[antlr-interest] Problems with the ANTLRworks interpreter.

[Raphael Reitzig]

Yup, ANTLRWorks' interpreter is (today) not capable of predicate  
evaluation. Use debugging.

Regards

Raphael

"Peter C. Chapin" <pcc482719 at gmail.com> wrote (Thu Jul 31 12:58:29 2008):

> rkevinburton at charter.net wrote:
>
>> I don't know if this will help but I have found that the output  
>> changes based on the line ending selected (Unix(LF) or MS(CR LF).
>>
>
> I tried playing with that setting but it didn't seem to make any difference.
>
> Today I tried interpreting just 'A' (a bare identifier) as a  
> 'primary_expression' instead of as an expression. In that case I get  
> a  FailedPredicateException instead of a NoViableAltException. So  
> that does make it sound like the issue is related to backtracking  
> (keep in mind that these failures only seem to occur in the  
> ANTLRworks interpreter).
>
> Thanks for your suggestion!
>
> Peter
>
>>> Hello!
>>>
>>> I'm using ANTLRworks 1.1.7 and I'm building a grammar for a C-like  
>>> language. I've created some unit tests for my grammar...  
>>> specifically a collection of files containing text that is  
>>> intended to be syntactically correct. My test program loops over  
>>> these files, instantiates a parser for each (one at a time), and  
>>> tries to parse them all. I use various start symbols to exercise  
>>> parts of the grammar incrementally in these tests (helps to  
>>> isolate errors).
>>>
>>> So, given a file containing just
>>>
>>> A = B
>>>
>>> my test program successfully parses this using a start symbol of  
>>> 'expresion.' This is fine. However, when I use the ANTLRworks  
>>> interpreter and enter the text 'A = B' I get a  
>>> 'NoViableAltException.' I noticed that the interpreter is ignoring  
>>> my WHITSPACE rule so I removed the white space from the text  
>>> (using 'A=B') but that didn't help. In fact, the interpreter  
>>> produces a NoViableAltException even when I just use 'A' as input  
>>> text. However, a bare identifier is a valid expression in my  
>>> target language (and it parses fine when using the test program I  
>>> described above).
>>>
>>> I'm think I am missing something fundamental about how the  
>>> interpreter is supposed to work. I'm hoping someone can set my  
>>> feet upon the path of enlightenment! I did check the on-line  
>>> ANTLRworks user's guide, but the section on the interpreter  
>>> doesn't shed much light on my question.
>>>
>>> P.S. I do have backtracking mode turned on right now in my  
>>> grammar's option. Could that have something to do with it?
>>>
>>> Peter
>>>
>



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