Yes, that plus correctly ignoring {'s and }' that appear in strings
since those can be unbalanced. My rambling earlier was a long way of
saying that something simple like this is all that is necessary.
- Tom
On Jul 24, 11:37 pm, Nathan Weizenbaum <[EMAIL PROTECTED]> wrote:
> Really, all we'd need to do to get the tag working is to have an
> extract_attributes method that grabs everything between the first '{'
> and the balancing '}'.
>
> - Nathan
>
> Tom Bagby wrote:
> > Performance will probably deprove since the current naive regex
> > implementation does less work than is really necessary to parse
> > correctly. Also, templates are parsed only once, so parser
> > performance doesn't really matter much in the grand scheme of things.
>
> > I'm happy to see all proofs of concept, but I think an ANTLR parser is
> > probably overkill. In fact, a 'real parser' for most of Haml is
> > almost certainly overkill. I've been messing around with a relatively
> > simple ragel machine (http://www.cs.queensu.ca/~thurston/ragel/) just
> > for tag parsing. I think even that is too much. A simple 'real
> > parser' for tags written by hand would be quite short. It's probably
> > worth it to write it that way just to avoid dependencies on external
> > build tools/languages. But playing with parser toys is very fun.
>
> > Ever the pessimist,
> > Tom
>
> > On Jul 24, 11:23 am, Evgeny <[EMAIL PROTECTED]> wrote:
>
> >> I will try create a proof-of-concept ANTLR parser then.
> >> See how it goes. If filters are a show stopper, then perhaps there is
> >> a bit different way of creating them that will work better.
>
> >> For some reason I think performance might improve as well.
>
> >> Or perhaps I am just an optimist :)
>
> >> On 7/24/07, Nathan Weizenbaum <[EMAIL PROTECTED]> wrote:
>
> >>> Problem is, I'm pretty sure it's not a context-free grammar. I'm no
> >>> expert on parsing and state machines and such, but even if we got rid of
> >>> the indentation (which is how Python and I believe Yaml are parsed), I'm
> >>> pretty sure stuff like filters throws a big bone into everything. I
> >>> could be wrong, though...
>
> >>> Either way, it would certainly be possible to make a real parser at
> >>> least for tags.
>
> >>> - Nathan
>
> >>> Tom Stuart wrote:
>
> >>>> The general problem is more fundamental than that -- finite state
> >>>> machines (i.e. the programs encoded by regular expressions) lack the
> >>>> computational power to do unlimited parenthesis balancing -- but
> >>>> regardless, non-greedy matching will fail whenever parentheses are
> >>>> nested more than one level deep:
>
> >>>> %foo{:bar => { ... }}
>
> >>>> Here we'd match the first '{' with the first '}' (which isn't its
> >>>> partner) so it's just the opposite problem.
>
> >>>> I don't know off the top of my head whether people typically use
> >>>> nested hashes in tags, but in the general case they do.
>
> >>>> (A thousand beers to the person who rewrites Haml and Sass to use
> >>>> Ragel and a real parser.)
>
> >>>> Cheers,
> >>>> -Tom
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