[ragel-users] One question.

[Adrian Thurston]

It depends on the language being parsed. If it's easy to know when push 
and pop (because of the appearance of certain tokens) then you probably 
won't run into problems and it's just a matter of personal preference. 
If the language is more complicated than that (say like a programming 
language) then you are certainly going to get a headache trying to parse 
in ragel and you'll have to switch.

On 11-04-07 03:50 PM, Nate wrote:
> I've now done a couple projects with recursion using fcall. It isn't too
> bad. Is there something I lose by doing this, beyond the ability to
> express the recursion in Ragel? What would really make switch tools for
> a project?
>
> -Nate
>
>
> On Thu, Apr 7, 2011 at 1:22 PM, Adrian Thurston <thurston at complang.org
> <mailto:thurston at complang.org>> wrote:
>
>     To expand on this a bit ... it is entirely up to the user to manage
>     the stack allocation. Ragel's support for recursive structures
>     (fcall/fret) is an extension to the basic model, which is pure state
>     machine (not a PDA). If you find you have a lot recursion in what
>     you need to parse, you should consider that ragel might not be the
>     right tool for the job.
>
>     Regards
>
>
>     On 03/29/2011 09:59 PM, Nate wrote:
>
>         Yes, see the int[] stack in the link. :) Also note the code
>         under "prepush".
>
>         -Nate
>
>
>         On Tue, Mar 29, 2011 at 9:38 PM, Gordeev Vladimir
>         <gordeev.vladimir.v at gmail.com
>         <mailto:gordeev.vladimir.v at gmail.com>
>         <mailto:gordeev.vladimir.v at gmail.com
>         <mailto:gordeev.vladimir.v at gmail.com>>> wrote:
>
>             Hm, this looks like solution. I will try it. Thanks.
>
>             Related question: Does Ragel have some inner stack to handle
>         nested
>             fcall/fret?
>
>
>             On 30.03.2011 00:59, Nate wrote:
>
>                 You can use fcall to jump to a machine, then fret to
>             resume where
>                 you were. It's a bit tricky, but once you understand it
>             you can
>                 parse recursively. See the startTable action here
>             (though this is
>                 a pretty hairy parser):
>             http://code.google.com/p/table-layout/source/browse/trunk/build/TableLayoutParser.rl
>
>                 -Nate
>
>
>                 On Tue, Mar 29, 2011 at 2:55 PM, Jonathan Castello
>             <twisolar at gmail.com <mailto:twisolar at gmail.com>
>             <mailto:twisolar at gmail.com <mailto:twisolar at gmail.com>>> wrote:
>
>                     On Tue, Mar 29, 2011 at 1:15 PM, Gordeev Vladimir
>             <gordeev.vladimir.v at gmail.com
>             <mailto:gordeev.vladimir.v at gmail.com>
>             <mailto:gordeev.vladimir.v at gmail.com
>             <mailto:gordeev.vladimir.v at gmail.com>>> wrote:
>              > So I got following error:
>              >
>              >     test.rl:7:32: graph lookup of "list" failed
>
>                     The reason you get that error is because a rule can
>             only reference
>                     definitions that came before it. "list" doesn't
>             exist until the
>                     definition is finished, so it can't reference
>             itself. (That would
>                     create a recursive structure anyways, which Ragel isn't
>                     equipped to
>                     handle natively.)
>
>                     ~Jonathan
>
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>     --
>     Adrian D. Thurston
>     http://www.complang.org/thurston/
>
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-- 
Dr. Adrian D. Thurston
http://www.complang.org/thurston/

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