/*
 * @(#)$Id: ExpressionFinder.java,v 1.1 2002/02/24 01:29:04 kk122374 Exp $
 *
 * Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */
package com.sun.msv.grammar.util;

import com.sun.msv.grammar.*;

/**
 * Base class for "finding" something from an expression.
 * 
 * This class visits all reachable expressions and returns boolean.
 * 
 * In any binary expression, if one branch returns true, then the binary
 * expression itself returns true. Thus it can be used to find something
 * from an expression.
 * 
 * Note that unless the derived class do something, this implementation
 * will recurse infinitely.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public abstract class ExpressionFinder implements ExpressionVisitorBoolean
{
	public boolean onSequence( SequenceExp exp )		{ return exp.exp1.visit(this)||exp.exp2.visit(this); }
	public boolean onInterleave( InterleaveExp exp )	{ return exp.exp1.visit(this)||exp.exp2.visit(this); }
	public boolean onConcur( ConcurExp exp )			{ return exp.exp1.visit(this)||exp.exp2.visit(this); }
	public boolean onChoice( ChoiceExp exp )			{ return exp.exp1.visit(this)||exp.exp2.visit(this); }
	public boolean onAttribute( AttributeExp exp )		{ return exp.exp.visit(this); }
	public boolean onElement( ElementExp exp )			{ return exp.contentModel.visit(this); }
	public boolean onOneOrMore( OneOrMoreExp exp )		{ return exp.exp.visit(this); }
	public boolean onMixed( MixedExp exp )				{ return exp.exp.visit(this); }
	public boolean onList( ListExp exp )				{ return exp.exp.visit(this); }
	public boolean onRef( ReferenceExp exp )			{ return exp.exp.visit(this); }
	public boolean onOther( OtherExp exp )				{ return exp.exp.visit(this); }
	public boolean onEpsilon()							{ return false; }
	public boolean onNullSet()							{ return false; }
	public boolean onAnyString()						{ return false; }
	public boolean onData( DataExp exp )				{ return false; }
	public boolean onValue( ValueExp exp )				{ return false; }
}