Re: [boost] [GSoC][MPL11] Post C++Now update

Subject: Re: [boost] [GSoC][MPL11] Post C++Now update
From: Joel de Guzman (djowel_at_[hidden])
Date: 2014-05-18 18:35:31

On 5/19/14, 4:41 AM, Louis Dionne wrote:
> After discussing the issue several times during the week, I (and others)
> think it might be possible to merge Fusion and the MPL into a single
> library. I am currently trying to write a library that does that. Since
> this constitutes a large reorientation, I created a new repository which
> is available at [2]. Those with interest should consider subscribing to
> the repository to be updated as I make progress.

Been there tried that...

This has been proposed several times in the past. I reiterate my
position: MPL and Fusion are different beasts and it is not good for
both to be merged (if it is at all possible). MPL does not have the
runtime components that Fusion needs and Fusion has runtime
components that MPL *does not* need.

Also, because of the runtime aspects of Fusion, the semantics of
algorithms do not make sense in MPL. Take the any algo for example:

    http://tinyurl.com/mk2whdo

Note that odd in that example is a runtime operation. How do you
unite that? It works only with fusion sequences (with values)
and not with MPL sequences (with types). In MPL, that would be a
type-only predicate.

If you add values to MPL, it would be 1) unnecessarily more complex
than it needs to be and 2) the feature set would be comprised of very
ugly mongrels.

Regards,
-- 
Joel de Guzman
http://www.ciere.com
http://boost-spirit.com
http://www.cycfi.com/