lib/other/hypot.c

   1 /*
   2  * (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
   3  * See the copyright notice in the ACK home directory, in the file "Copyright".
   4  *
   5  * Author: Ceriel J.H. Jacobs
   6  */
   7
   8 #include <math.h>
   9
  10 struct complex {
  11         double r,i;
  12 };
  13
  14 _PROTOTYPE(double hypot, (double x, double y ));
  15 _PROTOTYPE(double cabs, (struct complex p_compl ));
  16
  17 /* $Header$ */
  18
  19 double
  20 hypot(x, y)
  21 double x, y;
  22 {
  23         /*      Computes sqrt(x*x+y*y), avoiding overflow */
  24
  25         if (x < 0) x = -x;
  26         if (y < 0) y = -y;
  27         if (x > y) {
  28                 double t = y;
  29                 y = x;
  30                 x = t;
  31         }
  32         /* sqrt(x*x+y*y) = sqrt(y*y*(x*x/(y*y)+1.0)) = y*sqrt(x*x/(y*y)+1.0) */
  33         if (y == 0.0) return 0.0;
  34         x /= y;
  35         return y*sqrt(x*x+1.0);
  36 }
  37
  38 double
  39 cabs(p_compl)
  40 struct complex p_compl;
  41 {
  42         return hypot(p_compl.r, p_compl.i);
  43 }