home | help 
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;

	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.

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-qualified),
     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	   Value    Std 	Feature
	__cpp_lib_is_null_pointer 201309L (C++14) std::is_null_pointer

Example
     // Run this code

      #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
	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 a 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 	   2024.06.10		 std::is_null_pointer(3)
home | help