[boost] Re: Userfriendly interaction of tuples with mpl containers

From: nee Spangenberg (dsp_at_[hidden])
Date: 2004-01-15 07:57:06

Hi Aleksey Gurtovoy,

Aleksey Gurtovoy schrieb:

>     template< typename Types > struct tuple_gen
>         : mpl::fold_backward<
>               Types
>             , boost::tuples::null_type
>             , boost::tuples::cons<_2,_1>
>             >
>     {
>     };
>
>     template<
>         typename T0 = boost::mpl::void_, typename T1 = boost::mpl::void_,
>         typename T2 = boost::mpl::void_, typename T3 = boost::mpl::void_,
>         typename T4 = boost::mpl::void_, typename T5 = boost::mpl::void_,
>         typename T6 = boost::mpl::void_, typename T7 = boost::mpl::void_,
>         typename T8 = boost::mpl::void_, typename T9 = boost::mpl::void_
>         >
>     class Test
>     {
>         typedef mpl::vector<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9> types_;
>
>         typedef typename tuple_gen<
>               mpl::filter_view<
>                   types_
>                 , mpl::not_< mpl::is_void_<_1> >
>                 >
>             >::type Tuples;
>
>         Tuples m_Tuple;
>     };

Great - thank you very much, Aleksey! I will try it using a newer boost lib as
which I am currently forced to use (1.30) and MSVC6, where I get the the following
error

e:\download\source\c++\boost\unpacked\boost_1_30_0\boost\mpl\aux_\preprocessed\msvc60\apply.hpp(86):
error C2039: 'apply': is not a member of 'f_<0>'

e:\download\source\c++\boost\unpacked\boost_1_30_0\boost\mpl\aux_\preprocessed\msvc60\apply.hpp(100):
see reference to class template instantiation
'boost::mpl::aux::msvc_apply2<boost::tuples::cons<boost::mpl::arg<2>,boost::mpl::arg<1>>>::re

sult_<boost::tuples::null_type,A>' being compiled

(MSVC 7 worked with 1.30, btw, but I am not allowed to use it here)

> Joel de Guzman's Fusion library (http://tinyurl.com/yvxzm) has the one that
> is about to replace the current implementation, and much more. In general,
> Fusion is definitely a must use tool if you are doing anything more than a
> very basic metaprogramming with tuples.

Thanks for that link! I really think, these are the right directions to go!

In deep dept,

Daniel