тестовый знак реального числа с плавающей запятой (test sign of a real floating-point number)
Имя (Name)
signbit - test sign of a real floating-point number
Синопсис (Synopsis)
#include <math.h>
int signbit(x);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
signbit():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
Описание (Description)
signbit() is a generic macro which can work on all real floating-
point types. It returns a nonzero value if the value of x has
its sign bit set.
This is not the same as x < 0.0, because IEEE 754 floating point
allows zero to be signed. The comparison -0.0 < 0.0 is false,
but signbit(-0.0) will return a nonzero value.
NaNs and infinities have a sign bit.
Возвращаемое значение (Return value)
The signbit() macro returns nonzero if the sign of x is negative;
otherwise it returns zero.
Ошибки (Error)
No errors occur.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│signbit() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008, C99. This function is defined in IEC
559 (and the appendix with recommended functions in IEEE 754/IEEE
854).
Смотри также (See also)
copysign(3)
