// Let's see if we can use this function in place of 
// the sqrt() function that is in the C math library.
//
// If we use this function, our main program should NOT
// include math.h, and our link command should NOT use "-lm".
//
double sqrt ( double s )
{
  double e;
  double r1;
  double r2;

  r1 = 1.0;

  while ( 1 )
  {
    r2 = s / r1;
    e = fabs ( s - r1 * r1 );
    if ( e < 0.000000001 )
    {
      break;
    }
    r1 = ( r1 + r2 ) / 2;
  }

  return r1;
}