Lexer and parser generators using CTFE
a at a.a
Wed Feb 29 10:11:28 PST 2012
"Andrei Alexandrescu" <SeeWebsiteForEmail at erdani.org> wrote in message
news:jilnjg$1eu9$3 at digitalmars.com...
> On 2/29/12 11:15 AM, Nick Sabalausky wrote:
>> "Andrei Alexandrescu"<SeeWebsiteForEmail at erdani.org> wrote in message
>> news:jiljsg$193s$1 at digitalmars.com...
>>> On 2/28/12 1:52 PM, Dmitry Olshansky wrote:
>>>> - have reasonable compile times and memory consumption (though it will
>>>> only improve over time)
>>> Yes. I guess PEGs have problems there.
>> Probably LR, too, unless you build the state tables in a separate prior
>> build step.
> It's been a while since I read about PEGs (the packrat parser paper), but
> think it's a more fundamental issue with PEGs because they need to memoize
> several possible parses of the input.
I don't know much about packrat parsers, but what I meant is that generating
LALR tables (which are then used by an LALR parser) can be very
computationally expensive: For simple grammars, it's trivial, but for more
complex "typical programming langauge" grammars, it can easily take upwards
of quite a few minutes when *not* done in CTFE (at least on my underpowered
machine). Although maybe my implementation and GOLD's implementation both
just have some additional hidden scaling issue that isn't inherent to the
Actually using an *already*-generated LALR table (which only needs to be
generated once per grammar, not once per input) to parse doesn't have major
inherent efficiency issues compared to other parsing algorithms, AFAIK.
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