Tests/Tutorial/Step4/MathFunctions/mysqrt.cxx


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#include <stdio.h>
#include "MathFunctions.h"
#include "TutorialConfig.h"

#include <math.h>

// a hack square root calculation using simple operations
double mysqrt(double x)
{
  if (x <= 0)
    {
    return 0;
    }

  double result;

  // if we have both log and exp then use them
#if defined(HAVE_LOG) && defined (HAVE_EXP)
  result = exp(log(x)*0.5);
  fprintf(stdout,"Computing sqrt of %g to be %g using log\n",x,result);
#else
  double delta;
  result = x;

  // do ten iterations
  int i;
  for (i = 0; i < 10; ++i)
    {
    if (result <= 0)
      {
      result = 0.1;
      }
    delta = x - (result*result);
    result = result + 0.5*delta/result;
    fprintf(stdout,"Computing sqrt of %g to be %g\n",x,result);
    }
#endif
  return result;
}