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/*
* SeparatedListRule.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.ParseTree;
/**
* The class <code>SeparatedListRule</code> represents the syntax
* rule of a list separated by an separator.
* <p>
* Suppose there's a syntax rule A and token t. This class can
* represents the syntax A ( t A )*.
* <p>
*
* @author Michiaki Tatsubori
* @version 1.0
* @since $Id: SeparatedListRule.java,v 1.2 2003/02/19 02:54:32 tatsubori Exp $
* @see java.lang.Object
*/
public abstract class SeparatedListRule extends AbstractSyntaxRule {
private SyntaxRule elementRule;
private int separator;
private boolean allowsEmpty;
protected abstract void initList();
protected abstract void addListElement(Object elem);
protected abstract ParseTree getList();
/**
* Allocates a new rule representing a list of a give rule
* separeted by a given separator.
*
* @param elementRule a rule of each element of the list
* @param separator_token the id of a token to be separator
* @param allowEmpty a flag to allow 0 iteration if it is true.
* @see io.devnulllabs.openjava.syntax.TokenID
*/
public SeparatedListRule(
SyntaxRule elementRule,
int separator_token,
boolean allowsEmpty) {
this.elementRule = elementRule;
this.separator = separator_token;
this.allowsEmpty = allowsEmpty;
}
/**
* Allocates a new rule representing a list of a give rule
* separeted by a given separator.
*
* @param elementRule a rule of each element of the list
* @param separator_token the id of a token to be separator
* @see io.devnulllabs.openjava.syntax.TokenID
*/
public SeparatedListRule(SyntaxRule elementRule, int separator_token) {
this(elementRule, separator_token, 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 final ParseTree consume(TokenSource token_src)
throws SyntaxException {
initList();
ParseTree elem;
if (!allowsEmpty) {
elem = elementRule.consume(token_src);
addListElement(elem);
}
CompositeRule spy =
new CompositeRule(new TokenRule(separator), elementRule);
while (spy.lookahead(token_src)) {
elem = consumeSepAndElem(token_src);
addListElement(elem);
}
return getList();
}
private ParseTree consumeSepAndElem(TokenSource token_src)
throws SyntaxException {
token_src.getNextToken(); /* separator */
return elementRule.consume(token_src);
}
}
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