std::is_signed
From cppreference.com
Defined in header
<type_traits>
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||
template< class T >
struct is_signed; |
(since C++11) | |
If T
is a signed arithmetic type, provides the member constant value
equal true. For any other type, value
is false.
Contents |
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)
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returns value (public member function) |
Member types
Type | Definition |
value_type
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bool
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type
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std::integral_constant<bool, value> |
[edit] 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 {}; |
[edit] 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
[edit] See also
(C++11)
|
checks if a type is unsigned arithmetic type (class template) |
[static]
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identifies signed types (public static member constant of std::numeric_limits )
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(C++11)
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checks if a type is floating-point type (class template) |
(C++11)
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checks if a type is integral type (class template) |
(C++11)
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makes the given integral type signed (class template) |
(C++11)
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makes the given integral type unsigned (class template) |
(library fundamentals TS)
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variable template alias of std::is_signed::value (variable template) |