Linux 2.6 - man page for signbit (linux section 3)
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SIGNBIT(3) Linux Programmer's Manual SIGNBIT(3)
signbit - test sign of a real floating-point number
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
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.
The signbit() macro returns nonzero if the sign of x is negative; otherwise it returns
No errors occur.
Multithreading (see pthreads(7))
The signbit() macro is thread-safe.
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 3.55 of the Linux man-pages project. A description of the
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GNU 2013-07-04 SIGNBIT(3)
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