c 判断数字是否无限

/* isinf example */
#include <stdio.h>      /* printf */
#include <math.h>       /* isinf, sqrt */

int main()
{
  printf ("isinf(0.0)       : %d\n",isinf(0.0));
  printf ("isinf(1.0/0.0)   : %d\n",isinf(1.0/0.0));
  printf ("isinf(-1.0/0.0)  : %d\n",isinf(-1.0/0.0));
  printf ("isinf(sqrt(-1.0)): %d\n",isinf(sqrt(-1.0)));
  return 0;
}

isfinite(0.0)       : 1
isfinite(1.0/0.0)   : 0
isfinite(-1.0/0.0)  : 0
isfinite(sqrt(-1.0)): 0