on Sat Dec 27 2008, Steven Watanabe <watanabesj-AT-gmail.com> wrote:
AMDG
David Abrahams wrote:
- transform_iterator.hpp - ...
for the various partition_point overloads?
Something like that seems likely. I'm still having trouble understanding how you can implement a specialization for transform_iterator without knowing more than actually possible about the semantics of the transformation function.
I think the idea is that if an optimized partition_point exists for the underlying iterator, the partition_point specialization for transform_iterator should use it. This has nothing to do with the specific transformation function.
Sorry, I still don't get it. Here's the declaration of partition_point as given by www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2666.pdf: template <class ForwardIterator, class Predicate> ForwardIterator partition_point( ForwardIterator first, ForwardIterator last, Predicate pred); Let's say ForwardIterator is a transform_iterator whose transformation function is f(x) => x >= 5 ? 1 : 0 and the underlying sequence is 0 1 2 3 4 5 6 7 8 9 so the transformed sequence is 0 0 0 0 0 1 1 1 1 1 and pred is p(x) => x < 1 How will the specialization of partition_point for transform_iterator come up with a predicate to pass on to the partition_point that applies to the underlying iterator type? In general, it can't reverse engineer the transformation function and figure out how to get from p(x) above to p'(y) => y < 5 can it? -- Dave Abrahams BoostPro Computing http://www.boostpro.com