Hi, I recently learned the hard way that the visitor parameter, vis, is passed by value to depth_first_visit, but passed by reference to detail::depth_first_visit_impl. I was writing a function that implemented depth_first_search, but starts each of the visits at vertices with indegree == 0. If my depth_first_search replacement calls boost::depth_first_visit, each call to depth_first_visit makes a copy of the output iterator, which doesn't work for an output iterator with any state (such as a pointer). Calling an internal boost function like detail::depth_first_visit_impl doesn't seem like a good plan. How should I solve this? My short-term work around is to use an output iterator that does not have any state, such as a back_inserter. Cheers, Shaun