[antlr-interest] lexical nondeterminism between IDENT & LABEL

Monty Zukowski monty at codetransform.com
Wed Nov 3 12:17:30 PST 2004


On Nov 3, 2004, at 9:49 AM, John D. Mitchell wrote:

>
>>>>>> "thoth2487" == thoth2487  <thoth2487 at libero.it> writes:
> [...]
>
>> Hi to all, I've a very simple language in which there are IDENTifiers 
>> and
>> jump LABELs. An IDENTifier start with ('a'...'z')|('A'..'Z') and 
>> continue
>> with ('a'...'z')|('A'..'Z')|('0'..'9') and a LABEL is like an 
>> IDENTifier
>> but ends with a ':'. When I try following .g I obtain always a lexical
>> nondeterminsim which I isn't to solve:
>
> Stop trying to do that in the lexer.  Let the lexer return the ID for 
> both
> and then have your parsing rules distinguish between ID ":" being a 
> label
> or the ID is just an ID.
>


Some languages like AREV are made much simpler if the lexer can 
distinguish labels from IDs, that was the whole inspiration for my 
ParserFilter example on my website.

Monty

ANTLR & Java Consultant -- http://www.codetransform.com
ANSI C/GCC transformation toolkit -- 
http://www.codetransform.com/gcc.html
Embrace the Decay -- http://www.codetransform.com/EmbraceDecay.html



 
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