std::is_unsigned

 

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

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 > 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 integral 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

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';
}

Output:

false
false
false
true
false
false

See also

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