> <[1]
alyn.post@lodockikumazvati.org> wrote:
>
> On Tue, Nov 23, 2010 at 10:52:11AM -0800, Robin Lee Powell wrote:
> > On Tue, Nov 23, 2010 at 11:43:52AM -0700, .alyn.post. wrote:
> > > What does the following production in the lojban grammar mean?:
> > >
> > > rp-_expression_-tail <- rp-_expression_ operator rp-_expression_-tail /
> > > ()
> > >
> > > Do I understand that to mean 'the sequence of rp-_expression_,
> > > operator, and rp-_expression_-tail OR nothing?' Could the above
> > > also be expressed:
> > >
> > > rp-_expression_-tail <- (rp-_expression_ operator rp-_expression_-tail)?
> > >
> > > And if so, why the odd way of specifying it? I'm weak on pitfalls
> > > of recursive behavior in grammars, am I looking at a workaround
> > > related to that?
> >
> > Yes, and it mostly doesn't work. Lojban's RPN (which, if I have my
> > druthers, the next version of the language will not have, by the
> > way) is left-recursive, which is problematic. See the peg mailing
> > list for various solutions, but IMO since a number of PEG parser
> > generators handle this on their own, I think we should just have it
> > be left-recursive and say that people have to use such a generator.
> >
> > If you can figure out how to fix it in in the rules so the right
> > behaviour pops out, though, *please* do so. There are links to
> > papers on the peg mailing list; it came up just last week; "*[1]*
> > *Packrat Parsers Can Support Left Recursion*, Alessandro Warth,
> > James R. Douglass, and Todd Millstein (2008)" is the citation I'm
> > seeing at a brief glance.
> >
>
> Great. I saw that thread and ignored it as not being relevant in
> the moment, but I'm happy to read it and play with it when I get to
> that point.
>
> I've downloaded the paper and cached it with this problem, as I'm a
> bit ahead of myself with it.
> -Alan
> --
> .i ko djuno fi le do sevzi
>
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