<[EMAIL PROTECTED]> wrote: > Thomas Becker <[EMAIL PROTECTED]> writes: > > Unless I'm missing something, I believe that my > > original rough intuition was ok. Given my > combining > > iterator, it seems very easy to write your tuple > > iterator by providing a simple generic > > "reference-tuple-making" functional.
[...] > The returned tuple of references is not copyable > though --- the copies will > still refer to the originals. I went through all > this with my pair iterator; > try using std::sort on your pair of vectors, > especially with vectors of a > non-POD UDT with no swap specialization, just to > avoid any optimizations in > your standard library. A plain tuple-of-references > will screw up the vectors, > you need something more complex. > > Also, you can't use a tuple-of-references with input > iterators, since they > return values not references when dereferenced, so > you need to know the > iterator category and use a tuple of values in this > case. > > Finally, output iterators are even more bizarre, as > writing to the result of > dereferencing your combined output iterator needs to > write to the result of > dereferencing each of the individual output > iterators, and there is no telling > what type you get when you dereference an output > iterator. > I see now that with your tuple iterator, you are aiming much higher than I previously thought. Just like boost's transform iterators, my combining iterators are always and necessarily input iterators. (That's not really going to change under the new proposed iterator categories, although they'll help me.) I can cheat a little by returning a value that happens to hold a bunch of references, such as a boost::tuple of references. Nothing prevents me from doing that. But you want a parallel-iterator that one can, for example, pass to std::sort and have it order the underlying sequences lexicographically. That's a tall order. My combining iterator does not cover that. Neither do I think that my combining iterator is affected much by the ultimate solution to your problem. My combining iterator is a multi-dimensional boost::transforming_iterator. Yours would end up being a multi-dimensional boost::projection_iterator. That's a different colored horse. Thomas Becker Zephyr Associates, Inc. Zephyr Cove, NV [EMAIL PROTECTED] __________________________________________________ Do you Yahoo!? Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop! http://platinum.yahoo.com _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
