libf2c/libF77/c_sqrt.c

   1 #include "f2c.h"
   2
   3 #undef abs
   4 #include "math.h"
   5 extern double f__cabs (double, double);
   6
   7 void
   8 c_sqrt (complex * r, complex * z)
   9 {
  10   double mag, t;
  11   double zi = z->i, zr = z->r;
  12
  13   if ((mag = f__cabs (zr, zi)) == 0.)
  14     r->r = r->i = 0.;
  15   else if (zr > 0)
  16     {
  17       r->r = t = sqrt (0.5 * (mag + zr));
  18       t = zi / t;
  19       r->i = 0.5 * t;
  20     }
  21   else
  22     {
  23       t = sqrt (0.5 * (mag - zr));
  24       if (zi < 0)
  25         t = -t;
  26       r->i = t;
  27       t = zi / t;
  28       r->r = 0.5 * t;
  29     }
  30 }