[antlr-interest] SableCC tree stuff (Was: Antlr 3.0 spaces between tokens)

[Alexey Demakov]

From: "Terence Parr" <parrt at cs.usfca.edu>
> Anyway, I'm off to Montreal to meet with Etienne Gagnon the SableCC  
> guy; giving a talk tomorrow.  Racing off to the airport in a few  
> minutes so I'm afraid I won't be able to contribute much until I get  
> back on Sunday.  Damn, this discussion and the one on trees is getting  
> interesting!  You can be sure I'll be figuring out his tree visitor  
> generation stuff (like TreeDL?).

I'm playing with SableCC tree, visitors and walkers and can't agree
that generation of tree from grammar is good idea. Even if it is heterogenous
strictly-typed SableCC tree.
I don't like tree node repetition because of grammar conflict resolving.
See java grammar example:

AForStatement
AForStatementNoShortIF

or simple C:

AIfElseStatement
AIfStatement
AIfThenElseStatement

These nodes are the same logically. And three almost identical visit methods 
should be implemented instead of single one.

Another strange thing from simple C example:

ASignedCharSpecifier
ASignedCharTypeSpecifier
ASignedIntSignedIntSpecifier
ASignedIntTypeSpecifier
ASignedLongIntSignedLongSpecifier
ASignedLongSignedLongSpecifier
ASignedLongTypeSpecifier
ASignedShortIntSignedShortSpecifier
ASignedShortSignedShortSpecifier
ASignedShortTypeSpecifier
ASignedSignedIntSpecifier

All of these modifiers can be set of flags in one node!

May be I don't understand SableCC very well, but if my notion
is adequate, SableCC trees are not very useful.

TreeDL now provides tree structure description and generation of:
- tree node class
- visitor interface and some basic visitors implementations
- depth-first tree walker (implemented, but not released yet)
- new features that can be added as plugins very easy.

and the only drawback I see - manual tree construction in parser.

May be sometimes in the future if TreeDL will be used by community,
construction of TreeDL trees will be implemented in ANTLR :)

Regards,
Alexey

-----
Alexey Demakov
TreeDL: Tree Description Language: http://treedl.sourceforge.net
RedVerst Group: http://www.unitesk.com




 
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