Copyright (C) 2001, Geert Vernaeve. All Rights Reserved. 
package gve.calc.logic;

import java.util.Hashtable;
import java.util.Enumeration;
import gve.calc.formula.*;

 A FallbackMatcher uses another Matcher (the fallback) if it cannot find the type or value
  of a given symbol. It never modifies the contents of the fallback. 
public class FallbackMatcher extends Matcher {
	private Matcher fallback;

	public FallbackMatcher(Matcher fallback) {
		this.fallback = fallback;
	}
	
	public Object clone() {
		throw new Error("sorry, no clone (yet).");
	}

	public Part getPatternType(String symbol) {
		Part result = super.getPatternType(symbol);
		if (result == null) result = fallback.getPatternType(symbol);
		return result;
	}
	public Part getPatternType(Identifier symbol) { return getPatternType(symbol.getString()); }
	public Part getTomatchType(String symbol) {
		Part result = super.getTomatchType(symbol);
		if (result == null) result = fallback.getTomatchType(symbol);
		return result;
	}

	public Part getMatchedValue(String symbol) {
		Part result = super.getMatchedValue(symbol);
		if (result == null) result = fallback.getMatchedValue(symbol);
		return result;
	}

	public Enumeration tomatchSymbols() {
		return new FallbackEnumeration(super.tomatchSymbols(),fallback.tomatchSymbols());
	}

	public Enumeration matchedSymbols() {
		return new FallbackEnumeration(super.matchedSymbols(),fallback.matchedSymbols());
	}

	public void dump() {
		fallback.dump();
		super.dump();
	}

	protected boolean isFunction(String fname) {
		if(super.isFunction(fname)) return true;
		return fallback.isFunction(fname);
	}
}