std::numeric_limits<T>::is_signed

 

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std::numeric_limits

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numeric_limits::is_specialized

numeric_limits::is_signed

numeric_limits::is_integer

numeric_limits::is_exact

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numeric_limits::quiet_NaN

numeric_limits::signaling_NaN

numeric_limits::denorm_min

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float_round_style

float_denorm_style

 

static const bool is_signed;		(until C++11)
static constexpr bool is_signed;		(since C++11)

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

T	value of std::numeric_limits<T>::is_signed
/* non-specialized */	false
bool	false
char	implementation-defined
signed char	true
unsigned char	false
wchar_t	implementation-defined
char8_t (since C++20)	false
char16_t (since C++11)	false
char32_t (since C++11)	false
short	true
unsigned short	false
int	true
unsigned int	false
long	true
unsigned long	false
long long (since C++11)	true
unsigned long long (since C++11)	false
float	true
double	true
long double	true

Example

Run this code

#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)"};
}

Possible output:

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

See also

is_signed (C++11)	checks if a type is a signed arithmetic type (class template)
is_integer [static]	identifies integer types (public static member constant)
is_exact [static]	identifies exact types (public static member constant)
is_bounded [static]	identifies types that represent a finite set of values (public static member constant)