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/*
* IterationRule.java
*
* comments here.
*
* @author Michiaki Tatsubori
* @version %VERSION% %DATE%
* @see java.lang.Object
*
* COPYRIGHT 1998 by Michiaki Tatsubori, ALL RIGHTS RESERVED.
*/
package io.devnulllabs.openjava.syntax;
import io.devnulllabs.openjava.ptree.ObjectList;
import io.devnulllabs.openjava.ptree.ParseTree;
/**
* The class <code>IterationRule</code> represents iterative syntax
* rule.
* <p>
* Suppose there's a syntax rule A. This class can represents
* the syntax ( A )* or ( A )+
*
* @author Michiaki Tatsubori
* @version 1.0
* @since $Id: IterationRule.java,v 1.2 2003/02/19 02:54:31 tatsubori Exp $
* @see java.lang.Object
*/
public class IterationRule extends AbstractSyntaxRule
{
private SyntaxRule elementRule;
private boolean allowsEmpty;
/**
* Allocates a new rule representing iterations of a given rule.
*
* @param elementRule a rule to iterate
* @param allowsEmpty a flag to allow 0 iteration if it is true.
*/
public IterationRule( SyntaxRule elementRule, boolean allowsEmpty ) {
this.elementRule = elementRule;
this.allowsEmpty = allowsEmpty;
}
/**
* Allocates a new rule representing iterations of a given rule
* not allowing 0 iteration.
*
* @param elementRule a rule to iterate
*/
public IterationRule( SyntaxRule elementRule ) {
this( elementRule, false );
}
/**
* Consumes token source.
*
* @param token_src token source.
* @return null if this fails to consume a syntax tree represented
* by this object. Otherwise it returns <code>ObjectList</code> object.
*/
public ParseTree consume( TokenSource token_src )
throws SyntaxException
{
ObjectList result = new ObjectList();
if (! allowsEmpty) {
result.add( elementRule.consume( token_src ) );
}
while (elementRule.lookahead( token_src )) {
ParseTree elem = elementRule.consume( token_src );
result.add( elem );
}
return result;
}
}
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