[antlr-interest] Re: nice threads
Brian Smith
brian-l-smith at uiowa.edu
Fri Jun 14 13:03:39 PDT 2002
Terence Parr wrote:
>>Is grammar subclassing still appropriate?
>
> I think it should be a function of the environment. I.e, have a library
> of rules/grammars in your repository and then pick and choose stuff to
> grab to begin a new grammar. A live push-forward-changes sort of thing
> is the same as inheritance ;) (I think they call that RCS) ;) ;)
I think that what is needed is a "rule import" mechanism, instead of
subclassing. If you did this, then I could import rules from more than
one grammar and do so selectively. Also, my parser could import all the
rules from my lexer, and then when I run my parser grammer through ANTLR
it can actually tell me which lexer rules I forgot at code-generation
time, instead of me having to figure it out at runtime.
>>When I think about grammars and aspects I think actions--AspectANTLR
>>would
>>be the tool to weave your actions into your pure antlr grammars. The
>>trick
> Oooooooohhhhhh. Now THAT is the perfect explanation of what an Aspect
> is. You don't want to modify a grammar physically just to add actions
> into the right spot!. Oohhhh.
But, how do you specify the joinpoints? Wouldn't you use the grammar
rules as the join-points? If so, then you really haven't gained anything.
Have you looked at SableCC? They don't allow you to put any rules into
your grammar. Instead, they automatically generate a bunch of classes
that represent a heterogeneous AST. Then you subclass these generated
classes to include your code.
- Brian
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