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

NAME
     std::is_unsigned - std::is_unsigned

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

	std::is_unsigned is a UnaryTypeTrait.

	If  T is an arithmetic type, provides the member constant value equal to
     true if T(0)
	< T(-1): this results in true for the unsigned	integer  types	and  the
     type bool and
	in false for the signed integer types and the floating-point types.

	For any other type, value is false.

	If  the program adds specializations for std::is_unsigned or std::is_un-
     signed_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_unsigned_v = is_unsigned<T>::value;

     Inherited from std::integral_constant

Member constants
	value	 true if T is an unsigned 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
	namespace detail
	{
	    template<typename T,bool = std::is_arithmetic<T>::value>
	    struct is_unsigned : std::integral_constant<bool, T(0) < T(-1)> {};

	    template<typename T>
	    struct is_unsigned<T,false> : std::false_type {};
	} // namespace detail

	template<typename T>
	struct is_unsigned : detail::is_unsigned<T>::type {};

Example
     // Run this code

      #include <iostream>
      #include <type_traits>

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

      enum B : unsigned {};
      static_assert(std::is_unsigned_v<B> == false);

      enum class C : unsigned {};
      static_assert(std::is_unsigned_v<C> == false);

      struct S { unsigned p : 1; int q : 1; };
      static_assert(
	  std::is_unsigned_v<decltype(S::p)> not_eq
	  std::is_unsigned_v<decltype(S::q)>
      );

      static_assert(
	  std::is_unsigned_v<float> == false &&
	  std::is_unsigned_v<signed int> == false &&
	  std::is_unsigned_v<unsigned int> == true &&
	  std::is_unsigned_v<bool> == true
      );

      int main()
      {
	  std::cout << std::boolalpha << std::is_unsigned<char>::value << '\n';
      }

Possible output:
      false

See also
	is_signed     checks if a type is a signed arithmetic type
	(C++11)       (class template)
	is_signed     identifies signed types
	[static]      (public static member constant of std::numeric_limits<T>)
	is_arithmetic checks if a type is an arithmetic type
	(C++11)       (class template)
	make_signed   makes the given integral type signed
	(C++11)       (class template)
	make_unsigned makes the given integral type unsigned
	(C++11)       (class template)

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