From: Achim Gratz <Stromeko@nexgo.de>
To: emacs-orgmode@gnu.org
Subject: Re: GSoC 2012 -- Elisp backend for Ragel
Date: Wed, 28 Mar 2012 08:34:43 +0200 [thread overview]
Message-ID: <87bonhkzcs.fsf@Rainer.invalid> (raw)
In-Reply-To: CA+5B0FNeMOGrbUYDYkn50cxQX7UEfh5KkeaZhOZTfozji3=zJQ@mail.gmail.com
Aurélien Aptel <aurelien.aptel@gmail.com> writes:
> Ragel is written in C++ and has no dependency.
It depends on having a working C++ compiler (presumably with some list
of features / standard conformance).
> * every major platform has a C++ compiler
Yes, but it may not be installed. Or has the wrong version. Or
whatever.
> * ragel input along with generated code can be tracked in the repo
It is a bad idea(TM) to track both the sources and the result of a
generation from that source in the same repo. That other projects are
doing that doesn't mean we should follow their example.
> * the generated code is portable since it's elisp (doesn't need to be
> regenerated on different platforms)
> * the parser is a confined part of org-mode
>
> I don't think this is a problem.
It may not be a problem for you. It probably isn't for me. I'm still
not saying it won't be a problem for every org-mode user. You need to
think about possible problems from the user perspective.
>> Which is just as easily done by specifying the syntax incorrectly.
>
> I think the fix will be shorter and simpler in the syntax because it's
> easier to reason on an abstract definition when it comes to language.
> When you're neck-deep in your handwritten implementation trying to
> figure what you did wrong, it can take a long time.
Please have a look at Nicolas' code first before making such statements.
I haven't seen ragel output, especially not in ELisp and I don't know
how easy it will be to debug parse errors. The other thing to keep in
mind is that org-mode doesn't have a formal syntax description, much
less one that follows one of the standard grammars. This will be a much
bigger fish to fry then
>> No, you can (for a suitably restricted set of languages) formally proof
>> that the implementation and the specification is identical for any
>> input.
>
> How would you do that programmatically?
Fundamentally? By induction.
>> The assumption that an FSM running in ELisp is faster than a bunch of
>> regexp has not been actually tested or has it?
>
> I haven't tested anything yet.
> If I remember correctly, the emacs regex API doesn't provide a way to
> compile patterns and thus have to be compiled at each call.
I haven't checked. But all this happens in machine code, not ELisp, so
it is not clear on whether a re-implementation of the regex engine, even
if it is vastly superior to the one Emacs uses now would be a net win.
> Also the underlying FSM implementation uses NFA which can lead to a
> exponential complexity in time [1] for certain patterns.
That trait is shared by all regex engines that allow backreferences.
Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
SD adaptations for KORG EX-800 and Poly-800MkII V0.9:
http://Synth.Stromeko.net/Downloads.html#KorgSDada
next prev parent reply other threads:[~2012-03-28 6:35 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-22 13:43 GSoC 2012 -- Elisp backend for Ragel Rustom Mody
2012-03-23 11:12 ` Aurélien Aptel
2012-03-23 11:36 ` Rustom Mody
[not found] ` <CAJ+TeoebkVTLs9nrDTH_6xvzvkk1vTEZDL2iHmEAkTUfZRjpjQ@mail.gmail.com>
[not found] ` <CAJ+TeoebkVTLs9nrDTH_6xvzvkk1vTEZDL2iHmEAkTUfZRjpjQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-03-25 4:17 ` Rustom Mody
2012-03-25 6:55 ` Rustom Mody
2012-03-25 10:06 ` Aurélien Aptel
2012-03-25 11:40 ` Nicolas Goaziou
2012-03-25 12:52 ` Martyn Jago
2012-03-27 20:34 ` Aurélien Aptel
2012-03-27 21:22 ` Achim Gratz
2012-03-27 22:11 ` Aurélien Aptel
2012-03-28 6:34 ` Achim Gratz [this message]
2012-03-29 17:50 ` Aurélien Aptel
2012-03-29 17:52 ` Samuel Wales
2012-03-29 19:04 ` Achim Gratz
[not found] ` <87vclsykl6.fsf-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2012-03-27 20:03 ` Aurélien Aptel
2012-03-26 16:01 ` Bastien
[not found] ` <87wr674aii.fsf-mXXj517/zsQ@public.gmane.org>
2012-03-27 20:49 ` Aurélien Aptel
2012-03-27 22:10 ` Bastien
2012-03-26 15:53 ` Bastien
-- strict thread matches above, loose matches on Subject: below --
2012-03-21 18:51 Aurélien Aptel
2012-03-21 19:32 ` Aurélien Aptel
2012-03-21 19:34 ` Samuel Wales
2012-03-22 12:22 ` Thorsten
2012-03-24 8:16 ` Nicolas Goaziou
2012-03-26 16:03 ` Bastien
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