 signbit(3)  phpMan
SIGNBIT(3) Linux Programmer's Manual SIGNBIT(3)
NAME
signbit  test sign of a real floatingpoint number
SYNOPSIS
#include <math.h>
int signbit(x);
Link with lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
signbit():
_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 floatingpoint 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.
ATTRIBUTES
Multithreading (see pthreads(7))
The signbit() macro is threadsafe.
CONFORMING TO
C99, POSIX.12001. This function is defined in IEC 559 (and the appendix with recommended
functions in IEEE 754/IEEE 854).
SEE ALSO
copysign(3)
COLOPHON
This page is part of release 3.74 of the Linux manpages 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/manpages/.
GNU 20130704 SIGNBIT(3)
