|SIGNBIT(3)||Linux Programmer's Manual||SIGNBIT(3)|
NAME¶signbit - test sign of a real floating-point number
SYNOPSIS¶#include <math.h> int signbit(x); Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;or cc -std=c99
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.
RETURN VALUE¶The signbit() macro returns nonzero if the sign of x is negative; otherwise it returns zero.
ERRORS¶No errors occur.
Multithreading (see pthreads(7))¶The signbit() macro is thread-safe.
CONFORMING TO¶C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
COLOPHON¶This page is part of release 3.74 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.