[boost] Re: [iterator_facade] postfix ++/--

From: David Abrahams (dave_at_[hidden])
Date: 2004-07-11 22:18:07

David Abrahams <dave_at_[hidden]> writes:

> I'm getting ready to fix the issues we've discussed with postfix ++
> (and by extension, --) in iterator_facade.  Basically, the current
> implementation works for forward iterators but not for some input
> iterators:
>
>        {
>             self x = *this;
>             ++*this;   // <== here
>             return x;
>        }
>
> The problem is that for many input iterators, all copies reference the
> same element.  The marked line increments the iterator, which causes
> the current element of the sequence to be skipped, so
>
>     *a++
>
> yields the /next/ element.  To fix that, a++ needs to return a proxy
> type.

Fixed now in CVS, along with new tests.
-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com