Re: [Boost-users] [fusion] named parameter technique with fusion::map

Subject: Re: [Boost-users] [fusion] named parameter technique with fusion::map
From: Larry Evans (cppljevans_at_[hidden])
Date: 2010-11-08 09:25:00

On 11/08/10 06:55, Larry Evans wrote:
[snip]
> Unfortunately, reversing args to airs_nam_ti1_3_t CTOR,
> as in:
> 
>       pairs_nam_ti1_3_t
>     pairs_nam_ti1_3_v
>     ( fusion::pair<mpl::int_<2>,ti<2> >(2)
>     , fusion::pair<mpl::int_<1>,ti<1> >(1)
>     )
> 
> causes compile error about "no matching function".
> 
> Investigating.

Problem solved By adding a templated member function, put, to
pairs_named template.

Also, renamed overloaded arg function to at_key, since that's
more descriptive.

> 
> -Larry
> 
> BTW, just read:
> 
>   http://www.boost.org/doc/libs/1_44_0/libs/fusion/doc/html
>     /fusion/notes.html#fusion.notes.overloaded_functions
> 
> which says:
> 
>   There is an overloaded function, f(k), for each key type k.
>   The compiler chooses the appropriate function given a key, k.
> 
> which is exactly the method used in named_component_ctor.cpp,
> where the overloaded function is arg.

It's not obvious to me, after looking at:

  key_of_impl.hpp
  value_of_impl.hpp

in boost/fusion/container/map/detail where this overloaded
function, f, is located.  (Of course I assume it's not named
f, but something like value_of...).  Could someone point it out?

TIA.

-Larry