std::is_unsigned (3) - Linux Manuals

std::is_unsigned: std::is_unsigned


std::is_unsigned - std::is_unsigned


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

If T is an arithmetic type, provides the member constant value equal 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.

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 arithmetic type , false otherwise
         (public static member constant)

Member functions

              converts the object to bool, returns value
operator bool (public member function)

operator() returns value
              (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 {};


// Run this code

  #include <iostream>
  #include <type_traits>

  class A {};
  enum B : unsigned {};
  enum class C : unsigned {};

  int main()
      std::cout << std::boolalpha;
      std::cout << std::is_unsigned<A>::value << '\n';
      std::cout << std::is_unsigned<float>::value << '\n';
      std::cout << std::is_unsigned<signed int>::value << '\n';
      std::cout << std::is_unsigned<unsigned int>::value << '\n';
      std::cout << std::is_unsigned<B>::value << '\n';
      std::cout << std::is_unsigned<C>::value << '\n';



See also

is_signed checks if a type is a signed arithmetic type
              (class template)

is_arithmetic checks if a type is an arithmetic type
              (class template)

make_signed makes the given integral type signed
              (class template)

make_unsigned makes the given integral type unsigned
              (class template)