<xstd/ints/type_traits/is_signed.hpp>

xstd::is_signed, xstd::is_signed_v

template<class T>
constexpr bool is_signed_v = see below;

template<class T>
using is_signed = bool_constant<is_signed_v<T>>;

Whether a type is signed, for the built-in types and for integer-class types alike.

Value

std::is_signed_v<T>, except for a possibly cv-qualified type that models integer_class and is not std::integral; there, static_cast<I>(-1) < static_cast<I>(0) for I the cv-unqualified type.

Remarks

is_signed is an alias, not a class template. An integer-class type reaches the trait by modelling integer_class, not by specializing it.

Notes

• It agrees with std::is_signed_v on int, unsigned, double and void.
• It is true for every signed exact-width type, the 128-bit, Boost, Abseil and bit-precise ones included, const or not, and false for every unsigned one.
• It is true for int128 under every cv-qualification, a class type on one toolchain.
• An incomplete class type gives false rather than an error.

See also

Entity	Relation
is_unsigned	the other half
signed_integer	the concept that reads it
integer_class	what a class type models to reach it
std::is_signed	the standard trait it extends