SIGNBIT(3) Linux Programmer's Manual SIGNBIT(3)NAMEsignbit - test sign of a real floating-point number
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
signbit(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99
DESCRIPTIONsignbit() is a generic macro which can work on all real floating-point
types. It returns a non-zero value if the value of x has its sign bit
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 sign‐
bit(-0.0) will return a non-zero value.
NaNs and infinities have a sign bit.
The signbit() macro returns non-zero if the sign of x is negative; oth‐
erwise it returns zero.
No errors occur.
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appen‐
dix with recommended functions in IEEE 754/IEEE 854).
This page is part of release 3.22 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/.
GNU 2008-08-05 SIGNBIT(3)