isnan()

Arguments:

x

The number you want to test.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

The isnan() macro determines if x is Not-A-Number (NaN).

Returns:

Nonzero

The value of x is NaN.

0

The value of x is a number.

Examples:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char** argv) 
{
  double a, b, c, d;

  a = 2;
  b = -0.5;
  c = NAN;
  d = 1.0/0.0;
  printf("%f is %s \n", a, 
         (isnan(a)) ? "not a number" : "a number");
  printf("%f is %s \n", b,
         (isnan(b)) ? "not a number" : "a number");
  printf("%f is %s \n", c,
         (isnan(c)) ? "not a number" : "a number");
  printf("%f is %s \n", d,
         (isnan(d)) ? "not a number" : "a number");
  return EXIT_SUCCESS;
}

produces the output:

2.000000 is a number
-0.500000 is a number
nan is not a number
inf is a number

Classification:

POSIX 1003.1