[antlr-interest] (Newbie) tree walker emits "GrammarSanity.traceStatesLookingForLeftRecursion "

[ali azimi]

  Hi,
   
  Thank you so much for your advice. What do you think the NullPointer error message would be for? I checked my grammar again and again, however without any success. I produced another tree walker very similar to this one and also as large. It works perfectly. I recall that I had some NullPointer error messages for previous one. I sorted it out by putting some imaginary nodes as roots for some rules when needed. I am a newbie and started to learn whole of this subject nearly a month ago. I think an expert eye would pick the problem very quickly. Could you give me another advice so that I will not sit in front of my laptop and stare at the codes emotionlessly?
   
  Thank you all a million time. Without you I would not have been able to come even this far.
  Best regards,
   
  Al

Cameron Palmer <cameron.palmer at gmail.com> wrote:
   
  It sounds like your Main program isn't correctly handing off the
output of the Lexer-Parser to the Walker. I would verify that is
correct. I think the error message you are seeing is just a
consequence of the Null Pointer Exception.

Cameron Palmer
University of North Texas

On 8/9/07, ali azimi wrote:
> Hi,
>
> Thank you in advance for any advice.
>
> When I run my tree walker I receive some error messages which can be seen at
> the bottom of this page. The grammar is too long and can not be posted. I
> have tried to make sure that the grammar does not have any left recursion
> problem. The error messages do not give me adequate information as to where
> these errors are likely to be originated from. What would you suggest me to
> do?
>
> I appreciate any help a lot.
>
> Best regards,
>
> Al
>
> Errors:
>
> Check Grammar failed:
>
> (10): internal error: C:\Documents and
> Settings\ali\Desktop\antlr\FpCif12Walker.g:
> java.lang.NullPointerException
>
> Org.antlr.tool.GrammarSanity.traceStatesLookingForLeftRecursion
> (Unknown Source)
> Org.antlr.tool.GrammarSanity.checkAllRulesForLeftRecursion
> (Unknown Source)
>
> Org.antlr.tool.Grammar. checkAllRulesForLeftRecursion (Unknown Source)
>
> Org.antlr.codegen.CodeGenerator.genRecognizer (Unknown
> Source)
>
> Org.antlr.Tool.processGrammar (Unknown Source)
>
> Org.antlr.Tool. process (Unknown Source)
>
> Org.antlr.works.generate.CodeGenerate.generate
> (CodeGenerate.java:125)
>
> Org.antlr.works.generate.CodeGenerate.run
> (CodeGenerate.java:251)
>
> Java.lang.Thread.run (Unknown Source)
>
>
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