Hi boost, The filter_iterator as implemented disallows creating iterators via reference-to-base, as it requires its Predicate objects to be copy-constructible. This is a problem for a class that is passed a ref to a predicate from elsewhere. It's a very easy fix, though, I'm wondering what the rationale originally was for the restriction. If it isn't significant, I'd propose the change below, as (at least from my narrow perspective) it is a big plus to be able to do this. 56c56 < filter_iterator(Predicate& f, Iterator x, Iterator end = Iterator()) ---
filter_iterator(Predicate f, Iterator x, Iterator end = Iterator())
82c82 < const Predicate& predicate() const { return m_predicate; } ---
Predicate predicate() const { return m_predicate; }
106c106 < Predicate& m_predicate; ---
Predicate m_predicate;
112c112 < make_filter_iterator(Predicate& f, Iterator x, Iterator end = Iterator()) ---
make_filter_iterator(Predicate f, Iterator x, Iterator end = Iterator())
Thanks for your time, -t