signbit — test sign of a real floating-point number
#include <math.h>
int
signbit( |
x); |
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signbit() 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 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 non-zero value.
NaNs and infinities have a sign bit.
The signbit() macro returns
non-zero if the sign of x is negative; otherwise it
returns zero.
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
This page is part of release 3.18 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/.
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Copyright 2002 Walter Harms (walter.harmsinformatik.uni-oldenburg.de) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpagesgmail.com> Distributed under GPL Based on glibc infopages |