Proto for Boost mailing list page: Re: [proto] : Proto transform with state

Subject: Re: [proto] : Proto transform with state
From: Eric Niebler (eric_at_[hidden])
Date: 2011-01-29 07:49:33

On 11/18/2010 4:56 AM, Eric Niebler wrote:
> I think Proto transforms need a "let" statement for storing intermediate
> results. Maybe something like this:
> 
>   struct RenumberFun
>     : proto::fold<
>           _
>         , make_pair(fusion::vector0<>(), proto::_state)
>         , let<
>               _a( Renumber(_, second(proto::_state))> )
>             , make_pair(
>                   push_back(
>                       first(proto::_state)
>                     , first(_a)
>                   )
>                 , second(_a)
>               )
>           >
>       >
>   {};
> 
> I haven't a clue how this would be implemented.
> 
> It's fun to think about this stuff, but I wish it actually payed the bills.

Bills be damned. I just committed to trunk an implementation of
proto::let, along with tests and reference docs. End-user docs are still
todo.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com