Re: [boost] [GSoC] Helping out Phoenix v3

Subject: Re: [boost] [GSoC] Helping out Phoenix v3
From: Eric Niebler (eric_at_[hidden])
Date: 2010-05-04 15:51:37

On 5/4/2010 11:25 AM, Hartmut Kaiser wrote:
>> On 5/4/2010 4:37 AM, Hartmut Kaiser wrote:
>>>> Eric Niebler wrote:
>>>>> It's an open question whether it's desirable to hide the
>>>>> proto bits when exposing these customization points, and if
>>>>> so, what that would look like.
>>> 
>>> Even if I'm only remotely connected to this I would like to
>>> emphasize the importance of a simple extension interface. By
>>> 'simple' I mean: hide Proto! We do not need the full power of
>>> Proto here and forcing every user to understand Proto's fine
>>> details before he is able to write his own actor is not good.
>>> Yes, it is possible to hide Proto completely behind a set of
>>> well-crafted domain specific (i.e. Phoenix) interfaces. This has
>>> been done already in Spirit (V2) and has proven to work well.
>> 
>> Hartmut, where can I find the documentation for Spirit's
>> extensibility mechanism?
> 
> Ahem... There isn't any :-P  At least nothing complete. There are
> bits and pieces described in several places (like here:
> 
> http://www.boost.org/doc/libs/1_42_0/libs/spirit/doc/html/spirit/advanced/indepth/parsers_indepth.html
> 
> and here:
> 
> http://boost-spirit.com/home/articles/qi-example/creating-your-own-parser-component-for-spirit-qi/),
> 
> but nothing coherent yet.
> 
> You'll have to resolve to the source code for now, sorry.

That's OK. The extensibility mechanism for Phoenix is documented, and I
can make my own inferences. The challenge here will be to preserve the
strengths of a Proto-based design (a well-defined grammar against which
expressions can validated, and clean separation of data structure and
algorithm) with a clean extension mechanism. The Phoenix that we know
and love is clean and simple, but conflates data structure and
algorithm. That may not be an issue -- I can't think of alternate
algorithms for lambdas the way I can for parsers and regex engines. But
separation of data structure and algorithm is sound design, and I would
think twice before giving it up.

I foresee some long Phoenix hack sessions in Aspen next week.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com