Hi All I was thinking of implementing a futures service following the asio model of callbacks. This would essentially allow integrating use of futures in the event based model of asio. I would imagine a class like: class futures_service { public: futures_service(io_service& msg_queue); /// Register for a callback when the value contained in that /// future is ready. When the future is ready the handler will /// get posted to the message queue in a manner equivalent to /// calling io_service::dispatch. /// /// Handler should be a functor with the signature: /// void (Future_T&); template <class Future_T, class Handler> void wait_for_async(Future_T future, Handler cb); }; The futures_service could be implemented using the same techniques as boost::wait_for_any (thus would require access to private members of the boost::future classes. I have not come across anything like this in the boost libraries (either in asio or threads). Has this been considered and rejected for some reason? Would boost be interested in it if I were to write it? Which library would it go into, thread or asio? Thanks Will PS. I posted this to the asio and threads lists but got no response so I'm trying here