointer  checks if	a type is a pointer type
	  (C++11)     (class template)
	  is_enum     checks if	a type is an enumeration type
	  (C++11)     (class template)
	  is_union    checks if	a type is an union type
	  (C++11)     (class template)
	  is_class    checks if	a type is a non-union class type
	  (C++11)     (class template)
	  is_function checks if	a type is a function type
	  (C++11)     (class template)
	  is_object   checks if	a type is an object type
	  (C++11)     (class template)

http://cppreference.com		  2022.07.31	       std::is_null_pointer(3)

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