std::is_signed
From cppreference.com
| Defined in header <type_traits>
|
||
| template< class T > struct is_signed; |
(since C++11) | |
If T is an arithmetic type, provides the member constant value equal true if T(-1) < T(0): this results in true for the floating-point types and the signed integer types, and in false for the unsigned integer types and the type bool.
For any other type, value is false.
Template parameters
| T | - | a type to check |
Helper variable template
| template< class T > inline constexpr bool is_signed_v = is_signed<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] |
true if T is a signed 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_signed : std::integral_constant<bool, T(-1) < T(0)> {}; template<typename T> struct is_signed<T,false> : std::false_type {}; } // namespace detail template<typename T> struct is_signed : detail::is_signed<T>::type {}; |
Example
Run this code
#include <iostream> #include <type_traits> class A {}; enum B : int {}; enum class C : int {}; int main() { std::cout << std::boolalpha; std::cout << std::is_signed<A>::value << '\n'; std::cout << std::is_signed<float>::value << '\n'; std::cout << std::is_signed<signed int>::value << '\n'; std::cout << std::is_signed<unsigned int>::value << '\n'; std::cout << std::is_signed<B>::value << '\n'; std::cout << std::is_signed<C>::value << '\n'; // shorter: std::cout << std::is_signed<signed int>() << '\n'; std::cout << std::is_signed<unsigned int>() << '\n'; }
Output:
false true true false false false true false
See also
| (C++11) |
checks if a type is unsigned arithmetic type (class template) |
| [static] |
identifies signed types (public static member constant of std::numeric_limits) |
| (C++11) |
checks if a type is arithmetic type (class template) |
| (C++11) |
makes the given integral type signed (class template) |
| (C++11) |
makes the given integral type unsigned (class template) |