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.
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 |
#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
|
(C++11) | checks if a type is a signed arithmetic type (class template) |
|
[static] | identifies integer types (public static member constant) |
|
[static] | identifies exact types (public static member constant) |
|
[static] | identifies types that represent a finite set of values (public static member constant) |
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https://en.cppreference.com/w/cpp/types/numeric_limits/is_signed