table of contents
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)):
signbit():
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.
ATTRIBUTES¶
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).
SEE ALSO¶
COLOPHON¶
This page is part of release 3.53 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/.
2013-07-04 | GNU |