libf2c/libF77/z_sqrt.c

   1 #include "f2c.h"
   2
   3 #ifdef KR_headers
   4 double sqrt(), f__cabs();
   5 VOID z_sqrt(resx, z) doublecomplex *resx, *z;
   6 #else
   7 #undef abs
   8 #include <math.h>
   9 extern double f__cabs(double, double);
  10 void z_sqrt(doublecomplex *resx, doublecomplex *z)
  11 #endif
  12 {
  13 double mag;
  14 doublecomplex res;
  15
  16 if( (mag = f__cabs(z->r, z->i)) == 0.)
  17         res.r = res.i = 0.;
  18 else if(z->r > 0)
  19         {
  20         res.r = sqrt(0.5 * (mag + z->r) );
  21         res.i = z->i / res.r / 2;
  22         }
  23 else
  24         {
  25         res.i = sqrt(0.5 * (mag - z->r) );
  26         if(z->i < 0)
  27                 res.i = - res.i;
  28         res.r = z->i / res.i / 2;
  29         }
  30
  31 resx->r = res.r;
  32 resx->i = res.i;
  33 }