code: public boolean isShift(double tol) {
  		Point2D pt = transformWithoutShift(Point2D.construct(0.0, 1.0));
  		pt.y -= 1.0;
  		if (pt.sqrLength() > tol * tol)
  			return false;
  
  		pt = transformWithoutShift(Point2D.construct(1.0, 0.0));
  		pt.x -= 1.0;
  		return pt.sqrLength() <= tol * tol;
  	}
docs: Returns TRUE if this transformation is a shift transformation within the
  given tolerance.
  
  @param tol
  The tolerance value.