NAME

std::numeric_limits::is_signed - std::numeric_limits::is_signed

Synopsis

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 (C++20) false
char16_t (C++11) false
char32_t (C++11) false
short true
unsigned short false
int true
unsigned int false
long true
unsigned long false
long long (C++11) true
unsigned long long (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 checks if a type is a signed arithmetic type
(C++11) (class template)
is_integer identifies integer types
[static] (public static member constant)
is_exact identifies exact types
[static] (public static member constant)
is_bounded identifies types that represent a finite set of values
[static] (public static member constant)