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


std::is_unsigned - std::is_unsigned


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

If T is an integral 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.

The behavior of a program that adds specializations for is_unsigned
or is_unsigned_v
(since C++17) 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 {};


// 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
(C++11) (class template)
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)