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SIGNBIT(3) | Linux Programmer's Manual | SIGNBIT(3) |
NAME¶
signbit - test sign of a real floating-point numberSYNOPSIS¶
#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 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¶
copysign(3)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/.2013-07-04 | GNU |