| Defined in header <type_traits> | ||
|---|---|---|
template< class T > struct is_unsigned; | (since C++11) |
If T is an unsigned arithmetic type, provides the member constant value equal true. For any other type, value is false.
Template parameters
| T | - | a type to check |
Helper variable template
template< class T > 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 signed arithmetic type (class template) |
| (C++11) | checks if a type is floating-point type (class template) |
| (C++11) | checks if a type is integral type (class template) |
| (C++11) | makes the given integral type signed (class template) |
| (C++11) | makes the given integral type unsigned (class template) |
| std::experimental::is_unsigned_v
(library fundamentals TS) | variable template alias of std::is_unsigned::value (variable template) |
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