c_sqrt.c   [plain text]

#include "f2c.h"

#undef abs
#include "math.h"
extern double f__cabs (double, double);

void
c_sqrt (complex * r, complex * z)
{
  double mag, t;
  double zi = z->i, zr = z->r;

  if ((mag = f__cabs (zr, zi)) == 0.)
    r->r = r->i = 0.;
  else if (zr > 0)
    {
      r->r = t = sqrt (0.5 * (mag + zr));
      t = zi / t;
      r->i = 0.5 * t;
    }
  else
    {
      t = sqrt (0.5 * (mag - zr));
      if (zi < 0)
	t = -t;
      r->i = t;
      t = zi / t;
      r->r = 0.5 * t;
    }
}