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<title>Chapter 1. Founding idea</title><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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