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

NAME
       std::is_integral	- std::is_integral

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

	  std::is_integral is a	UnaryTypeTrait.

	  Checks  whether  T is	an integral type. Provides the member constant
       value which is
	  equal	to true, if T is the type bool,	char
	  , char8_t
	  (since C++20), char16_t, char32_t, wchar_t, short, int,  long,  long
       long, or	any
	  implementation-defined extended integer types, including any signed,
       unsigned, and
	  cv-qualified variants. Otherwise, value is equal to false.

	  If   the   program  adds  specializations  for  std::is_integral  or
       std::is_integral_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_integral_v =	is_integral<T>::value;

       Inherited from std::integral_constant

Member constants
	  value	   true	if T is	an integral 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
	  // Note: this	implementation uses C++20 facilities
	  template<class T>
	  struct is_integral : std::bool_constant<
	      requires (T t, T*	p, void	(*f)(T)) // T* parameter excludes ref-
       erence types
	      {
		  reinterpret_cast<T>(t); // Exclude class types
		  f(0);	// Exclude enumeration types
		  p + t; // Exclude everything not yet excluded	 but  integral
       types
	      }> {};

Example
       // Run this code

	#include <type_traits>

	static_assert
	(
	    std::is_integral_v<float> == false &&
	    std::is_integral_v<int*> ==	false &&
	    std::is_integral_v<int> == true &&
	    std::is_integral_v<const int> == true &&
	    std::is_integral_v<bool> ==	true &&
	    std::is_integral_v<char> ==	true
	);

	class A	{};
	static_assert(std::is_integral_v<A> == false);

	struct B { int x:4; };
	static_assert(std::is_integral_v<B> == false);
	using BF = decltype(B::x); // bit-field's type
	static_assert(std::is_integral_v<BF> ==	true);

	enum E : int {};
	static_assert(std::is_integral_v<E> == false);

	template <class	T>
	constexpr T same(T i)
	{
	    static_assert(std::is_integral<T>::value, "Integral	required.");
	    return i;
	}
	static_assert(same('"')	== 042);

	int main() {}

See also
	  integral	    specifies that a type is an	integral type
	  (C++20)	    (concept)
	  is_integer	    identifies integer types
	  [static]	      (public	static	member	constant  of  std::nu-
       meric_limits<T>)
	  is_floating_point checks if a	type is	a floating-point type
	  (C++11)	    (class template)
	  is_arithmetic	    checks if a	type is	an arithmetic type
	  (C++11)	    (class template)
	  is_enum	    checks if a	type is	an enumeration type
	  (C++11)	    (class template)

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

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