Re: [boost] [review] Fusion review, finalization

From: Joel de Guzman (joel_at_[hidden])
Date: 2006-05-12 01:47:28

Tobias Schwinger wrote:

> 1. How to set up the client namespaces most conveniently? 
> 
>    Too many qualified names clutter my code.
> 
>    I actually like the scheme the library uses but I encountered following 
>    portability problems on the client side:
> 
>     namespace a_scope
>     {
>       using namespace boost::fusion;
>       namespace result_of { using namespace boost::fusion::result_of; }
> 
>       namespace mpl = boost::mpl;
> 
>       struct a_copy_function; // omitted for transparency
> 
>       namespace result_of
>       {
>         template<typename Seq> struct noop_transform
>           : transform<typename boost::add_const<Seq>::type, a_copy_function>
>         //  ^^^^^^^^^ vc 7.1 and gcc 3.4 choke here
>         { };
>       }
> 
>       template<typename Seq>
>       inline typename result_of::noop_transform<Seq>::type
>       //              ^^^^^^^^^ found ambiguous by some compilers
>       // (IIRC it was gcc, couldn't reproduce the case, though)
>       noop_transform(Seq const & seq)
>       {
>         return transform(seq, an_identity_function());
>         //     ^^^^^^^^^ found ambiguous by vc 8 (visible + ADL)
>       }
>    }

Again, I'm not sure about the best use practice. On the client side,
I would think that you will want to use Fusion, MPL, interspersed with
STL. Those libraries (esecially MPL and Fusion) have lots of names
in common. I am not sure if using directives/declarations will be
practical at all. The least I can suggest is:

     namespace mpl = boost::mpl;
     namespace fusion = boost::fusion;

Those are short prefixes already. Or maybe even:

    namespace fpl = boost::fusion; // fusion programming library. hah! :)
    namespace bfl = boost::fusion; // boost fusion library. hahah! :)

Choose your pick. I kinda like the "fpl" synonym. It jives well with
mpl and stl.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net