signbit
Header: <math.h>
Determines if the given floating-point number arg is negative. The macro returns an integral value.
# Declarations
#define signbit( arg ) /* implementation defined */
(since C99)
# Parameters
arg: floating-point value
# Return value
Nonzero integral value if arg is negative, 0 otherwise.
# Notes
This macro detects the sign bit of zeroes, infinities, and NaNs. Along with copysign, this macro is one of the only two portable ways to examine the sign of a NaN.
# Example
#include <math.h>
#include <stdio.h>
int main(void)
{
printf("signbit(+0.0) = %d\n", signbit(+0.0));
printf("signbit(-0.0) = %d\n", signbit(-0.0));
}