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

NAME
     std::is_fundamental - std::is_fundamental

Synopsis
	Defined in header <type_traits>
	template< class T >		 (since C++11)
	struct is_fundamental;

	std::is_fundamental is a UnaryTypeTrait.

	If  T  is  a  fundamental  type  (that	is,  arithmetic  type,	void, or
     nullptr_t), 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
	T - a type to check

	Helper variable template

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

     Inherited from std::integral_constant

Member constants
	value	 true if T is a fundamental type, false otherwise
	[static] (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_fundamental
	    : std::integral_constant<
		bool,
		std::is_arithmetic<T>::value ||
		std::is_void<T>::value ||
		std::is_same<std::nullptr_t,	      typename		std::re-
     move_cv<T>::type>::value
		//  you can also use 'std::is_null_pointer<T>::value' instead in
     C++14
	> {};

Example
     // Run this code

      #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() {}

See also
	is_compound	checks if a type is a compound type
	(C++11) 	(class template)
	is_arithmetic	checks if a type is an arithmetic type
	(C++11) 	(class template)
	is_void 	checks if a type is void
	(C++11) 	(class template)
	is_null_pointer checks if a type is std::nullptr_t
	(C++14) 	(class template)

http://cppreference.com 	   2024.06.10		  std::is_fundamental(3)
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