Re: [Boost-users] total noob help: LAMBDA with zip_iterator

From: David Abrahams (dave_at_[hidden])
Date: 2006-04-08 10:42:36

"chun ping wang" <cablepuff_at_[hidden]> writes:

>   std::for_each(
>            // iterate through (Need, Alloc, Finish).
>             boost::make_zip_iterator(boost::make_tuple(beg1, beg2, beg3)),
>             boost::make_zip_iterator(boost::make_tuple(end1, end2, end3)),
>            (
>                Parts where i wish to use lambda for abstraction .
>                 Assume:
>                   _1 = Need[i],
>                   _2 = Alloc[i],
>                   _3 = Finish[i],
>                  if (_1 == false && _3 <= Work)
>                 {
>                         _3 = true;
>                         Work += _2;
>                  }
>              ++var(ind)
>           )
>     );

Ah.  What you want is a way to wrap a lambda expression so that it accepts
a single tuple argument and exposes each element of the tuple to the
wrapped lambda expression as a separate argument.  It should be
possible, but we'll have to ask Jaakko and Gary for details.  I'm
pretty sure it's possible using Fusion and Spirit-2, but you'd need a
different version of zip_iterator.hpp (one that's checked in on a
branch of Boost's CVS).

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com