| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | SEE ALSO | COLOPHON | The Linux Programming Interface |
SIGNBIT(3) Linux Programmer's Manual SIGNBIT(3)
signbit - test sign of a real floating-point number
#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
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.
The signbit() macro returns nonzero if the sign of x is negative; otherwise it
returns zero.
No errors occur.
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).
copysign(3)
This page is part of release 3.32 of the Linux man-pages project. A
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at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-20 SIGNBIT(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface