ceph/src/boost/libs/msm/doc/HTML/ch01.html

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   3    <title>Chapter&nbsp;1.&nbsp;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&nbsp;I.&nbsp;User' guide"><link rel="prev" href="pt01.html" title="Part&nbsp;I.&nbsp;User' guide"><link rel="next" href="ch02.html" title="Chapter&nbsp;2.&nbsp;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&nbsp;1.&nbsp;Founding idea</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="pt01.html">Prev</a>&nbsp;</td><th width="60%" align="center">Part&nbsp;I.&nbsp;User' guide</th><td width="20%" align="right">&nbsp;<a accesskey="n" href="ch02.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter&nbsp;1.&nbsp;Founding idea"><div class="titlepage"><div><div><h2 class="title"><a name="d0e99"></a>Chapter&nbsp;1.&nbsp;Founding idea</h2></div></div></div><p>Let's start with an example taken from the C++ Template Metaprogramming
   4                 book:</p><pre class="programlisting">class player : public state_machine&lt;player&gt;
   5 {
   6   // The list of FSM states enum states { Empty, Open, Stopped, Playing, Paused , initial_state = Empty };
   7
   8   // transition actions
   9   void start_playback(play const&amp;) { std::cout &lt;&lt; "player::start_playback\n"; }
  10   void open_drawer(open_close const&amp;) { std::cout &lt;&lt; "player::open_drawer\n"; }
  11   // more transition actions
  12   ...
  13   typedef player p; // makes transition table cleaner
  14   struct transition_table : mpl::vector11&lt;
  15   //    Start     Event        Target      Action
  16   //   +---------+------------+-----------+---------------------------+
  17     row&lt; Stopped , play       ,  Playing  , &amp;p::start_playback        &gt;,
  18     row&lt; Stopped , open_close ,  Open     , &amp;::open_drawer            &gt;,
  19   //   +---------+------------+-----------+---------------------------+
  20     row&lt; Open    , open_close ,  Empty    , &amp;p::close_drawer          &gt;,
  21   //   +---------+------------+-----------+---------------------------+
  22     row&lt; Empty   , open_close ,  Open     , &amp;p::open_drawer           &gt;,
  23     row&lt; Empty   , cd_detected,  Stopped  , &amp;p::store_cd_info         &gt;,
  24   //   +---------+------------+-----------+---------------------------+
  25     row&lt; Playing , stop       ,  Stopped  , &amp;p::stop_playback         &gt;,
  26     row&lt; Playing , pause      ,  Paused   , &amp;p::pause_playback        &gt;,
  27     row&lt; Playing , open_close ,  Open     , &amp;p::stop_and_open         &gt;,
  28   //   +---------+------------+-----------+---------------------------+
  29     row&lt; Paused  , play       ,  Playing  , &amp;p::resume_playback       &gt;,
  30     row&lt; Paused  , stop       ,  Stopped  , &amp;p::stop_playback         &gt;,
  31     row&lt; Paused  , open_close ,  Open     , &amp;p::stop_and_open         &gt;
  32   //   +---------+------------+-----------+---------------------------+
  33   &gt; {};
  34   // Replaces the default no-transition response.
  35   template &lt;class Event&gt;
  36   int no_transition(int state, Event const&amp; e)
  37   {
  38     std::cout &lt;&lt; "no transition from state " &lt;&lt; state &lt;&lt; " on event " &lt;&lt; typeid(e).name() &lt;&lt; std::endl;
  39     return state;
  40   }
  41 };                        </pre><p>This example is the foundation for the idea driving MSM: a descriptive and
  42                 expressive language based on a transition table with as little syntactic noise as
  43                 possible, all this while offering as many features from the UML 2.0 standard as
  44                 possible. MSM also offers several expressive state machine definition syntaxes with
  45                 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>&nbsp;</td><td width="20%" align="center"><a accesskey="u" href="pt01.html">Up</a></td><td width="40%" align="right">&nbsp;<a accesskey="n" href="ch02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Part&nbsp;I.&nbsp;User' guide&nbsp;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&nbsp;Chapter&nbsp;2.&nbsp;UML Short Guide</td></tr></table></div></body></html>