package gve.calc.formula;

import java.util.*;

 Somt elementen van een door komma's gescheiden lijst op. 
public class CommaEnumerator implements Enumeration {
	private Part nextPart;

	public CommaEnumerator(Part p) {
		nextPart = p;
	}

	public boolean hasMoreElements() {
		if (nextPart == null) return false;
		if ((nextPart instanceof Identifier) && ((Identifier)nextPart).isEmpty()) {
			nextPart = null;
			return false;
		}
		return true;
	}

	public Part nextPart() {
		if (!hasMoreElements()) throw new NoSuchElementException();
		if (nextPart instanceof OperatorComma) {
			OperatorComma comma = (OperatorComma)nextPart;
			nextPart = comma.right;
			return comma.left;
		}
		Part result = nextPart;
		nextPart = null;
		return result;
	}

	public Object nextElement() { return nextPart(); }
}