import EDU.neu.ccs.demeter.dj.Visitor;
import java.util.Stack;

public class DifferenceVisitor extends Visitor
{
	Stack initials;
	SummingVisitor sv;
	
	DifferenceVisitor(SummingVisitor v){sv=v;}

	int getDifference(){ return sv.getTotal()-((Integer)initials.peek()).intValue();}

	public void start() {initials=new Stack();}
	
	public void before(Container host)
	{
		initials.push(new Integer(sv.getTotal()));
	}

	public void after(Container host)
	{
		initials.pop();
	}
}