Good luck, this is one of my favourite topics ;)

There is a recent new animal called Parse::Eyapp which deserves having a look. Also Manning has released recently a book on the subject of parsing with Perl.

Would be nice to have a review of table-driven top-down parsing and possible speed advantage of (almost)infinite backtracking: look at packrat parsing in Wikipedia and google for SLK, and then you could tell us how to do a fast version of Parse::RecDescent, and if you start the project maybe i'll even help you ;).

PPI has some interesting comments in its doc about parsing in general. It would be really nice to have a survey of the various techniques used in the various sucessful parsers written in Perl (even the ones with C parts) so that it could be extrapolated a useful set of rules for a generic useful (fast, easy to use) parser generator .

Another interesting line of thought is "chunk parsing" and give the illusion of "stream" regexes. Obviously what is needed is a smart tokenizer. One simple approach is to have various chunk levels, you drive a simple m//gc regex-based lexer with a small chunk (string); if match you add chunk to have always minimum length and if no-match you add it another chunk and some kind of heuristics which enable switching to something faster if parsing comment-like or quotish-like (pretokenizing on big chunks)...some ideas can be taken from IO::Tokenizer, IO::Mark and the such

Congratulations for the topic and the interesting outline.
I look forward for the talk.

Thank you Stephan for mentioning Parse::Eyapp. I thought none paid previously attention to it :-(

Parse::Eyapp is fully compatible with Parse::Yapp. It fixes a few bugs that were in Parse::Yapp and -sure - it introduces new ones :-)

Furthermore, Parse::Eyapp extends Parse::Yapp with concepts similar to those found in Parse::RecDescent: autoactions, automatic generation of trees, etc.

There are, however, a few new functionalities: Translation Schemes and a Tree Transformation language to mention two.

If you need any assistance with the module I will be more than glad to help. Have a look at the examples directory inside the distribution. Also, there is a brief tutorial at

http://nereida.deioc.ull.es/~pl/eyapsimple/

The source code for this tutorial can be found at

http://nereida.deioc.ull.es/~pl/eyapsimple/source.tgz Best

Casiano

Thanks for your suggestions. I'll definitely be taking some of them on board. In regard to your comment about smart tokenising, I have a sort of negatively-matching lexer for that I call the antilexer which I might include but only if it survives as a sensible alternative after CPAN modules have been thorughly investigated.

For large continuous streams and such-like where I can't use the usual module, I use instance variables that have rules, recursion depths at which to start building trees, callback functions definable as "parser exits" (that's something I picked up from old prePerl technoliogy) to be invoked at certain points so that the tree never needs to be completed but can be acted on or code generated on the fly and I am sure there are other special needs situations I haven;t yet thought of!

It's a horrible minefield but I love it too ;);) after all - if the subject were reducible to bolting modules together and that working for every case, it wouldn't be so interesting, would it?

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^M Free your mind!

...More thoughts...

There is a new edition of the book by Grune et al Parsing Techniques. It should be out or close.

Often people think about LR or LL parsing but the first edition of "Parsing Techniques" talks about starting anywhere! which is interesting at least in the sense of having maybe two-staged tokenizing <chess>?!</chess>

then there is HOP::Lexer. I haven't played much but it is quite slower than anything based on Parse::Yapp. Still a mixed approach could be nice...

finally using 5.9.x or more one can plug a different regexp engine, say a small one that permits "streaming"

Update: [SDF] seems also interesting.

cheers --stephan

I'll have the slides ready in a few weeks in a mail-sendable format, but I am not sure if it is right to put them online - people should have to go to the conference to consume the material, shouldn't they? If significant conference material were available online people might stay at home!

You wrote this twice, but he wrote: "I would appreciate it if you could provide a link to the presentation once it is finished." I'm pretty sure he meant after the conference. In any case reading a presentation and attending to it are quite different experiences: in many cases I find slides to be instructive, but without the accompanying speech much is lost. So those who really want to be there will do in any case and there are also quite a lot of people that won't come anyway, maybe because they live abroad.

OK I see your point - I'll review the matter after the conference.
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Thanks for the clarification - I'll review exactly what to publish soon after the conference - In particular I'll need to take a decision on whether to go for a more detailed publication or not at that point, a talk being rather different from written-only.
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^M Free your mind!