# std::is_unsigned

From cppreference.com
< cpp‎ | types

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

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)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/types/is_unsigned&oldid=93143"