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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> |
