std::numeric_limits<T>:: is_signed

The value of std:: numeric_limits < T > :: is_signed is true for all signed arithmetic types T and false for the unsigned types. This constant is meaningful for all specializations.

Standard specializations

Example

#include <iostream>
#include <iomanip>
#include <limits>
 
template<typename T>
struct test
{
    test(const char* name, int w = 15)
    {
        std::cout
            << std::left << std::setw(w)
            << (std::numeric_limits<T>::is_specialized ? name : "non-specialized")
            << " : "
            << (std::numeric_limits<T>::is_signed ? "" : "un") << "signed\n";
    }
};
 
int main()
{
    test<bool>{"bool"};
    test<char>{"char"};
    test<wchar_t>{"wchar_t"};
    test<char16_t>{"char16_t"};
    test<char32_t>{"char32_t"};
    test<float>{"float"};
    struct delusion{};
    test<delusion>{"delusion"};
    test<decltype(42)>{"decltype(42)"};
}

bool            : unsigned
char            : signed
wchar_t         : signed
char16_t        : unsigned
char32_t        : unsigned
float           : signed
non-specialized : unsigned
decltype(42)    : signed

See also