boost::mpl submission? [was: function/bind ideas]

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-01-30 09:07:50

At 04:40 PM 1/29/2002, Aleksey Gurtovoy wrote:

 >David Abrahams wrote:
 >> I recently discovered that nontype template parameters other
 >> than integers are much better supported across compilers
 >> than I had previously expected, so now I'm on the lookout
 >> for uses.
 >
 >And there are plenty of them - pointers to (member) functions as non-type
 >template parameters are indeed unexpectedly cool and useful :). For
 >example,
 >here is a simple application of a compile-time state machine generator
 >we've
 >wrote recently:
 >
 >    class player
 >        : state_machine<player>
 >    {
 >    private:
 >        typedef player self_t;
 >
 >        // state invariants
 >        void stopped_state_invariant();
 >        void playing_state_invariant();
 >        void paused_state_invariant();
 >
 >        // states
 >        typedef state<0, &self_t::stopped_state_invariant> stopped;
 >        typedef state<1, &self_t::playing_state_invariant> playing;
 >        typedef state<2, &self_t::paused_state_invariant> paused;
 >
 >    private:
 >        // events
 >        struct start_event;
 >        struct stop_event;
 >        struct pause_event;
 >        struct resume_event;
 >
 >        // transition functions
 >        bool do_start(start_event const&);
 >        bool do_stop(stop_event const&);
 >        bool do_pause(pause_event const&);
 >        bool do_resume(resume_event const&);
 >
 >        // transitions, in the following format:
 >        // | current state | event | next state | transition function |
 >        friend class state_machine<player>;
 >        typedef boost::mpl::list<
                  ^^^^^^^^^^^^^^^^

So when can we expect a submission for formal review?

--Beman

 >              transition<stopped, start_event,  playing, 
&self_t::do_start>
 >            , transition<playing, stop_event,   stopped, 
&self_t::do_stop>
 >            , transition<playing, 
pause_event,  paused,  &self_t::do_pause>
 >            , transition<paused,  resume_event, paused,
 >&self_t::do_resume>
 >            >::type transition_table;
 >    };
 >
 >    // event definitions
 >    struct player::start_event
 >        : player::event
 >    {
 >    };
 >
 >    // ...
 >
 >    int main()
 >    {
 >        player.process_event(player::start_event());
 >        return 0;
 >    }
 >
 >IMO, a programming language that allows you to do something like this is
 >cool by definition :).