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POJavaCC Problem - Generated code doesn't find all parse errors
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  1. POJavaCC Problem - Generated code doesn't find all parse errors
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    copied!<p>Just started with JavaCC. But I have a strange behaviour with it. I want to verify input int the form of tokens (letters and numbers) wich are concatenated with signs (+, -, /) and wich can contain parenthesis. I hope that was understandable :)</p> <p>In the main method is a string, which should produce an error, because it has one opening but two closing parenthesis, but I do not get a parse exception --> Why?</p> <p>Does anybody have a clue why I don't get the exception?</p> <p>I was struggling with left recursion and choice conflicts with my initial try, but managed to get over them. Maybe there I introduced the problem?!</p> <p>Oh - and maybe my solution is not very good - ignore this fact... or better, give some advice ;-) </p> <p>File: CodeParser.jj</p> <pre><code> options { STATIC=false; } PARSER_BEGIN(CodeParser) package com.testing; import java.io.StringReader; import java.io.Reader; public class CodeParser { public CodeParser(String s) { this((Reader)(new StringReader(s))); } public static void main(String args[]) { try { /** String has one open, but two closing parenthesis --&gt; should produce parse error */ String s = "A+BC+-(2XXL+A/-B))"; CodeParser parser = new CodeParser(s); parser.expression(); } catch(Exception e) { e.printStackTrace(); } } } PARSER_END(CodeParser) TOKEN: { &lt;code : ("-")?(["A"-"Z", "0"-"9"])+ &gt; | &lt;op : ("+"|"/") &gt; | &lt;not : ("-") &gt; | &lt;lparenthesis : ("(") &gt; | &lt;rparenthesis : (")") &gt; } void expression() : { } { negated_expression() | parenthesis_expression() | LOOKAHEAD(2) operator_expression() | &lt;code&gt; } void negated_expression() : { } { &lt;not&gt;parenthesis_expression() } void parenthesis_expression() : { } { &lt;lparenthesis&gt;expression()&lt;rparenthesis&gt; } void operator_expression() : { } { &lt;code&gt;&lt;op&gt;expression() } </code></pre> <p><b>Edit - 11/16/2009</b></p> <p>Now I gave ANTLR a try.</p> <p>I changed some terms to better match my problem domain. I came up with the following code (using the answers on this site), which seems to do the work now:</p> <pre><code>grammar Code; CODE : ('A'..'Z'|'0'..'9')+; OP : '+'|'/'; start : terms EOF; terms : term (OP term)*; term : '-'? CODE | '-'? '(' terms ')'; </code></pre> <p>And by the way... ANTLRWORKS is a great tool for debugging/visualizing! Helped me a lot.</p> <p>Additional info<br/> Above code matches stuff like:</p> <pre><code>(-Z19+-Z07+((FV+((M005+(M272/M276))/((M278/M273/M642)+-M005)))/(FW+(M005+(M273/M278/M642)))))+(-Z19+-Z07+((FV+((M005+(M272/M276))/((M278/M273/M642/M651)+-M005)))/(FW+(M0)))) </code></pre>
 

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