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)): signbit(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; 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.
CONFORMING TO
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
SEE ALSO
COLOPHON
- This page is part of release 3.25 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.