redhat man page for signbit

SIGNBIT(3)							libc math functions							SIGNBIT(3)

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)

GNU
								    2002-08-10								SIGNBIT(3)