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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