std::is_unsigned

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

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 >
inline constexpr bool is_unsigned_v = is_unsigned<T>::value;
(since C++17)

Inherited from std::integral_constant

Member constants

value
[static]
true if T is an unsigned arithmetic type , false otherwise
(public static member constant)

Member functions

operator bool
converts the object to bool, returns value
(public member function)
operator()
(C++14)
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 {};

Example

#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';
}

Output:

false
false
false
true
false
false

See also

(C++11)
checks if a type is a signed arithmetic type
(class template)
(C++11)
checks if a type is an arithmetic type
(class template)
(C++11)
makes the given integral type signed
(class template)
(C++11)
makes the given integral type unsigned
(class template)

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