Hi, In MultiArray I would like use iterator_facade to create an iterator that can satisfy random_access_traversal, input_iterator_tag, and output_iterator_tag. I see that in the file boost/iterator/detail/facade_iterator_category.hpp, at line 138 there is a class in the boost::detail namespace declared template <class Category, class Traversal> struct iterator_category_with_traversal So it looks like passing: boost::detail::iterator_category_with_traversal<boost::detail::input_output_iterator_tag,boost::random_traversal_tag> as the CategoryOrTraversal would be what I want. However, two components above are in the detail namespace, so I am not sure if they are meant to be used by other libraries. Is this a safe operation? Thanks, Ron Side Notes: In my searches, I found a few buggy bits in the docs and code comments: - In boost/iterator/detail/facade_iterator_category.hpp, line 76, there's a comment: // If writability has been disabled per the above metafunction, the // result will not be convertible to output_iterator_tag. This comment corresponds to behavior that was removed in changeset: https://svn.boost.org/trac/boost/changeset/21683 Now the result will never be convertible to output_iterator_tag. - In the documentation for iterator_facade, there's a bit of a booboo where the function is first written: iterator-category(CategoryOrTraversal, value_type, reference) Then defined as: iterator-category(C,R,V) So I think the argument order is flipped.