NAME
signbit() — floating-point sign-determination macro
SYNOPSIS
#include <math.h>
int signbit(
floating-type
x);
DESCRIPTION
The
signbit()
macro determines whether the sign of its argument value is negative.
The macro can be used with either
double
or
float
arguments, including infinities, zeros, and NaNs.
The ISO/ANSI C committee has approved the
signbit()
macro for inclusion in the C9X draft standard.
To use the
signbit()
macro, compile either with the default
-Ae
option or with the
-Aa
and
-D_HPUX_SOURCE
options. Make sure your program includes
<math.h>.
Link in the math library by specifying
-lm
on the compiler or linker command line.
RETURN VALUE
The
signbit()
macro returns a nonzero value if and only if the sign of its argument
value is negative.
ERRORS
No errors are defined.
EXAMPLE
Take certain actions if
x
is negative zero:
#include <math.h>
/*...*/
double x;
/*...*/
if ( (x == 0.0) && signbit(x) ) {
/*...*/
}
