GNU/Linux man pages
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Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
Debian 6.0.4(Squeeze) |
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signbit(3) |
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signbit − test sign of a real floating-point number
#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
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 zero.
No errors occur.
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
copysign(3)
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signbit(3) | |