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- <title>Chapter 1. Founding idea</title><link rel="stylesheet" href="boostbook.css" type="text/css"><meta name="generator" content="DocBook XSL-NS Stylesheets V1.75.2"><link rel="home" href="index.html" title="Meta State Machine (MSM)"><link rel="up" href="pt01.html" title="Part I. User' guide"><link rel="prev" href="pt01.html" title="Part I. User' guide"><link rel="next" href="ch02.html" title="Chapter 2. UML Short Guide"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 1. Founding idea</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="pt01.html">Prev</a> </td><th width="60%" align="center">Part I. User' guide</th><td width="20%" align="right"> <a accesskey="n" href="ch02.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter 1. Founding idea"><div class="titlepage"><div><div><h2 class="title"><a name="d0e99"></a>Chapter 1. Founding idea</h2></div></div></div><p>Let's start with an example taken from the C++ Template Metaprogramming
- book:</p><pre class="programlisting">class player : public state_machine<player>
- {
- // The list of FSM states enum states { Empty, Open, Stopped, Playing, Paused , initial_state = Empty };
- // transition actions
- void start_playback(play const&) { std::cout << "player::start_playback\n"; }
- void open_drawer(open_close const&) { std::cout << "player::open_drawer\n"; }
- // more transition actions
- ...
- typedef player p; // makes transition table cleaner
- struct transition_table : mpl::vector11<
- // Start Event Target Action
- // +---------+------------+-----------+---------------------------+
- row< Stopped , play , Playing , &p::start_playback >,
- row< Stopped , open_close , Open , &::open_drawer >,
- // +---------+------------+-----------+---------------------------+
- row< Open , open_close , Empty , &p::close_drawer >,
- // +---------+------------+-----------+---------------------------+
- row< Empty , open_close , Open , &p::open_drawer >,
- row< Empty , cd_detected, Stopped , &p::store_cd_info >,
- // +---------+------------+-----------+---------------------------+
- row< Playing , stop , Stopped , &p::stop_playback >,
- row< Playing , pause , Paused , &p::pause_playback >,
- row< Playing , open_close , Open , &p::stop_and_open >,
- // +---------+------------+-----------+---------------------------+
- row< Paused , play , Playing , &p::resume_playback >,
- row< Paused , stop , Stopped , &p::stop_playback >,
- row< Paused , open_close , Open , &p::stop_and_open >
- // +---------+------------+-----------+---------------------------+
- > {};
- // Replaces the default no-transition response.
- template <class Event>
- int no_transition(int state, Event const& e)
- {
- std::cout << "no transition from state " << state << " on event " << typeid(e).name() << std::endl;
- return state;
- }
- }; </pre><p>This example is the foundation for the idea driving MSM: a descriptive and
- expressive language based on a transition table with as little syntactic noise as
- possible, all this while offering as many features from the UML 2.0 standard as
- possible. MSM also offers several expressive state machine definition syntaxes with
- different trade-offs.</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pt01.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt01.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part I. User' guide </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 2. UML Short Guide</td></tr></table></div></body></html>
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