[antlr-interest] Invalid parser generation

[Jim Idle]

Please don't email people directly - always use the list. Terence does not
have the time to answer generic questions about your grammar I am afraid,
unless you want to pay him :)

You really need to start by running all the example grammars until you
understand them, and reading the tutorials in the wiki.

Jim

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of mark4 at voila.fr
> Sent: Tuesday, September 04, 2012 7:00 AM
> To: Stefan Mätje; antlr-interest at antlr.org
> Subject: Re: [antlr-interest] Invalid parser generation
>
> Hi Stefan,
>
> Thanks for the info. The antlr.org website is down, so I couldn't delve
> into details about lexer and parser rules. What I understood from
> trials and errors is that ALL the lexer rules that are placed into the
> grammar are matched against input. But the COMPTE and ID rules are just
> parts of other rules. Tagging them as "fragment" seems to do the job by
> telling ANTLR not to match those rules taken alone. Now, the grammar
> validates and the generated code compiles.
>
> I'm using a ANTLRStringStream to input a string to be matched against
> the grammar. Now, when I execute the program, whatever string I may
> put, I never fall into the RecognitionException exception. I've asked
> Terrence whether the expression() method was the right method to run
> the parsing process (since in the ANTLR 3 C# tutorial, the method
> expr() was used but it's deprecated) but I did not get his reply yet.
> Note that I also had to change "HIDDEN" to "Hidden" for the code to
> compile. It seems that the tutorials are not up to date on the website.
>
> Regards,
> Mark
>
> > Message du 04/09/12 à 15h40
> > De : "Stefan Mätje"
> > A : antlr-interest at antlr.org
> > Copie à : "mark4 at voila.fr"
> > Objet : Re: [antlr-interest] Invalid parser generation
> >
> > Am 04.09.2012 14:35, schrieb mark4 at voila.fr:> Hi Stefan,
> > >
> > > Thanks for your reply. I didn't understand the difference between
> > > lexer rules and parser rules because, in fine, a parser rule will
> > > always resolve in a series of lexer rules...
> >
> > Please don't mix the lexer and the parser phase in your mind. The
> > lexer deals with single characters and groups them into tokens.
> >
> > The parser doesn't know anything about single characters and deals
> > only with tokens.
> >
> > > Anyway, I applied the modification but I now get an error:
> > >
> > > COMPTE : ('0'..'9')+;
> > >
> > > ID : ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')* ;
> > >
> > > The following token definitions can never be matched because prior
> > > tokens match the same input: COMPTE,ID
> >
> > You have rules in your grammar before COMPTE and ID that define a
> > superset of the character sequences that COMPTE and ID can match.
> >
> > > Well, I have several entities in my grammar that have different
> > > encoding forms, so how can I specify them one after the other?
> >
> > If at the end one type of token should be produced all needed regular
> > expressions have to go into one rule.
> >
> > > Thanks,
> > > Mark
> > >
> >
> > As rule of thumb write the most specific lexer rules first and then
> > follow them with the less specific rules. The lexer will give the
> > rules first written a higher precedence.
> >
> > So put your keywords first (which are fixed strings). Then follow
> them
> > with something like operators (also fixed strings). At the lower
> level
> > rules that can match different strings like ID and COMPTE follow.
> >
> > See what Antlrworks tells you about multiple matches and which rules
> > are involved.
> >
> > Don't know if this may help but the rule that matches both COMPTE and
> > ID would be most interesting.
> >
> > Best regards,
> > Stefan
> >
> > PS.: Please reply also to the list.
> >
> >
>
> ___________________________________________________________
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