boost_1_45_0/libs/mpl/example/fsm/player.cpp

// Copyright Aleksey Gurtovoy 2002-2004
//
// Distributed under the Boost Software License, Version 1.0. 
// (See accompanying file LICENSE_1_0.txt or copy at 
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/mpl for documentation.

// $Id: player.cpp 49268 2008-10-11 06:26:17Z agurtovoy $
// $Date: 2008-10-11 02:26:17 -0400 (Sat, 11 Oct 2008) $
// $Revision: 49268 $

#include "state_machine.hpp"
#include <boost/mpl/list.hpp>

#include <iostream>

namespace mpl = boost::mpl;

class player
    : public fsm::state_machine<player>
{
 public:
    player() {}

    // events
    struct play_event : event<play_event> {};
    struct stop_event : event<stop_event> {};
    struct pause_event : event<pause_event> {};

// MWCW 8.1 is too eager in inforcing access for non-type template parameters
// private:
    typedef player self_t;
    
    // state invariants
    void stopped_state_invariant() const {}
    void playing_state_invariant() const {}
    void paused_state_invariant() const {}

    // states (invariants are passed as non-type template arguments)
    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:

    // transition functions
    bool do_play(play_event const&) { std::cout << "player::do_play\n"; return true; }
    bool do_stop(stop_event const&) { std::cout << "player::do_stop\n"; return true; }
    bool do_pause(pause_event const&) { std::cout << "player::do_pause\n"; return true; }
    bool do_resume(play_event const&) { std::cout << "player::do_resume\n"; return true; }
    
    // transitions, in the following format:
    // | current state | event | next state | transition function |
    friend class fsm::state_machine<player>;
    typedef mpl::list<
          transition<stopped, play_event,  playing, &player::do_play>
        , transition<playing, stop_event,  stopped, &player::do_stop>
        , transition<playing, pause_event, paused,  &player::do_pause>
        , transition<paused,  play_event,  playing, &player::do_resume>
        , transition<paused,  stop_event,  stopped, &player::do_stop>
        >::type transition_table;
        
    typedef stopped initial_state;
};

int main()
{
    player p;
    p.process_event(player::play_event());
    p.process_event(player::pause_event());
    p.process_event(player::play_event());
    p.process_event(player::stop_event());
    return 0;
}