package rpn.basic;

import java.util.Hashtable;
import rpn.Calculator;

public class ExchItem extends Item {
	
	public ExchItem(Calculator ca) {
		super(ca);
		ca.systemInstall(this);
	}
	
	public void exec() {
		if (ca.check(2)) {
			Item a = ca.pop();
			Item b = ca.pop();
			ca.push(a);
			ca.push(b);
		}
		else {
			ca.error(this, CalcErr.Underflow);
		}
	}
	
	public String toString() {
		return("exch");
	}
}