Hi @, does anybody know why the ostream_iterator class has been mad a template if a template just for the assignment operator would have been sufficient? I.e., why does it say: template<class T> ostream_iterator { ... public: ostream_iterator& operator=(T const&); ... }; instead of ostream_iterator { ... public: template<class T> ostream_iterator& operator=(T const&); ... }; or possibly: template<class os=std::ostream> ostream_iterator { ... public: typedef typename os::char_type char_type; typedef typename os::traits_type traits_type; typedef os ostream_type; template<class T> ostream_iterator& operator=(T const&); ... }; In my compiler version (g++ 3.0 and g++ 3.4) the type T is used nowhere else. As a consequence I have to specify myContainer v; copy(v.begin(), v.end(), ostream_iterator<myContainer::value_type>(cout, "\n")); while it just could be: copy(v.begin(), v.end(), ostream_iterator(cout, "\n")); or copy(v.begin(), v.end(), ostream_iterator<>(cout, "\n")); The answer is obvious for istream_iterators: They provide their input values through the operator*() and have, giving the fact that it does not take any argument, no way to deduce the required return type, so it needs to be specified explicitly. That's different for ostream_iterators. They get their output values as arguments and are perfectly capable of deducing their type, so requiring it as an explicit template argument seems to be an unnecessary over-specification. One could argue, that the template argument adds to type safety, but that sound rather weak to me, especially if standard streams are involved. After all, std::cout and std::cerr are both global, so there's nothing at all to prevent me from printing to them from anywhere else in my application, even from a call implicitly made by function used in the expression above; let alone threads or other operating system processes. So, it seems to me, that the template argument does not provide any additional value but only makes the expression above unnecessary complicate. Am I missing something? Thanks, Andreas