Why boost::function_output_iterator has no accessor to the wrapped function/functor? In STL, algorithms using an output iterator or a function/functor usually return the iterator or function/functor received in parameter (e.g. std::copy, std::for_each) because they are passed by copy. Then if I use a boost::function_output_iterator, I can get a copy of that iterator in return, but then there is no way to extract the function/functor. Example: I have a set of points stored in a structure for range query (e.g. a kd-tree). There is a member function to get all points falling inside a given area and it produces its output in an output iterator. Now, suppose I only want to do some computation on those points for which I would actually don't need to store them all, e.g. an average of some kind. I could do the computation on the fly using a boost::function_output_iterator with a functor that accumulates the sum and the number of points and at the end, I would do the division. Alas, I can't unless the functor only keeps reference. I can't do it the classical way I could with std::for_each because I can't access the functor with boost::function_output_iterator. So, long story just to try to show that it would be useful, or is there some other considerations I didn't see that makes it a bad idea? -- Francois Duranleau