signbit — test sign of a real floating-point number
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
return a nonzero value.
NaNs and infinities have a sign bit.
signbit() macro returns
nonzero if the sign of
x is negative; otherwise it
For an explanation of the terms used in this section, see attributes(7).
POSIX.1-2001, POSIX.1-2008, C99. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
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Copyright 2002 Walter Harms (walter.harmsinformatik.uni-oldenburg.de)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
Distributed under GPL
Based on glibc infopages, copyright Free Software Foundation