Re: [boost] compressed_pair initialization

From: Joe Gottman (jgottman_at_[hidden])
Date: 2006-05-18 19:48:28

"David Abrahams" <dave_at_[hidden]> wrote in message 
news:uves3axtp.fsf_at_boost-consulting.com...
>
> I find myself creating this class member:
>
>      compressed_pair<
>          storage
>        , compressed_pair<
>              Lookup
>            , compressed_pair<
>                  GetUnstored
>                , SetUnstored
>              >
>          >
>      > members;
>
>
> I imagine this sort of usage is pretty common.  The problem is that
> it's hard to initialize this member efficiently: you have to build and
> copy too many compressed_pairs.  I propose to extend compressed_pair
> with overloaded ctors, as follows:
>
>   compressed_pair(
>        first_param_type f
>      , typename second_type::first_param_type sf
>      , typename second_type::second_param_type ss);
>
>   compressed_pair(
>        first_param_type f
>      , typename second_type::first_param_type sf
>      , typename second_type::second_type::first_param_type ssf
>      , typename second_type::second_type::second_param_type sss );
>
>   ...
>
> etc.
>
> If SFINAE doesn't take out these declarations when the second type is
> not a (compressed_)pair, we can always template them.
>
>
> Thoughts?

   The first thought that comes to my mind is that this situation cries out 
for a compressed_tuple class.  How difficult would it be to write one?

Joe Gottman