1 extern int __fpclassifyd (double x);
2 
fdim(double x,double y)3 double fdim (double x, double y)
4 {
5    int c = __fpclassifyd (x);
6    if (c == 0)
7      return (x);
8    if (__fpclassifyd (y) == 0)
9      return (y);
10    if (c == 1)
11      return (__builtin_huge_val ());
12    return x > y ? x - y : 0.0;
13 }
14