I was struggling with const correctness and iterator adaptors. At first I was using iterator_facade. I found it difficult to get dereference to work correctly. After changing to iterator_adaptor I got things working. I'm wondering if the approach I used is "correct". I include the whole class here, because it isn't really very big. I was using a Ring class which contains an iterator, which is cycle_iterator<std::vector<Complex>::iterator>. If a Ring const& is passed I had problems with dereference. The changes I made to cycle_iterator fix this were: 1) Add templated conversion constructor to cycle_iterator, to allow implicit conversion of cycle_iterator -> const cycle_iterator. 2) Include both reference dereference() and const reference dereference() const (likewise for operator[]) So, do my changes constitute a "correct" approach to making interoperable iterators using boost::iterator_adaptor?