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Re: [O] GSoC 2012 -- Elisp backend for Ragel
From: |
Achim Gratz |
Subject: |
Re: [O] GSoC 2012 -- Elisp backend for Ragel |
Date: |
Wed, 28 Mar 2012 08:34:43 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.0.94 (gnu/linux) |
Aurélien Aptel <address@hidden> 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.
--
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SD adaptations for KORG EX-800 and Poly-800MkII V0.9:
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- Re: [O] GSoC 2012 -- Elisp backend for Ragel, (continued)
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/23
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Rustom Mody, 2012/03/23
- Message not available
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Rustom Mody, 2012/03/25
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Rustom Mody, 2012/03/25
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/25
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Nicolas Goaziou, 2012/03/25
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Martyn Jago, 2012/03/25
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/27
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Achim Gratz, 2012/03/27
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/27
- Re: [O] GSoC 2012 -- Elisp backend for Ragel,
Achim Gratz <=
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/29
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Samuel Wales, 2012/03/29
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Achim Gratz, 2012/03/29
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/27
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Bastien, 2012/03/26
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Aurélien Aptel, 2012/03/27
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Bastien, 2012/03/27
- Re: [O] GSoC 2012 -- Elisp backend for Ragel, Bastien, 2012/03/26