[antlr-interest] Superclasses = best practise ...?

[Ranco Marcus]

Hi Jim,

Could you elaborate a bit on how you separate the logic from the grammar, especially when the grammar is supposed to target multiple languages?

To my knowledge, the only way of calling the logic is by adding an action to a rule { ... } and use the target language to call a method (in superclass, delegate, etc.). Because the grammar then contains the method call in the targeted language, the grammar is still not 100% language agnostic. 

What if we could somehow define join points in the grammar and have a mechanism to hook those up to code in the target (much like AOP)? Do you know if any attempts in this direction have been made in the past?

Best regards,

Ranco Marcus
Epirion Knowledge Solutions B.V.


> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Jim Idle
> Sent: Tuesday, May 24, 2011 6:42 PM
> To: antlr-interest at antlr.org
> Subject: Re: [antlr-interest] Superclasses = best practise ...?
> 
> I uses super classes to separate the grammar from the code - you can also
> use separate helper classes to do this too. I recommend keeping the logic out
> of the grammar, but if you have a smaller grammar and will never target
> other languages or want to reuse the grammar to do more than one task on
> the language, then you are not required to follow the Maven archetype.
> However, the lists of reasons not to put logic in with the grammar soon piles
> up.
> 
> Jim
> 
> > -----Original Message-----
> > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > bounces at antlr.org] On Behalf Of Hans-Juergen Rennau
> > Sent: Tuesday, May 24, 2011 1:14 AM
> > To: antlr-interest at antlr.org
> > Subject: [antlr-interest] Superclasses = best practise ...?
> >
> > Hello People,
> >
> > this is a question about best practices when augmenting lexer and
> > parser with Java code providing helper methods (or even inner classes
> > for storare purposes).
> >
> > The Maven prototype "antlr3-maven-archetype" creates example
> grammars
> > which use super classes (AbstractTParser and AbstractTLexer). The
> > comments in those super classes suggest to honour this as a general
> > pattern: put helper methods in a grammar base class in order to keep
> > the grammar light and clean. I think this has pros and a con. The con
> > is that this way the compactness of "all-in-one-unit" is sacrificed;
> > and reading the grammar one has to consult a second source. Also I
> > noted that the Definitive Guide never made any suggestions to employ
> > superclasses.
> >
> > So this is my question: would you recommend the superclass approach
> > indeed as the best practise, or rather regard it as a good practise
> > one might follow or not, perhaps depending on complexity?
> >
> > Thank you,
> >
> > cheers,
> >
> > -- Hans-Juergen Rennau
> >
> > List: http://www.antlr.org/mailman/listinfo/antlr-interest
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