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 z_sqrt(doublecomplex *r, doublecomplex *z)
   7 {
   8         double mag, zi = z->i, zr = z->r;
   9
  10         if( (mag = f__cabs(zr, zi)) == 0.)
  11                 r->r = r->i = 0.;
  12         else if(zr > 0)
  13                 {
  14                 r->r = sqrt(0.5 * (mag + zr) );
  15                 r->i = zi / r->r / 2;
  16                 }
  17         else
  18                 {
  19                 r->i = sqrt(0.5 * (mag - zr) );
  20                 if(zi < 0)
  21                         r->i = - r->i;
  22                 r->r = zi / r->i / 2;
  23                 }
  24         }