On Wed, Jan 7, 2009 at 12:46 AM, David Abrahams <dave@boostpro.com> wrote:
on Tue Jan 06 2009, Arno Schödl <aschoedl-AT-think-cell.com> wrote:
It seems to me that the standard should specify whether iterator::reference must outlive its iterator. That's a separate issue. It doesn't.
I am confused. As far as I understand, Bo Persson just posted that this has been clarified:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2807.html#198
I see, yes, for the next standard.
So reference/pointer do not outlive their iterator, and in our case, boost::counting_iterator is correct and boost::reverse_iterator is wrong.
With respect to C++0x, that's correct.
I wonder if this means we really are missing an important concept. It seems to me that the requirement to store a temporary iterator is a potentially high cost that can be avoided for most iterators, which have persistent referents.
I also wondered about this. Since this is often a problem when composing iterators, perhaps for the iterators we have control of we could have the reference type as a template parameter. This would be much like the iterator adaptor and facade code. Then perhaps it's possible to use a type generator to generate the appropriate result type based on the combination of iterators? I really haven't thought this through so I'm ready for the flaws and obvious errors to be pointed out! I hope this helps, but apologise if it ends up being just spam. Neil Groves
-- Dave Abrahams BoostPro Computing http://www.boostpro.com _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost