libf2c/libF77/z_sqrt.c

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