libf2c/libF77/z_sqrt.c

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