signbit(3) -- Linux man page
NAME
signbit - test sign of a real floating point number
SYNOPSIS
#include <math.h>
int signbit (X);
DESCRIPTION
`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.
CONFORMING TO
This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).
SEE ALSO
copysign(3)
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