SIGNBIT(3)

NAME
1.51 `signbit'-Does floating-point number have negative sign?

SYNOPSIS
     #include <math.h>
     int signbit(real-floating X);

DESCRIPTION
The `signbit' macro determines whether the sign of its argument value is negative. The macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is unsigned, it is treated as positive. As shown in the synopsis, the argument is "real-floating," meaning that any of the real floating-point types (float, double, etc.) may be given to it.
   Note that because of the possibilities of signed 0 and NaNs, the expression "X < 0.0" does not give the same result as `signbit' in all cases.

RETURNS
The `signbit' macro returns a nonzero value if and only if the sign of its argument value is negative.

PORTABILITY
C99, POSIX.

SEE ALSO
signbit is part of the library. The full documentation for is maintained as a Texinfo manual. If info and are properly installed at your site, the command

    info

will give you access to the complete manual.