/*
* @(#)$Id: ExpressionCloner.java,v 1.12 2001/10/18 23:52:09 Bear 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;
/**
* clones an expression.
*
* <p>
* By visiting an expression, returns a cloned expression.
*
* <p>
* This class is useless by itself since expressions are shared and unified.
* It should be used as a base class for various AGM-related tasks to modify
* AGM.
*
* <p>
* Note that this class doesn't provide default implementations for
* onAttribute, onElement, and onRef methods.
* Typically, the derived class needs to do something to prevent infinite recursion.
*
* @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
*/
public abstract class ExpressionCloner implements ExpressionVisitorExpression {
protected final ExpressionPool pool;
protected ExpressionCloner( ExpressionPool pool ) { this.pool = pool; }
public Expression onChoice( ChoiceExp exp ) {
Expression np1 = exp.exp1.visit(this);
Expression np2 = exp.exp2.visit(this);
if(exp.exp1==np1 && exp.exp2==np2) return exp;
else return pool.createChoice(np1,np2);
}
public Expression onOneOrMore( OneOrMoreExp exp ) {
Expression np = exp.exp.visit(this);
if(exp.exp==np) return exp;
else return pool.createOneOrMore(np);
}
public Expression onMixed( MixedExp exp ) {
Expression body = exp.exp.visit(this);
if(exp.exp==body) return exp;
else return pool.createMixed( body );
}
public Expression onList( ListExp exp ) {
Expression body = exp.exp.visit(this);
if(exp.exp==body) return exp;
else return pool.createList( body );
}
public Expression onSequence( SequenceExp exp ) {
Expression np1 = exp.exp1.visit(this);
Expression np2 = exp.exp2.visit(this);
if(exp.exp1==np1 && exp.exp2==np2) return exp;
else return pool.createSequence(np1,np2);
}
public Expression onConcur( ConcurExp exp ) {
return pool.createConcur(
exp.exp1.visit(this), exp.exp2.visit(this));
}
public Expression onInterleave( InterleaveExp exp ) {
return pool.createInterleave(
exp.exp1.visit(this), exp.exp2.visit(this));
}
public Expression onEpsilon() { return Expression.epsilon; }
public Expression onNullSet() { return Expression.nullSet; }
public Expression onAnyString() { return Expression.anyString; }
public Expression onData( DataExp exp ) { return exp; }
public Expression onValue( ValueExp exp ) { return exp; }
}