Re: [boost] [mpl]iter_fold_if Forward Backward rationale?

Subject: Re: [boost] [mpl]iter_fold_if Forward Backward rationale?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2009-04-25 09:15:57

On 04/22/09 11:19, Larry Evans wrote:
> On 04/21/09 11:36, Larry Evans wrote:
>  > On 04/15/09 11:39, Larry Evans wrote:
> [snip]
> 
>  >  > The following zip file in the vault's variadic_template directory:
>  >  >
>  >  >   http://preview.tinyurl.com/c6h7vc
>  >  >
[snip]

> There's now in the same vault directory, while.cpp.  This demonstrates
> how a while_ template can be used with an explicit stack to avoid the
> problems of iter_fold_if accessing the end iterator.  The exlicit
> stack is the 3ird parameter to:
> 
>   template
>     < typename Iter
>     , typename State
>     , typename Stack
>     >
>   struct forward_state
>   ;
> 
> This stack is built up during the 1st while_ instantiation and then
> that stack is traversed during the 2nd while_ instantiation. 
[snip]

However, the if_recur template attached to a previous post:

   http://article.gmane.org/gmane.comp.lib.boost.devel/188322

could be used to accomplish the same task.  The Else parameter
to if_recur could be another ir_recur.  The outer if_recur
would perform the task of the 1st while (building up the
stack as well as building the state) and the Else if_recur
would perform the task of the 2nd while.

At least I think so.  I haven't tried it yet.

Is there any interest?

-regards,
Larry