Hello, I've had much use of a small traits class for identifying types that matches the STL Container concept (roughly) . Two functions is made available, is_container<T> and container_category_of<T>. is_container simply evaluates to true_type or false_type, container_category_of tries to categorize T with the following tags. struct non_container_tag {}; struct container_tag {}; struct sequence_container_tag : public container_tag {}; struct associative_container_tag : public container_tag {}; struct hashed_container_tag : public associative_container_tag {}; template<class T, class Tag = container_tag> struct is_container It seems to work for STL containers, boost multi index, boost array etc.. haven't tried with ptr_containers yet but they should work, since the implementation just looks for a couple of member types using BOOST_MPL_HAS_XXX_TRAIT_DEF. Writing stream operators for a container can be implemented like template<class CharType, class CharTrait, class Container> inline typename boost::enable_if<is_container<Container>, basic_ostream<CharType, CharTrait>&>::type operator <<(basic_ostream<CharType, CharTrait>& os, const Container& c) { if (!os.good() ) return os; detail::write_container(os, c, d); return os; } Writing a generic insert() could look something like namespace detail { template<class Container, class T> bool insert(Container& c, const T& t, sequence_container_tag) { c.push_back(t); return true; } template<class Container, class T> bool insert(Container& c, const T& t, associative_container_tag) { return c.insert(t).second; } } template<class Container, class T> bool insert(Container& c, const T& t) { return detail::insert(c, t, container_category_of<Container>::type()); } Could this be of any use in boost? / Christian