[antlr-interest] Please help a newbie!

[Peter Ashford]

Peter Ashford wrote:

>Richard Clark wrote:
>
>  
>
>>Some of this just takes a Zen approach: becoming one with the 
>>documentation. Try adding # in front of the var names in the action 
>>(and look at the generated code to see what ANTLR does with it.)
>>
>>
>>assign
>> { float f; }
>>         : i:ID EQ f=f_expr                 { assignTo(#i->getText(), 
>>#f); }
>>         ;
>>
>> ...R
>>
>> 
>>
>>    
>>
>
>I appologise for being a pain - but adding the hash just makes the code 
>not compile because MSVC .NET thinks it's a preprocessor command.
>
>I have been stepping through the generated code and what I find is the 
>parser skipping over all of the possiblities (keywords, comments etc) 
>and throwing the no valid alternative exception rather than scanning as 
>an identifier
>
>
> 
>

I've got it!  The problem was my alpha class - I had

    protected
    ALPHA  : ('a'..'z'  'A'..'Z');

I should have had:

    protected
    ALPHA  : ('a'..'z' | 'A'..'Z');

And so identifiers ( ALPHA (ALPHA | DIGIT)*; ) weren't being matched 
because they didn't match the incorrect ALPHA pattern.

Richard - thanks very much for your help tracking this problem down.


 
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