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  <title>The Boost Statechart Library - Reference</title>
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      <td valign="top" width="300">
        <h3><a href="../../../index.htm"><img alt="C++ Boost" src=
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      <td valign="top">
        <h1 align="center">The Boost Statechart Library</h1>

        <h2 align="center">Reference</h2>
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  <hr>

  <h2>Contents</h2>

  <dl class="page-index">
    <dt><a href="#Concepts">Concepts</a></dt>

    <dd><a href="#Scheduler">Scheduler</a></dd>

    <dd><a href="#FifoWorker">FifoWorker</a></dd>

    <dd><a href="#ExceptionTranslator">ExceptionTranslator</a></dd>

    <dd><a href="#StateBase">StateBase</a></dd>

    <dd><a href="#SimpleState">SimpleState</a></dd>

    <dd><a href="#State">State</a></dd>

    <dd><a href="#Event">Event</a></dd>

    <dt><a href="#state_machine.hpp">state_machine.hpp</a></dt>

    <dd><a href="#ClassTemplatestate_machine">Class template
    <code>state_machine</code></a></dd>

    <dt><a href=
    "#asynchronous_state_machine.hpp">asynchronous_state_machine.hpp</a></dt>

    <dd><a href="#ClassTemplateasynchronous_state_machine">Class template
    <code>asynchronous_state_machine</code></a></dd>

    <dt><a href="#event_processor.hpp">event_processor.hpp</a></dt>

    <dd><a href="#ClassTemplateevent_processor">Class template
    <code>event_processor</code></a></dd>

    <dt><a href="#fifo_scheduler.hpp">fifo_scheduler.hpp</a></dt>

    <dd><a href="#ClassTemplatefifo_scheduler">Class template
    <code>fifo_scheduler</code></a></dd>

    <dt><a href="#exception_translator.hpp">exception_translator.hpp</a></dt>

    <dd><a href="#ClassTemplateexception_translator">Class template
    <code>exception_translator</code></a></dd>

    <dt><a href=
    "#null_exception_translator.hpp">null_exception_translator.hpp</a></dt>

    <dd><a href="#Classnull_exception_translator">Class
    <code>null_exception_translator</code></a></dd>

    <dt>&nbsp;</dt>

    <dt><a href="#simple_state.hpp">simple_state.hpp</a></dt>

    <dd><a href="#Enumhistory_mode">Enum <code>history_mode</code></a></dd>

    <dd><a href="#ClassTemplatesimple_state">Class template
    <code>simple_state</code></a></dd>

    <dt><a href="#state.hpp">state.hpp</a></dt>

    <dd><a href="#ClassTemplatestate">Class template
    <code>state</code></a></dd>

    <dt><a href="#shallow_history.hpp">shallow_history.hpp</a></dt>

    <dd><a href="#ClassTemplateshallow_history">Class template
    <code>shallow_history</code></a></dd>

    <dt><a href="#deep_history.hpp">deep_history.hpp</a></dt>

    <dd><a href="#ClassTemplatedeep_history">Class template
    <code>deep_history</code></a></dd>

    <dt>&nbsp;</dt>

    <dt><a href="#event_base.hpp">event_base.hpp</a></dt>

    <dd><a href="#Classevent_base">Class <code>event_base</code></a></dd>

    <dt><a href="#event.hpp">event.hpp</a></dt>

    <dd><a href="#ClassTemplateevent">Class template
    <code>event</code></a></dd>

    <dt>&nbsp;</dt>

    <dt><a href="#transition.hpp">transition.hpp</a></dt>

    <dd><a href="#ClassTemplatetransition">Class template
    <code>transition</code></a></dd>

    <dt><a href="#in_state_reaction.hpp">in_state_reaction.hpp</a></dt>

    <dd><a href="#ClassTemplatein_state_reaction">Class template
    in_state_reaction</a></dd>

    <dt><a href="#termination.hpp">termination.hpp</a></dt>

    <dd><a href="#ClassTemplatetermination">Class template
    <code>termination</code></a></dd>

    <dt><a href="#deferral.hpp">deferral.hpp</a></dt>

    <dd><a href="#ClassTemplatedeferral">Class template
    <code>deferral</code></a></dd>

    <dt><a href="#custom_reaction.hpp">custom_reaction.hpp</a></dt>

    <dd><a href="#ClassTemplatecustom_reaction">Class template
    <code>custom_reaction</code></a></dd>

    <dt><a href="#result.hpp">result.hpp</a></dt>

    <dd><a href="#Classresult">Class <code>result</code></a></dd>
  </dl>
  <hr>

  <h1><a name="Concepts" id="Concepts">Concepts</a></h1>

  <h2><a name="Scheduler" id="Scheduler">Scheduler</a> concept</h2>

  <p>A Scheduler type defines the following:</p>

  <ul>
    <li>What is passed to the constructors of <code><a href=
    "#ClassTemplateevent_processor">event_processor&lt;&gt;</a></code>
    subtypes and how the lifetime of such objects is managed</li>

    <li>Whether or not multiple <code>event_processor&lt;&gt;</code> subtype
    objects can share the same queue and scheduler thread</li>

    <li>How events are added to the schedulers' queue</li>

    <li>Whether and how to wait for new events when the schedulers' queue
    runs empty</li>

    <li>Whether and what type of locking is used to ensure thread-safety</li>

    <li>Whether it is possible to queue events for no longer existing
    <code>event_processor&lt;&gt;</code> subtype objects and what happens
    when such an event is processed</li>

    <li>What happens when one of the serviced
    <code>event_processor&lt;&gt;</code> subtype objects propagates an
    exception</li>
  </ul>

  <p>For a Scheduler type <code>S</code> and an object <code>cpc</code> of
  type <code>const S::processor_context</code> the following expressions must
  be well-formed and have the indicated results:</p>

  <table border="3" cellpadding="2" width="100%" summary="Scheduler concept">
    <tr>
      <td><b>Expression</b></td>

      <td><b>Type</b></td>

      <td><b>Result</b></td>
    </tr>

    <tr>
      <td><code>cpc.my_scheduler()</code></td>

      <td><code>S &amp;</code></td>

      <td>A reference to the scheduler</td>
    </tr>

    <tr>
      <td><code>cpc.my_handle()</code></td>

      <td><code>S::processor_handle</code></td>

      <td>The handle identifying the
      <code>event_processor&lt;&gt;</code> subtype object</td>
    </tr>
  </table>

  <p>To protect against abuse, all members of
  <code>S::processor_context</code> should be declared private. As a result,
  <code>event_processor&lt;&gt;</code> must be a friend of
  <code>S::processor_context</code>.</p>

  <h2><a name="FifoWorker" id="FifoWorker">FifoWorker</a> concept</h2>

  <p>A FifoWorker type defines the following:</p>

  <ul>
    <li>Whether and how to wait for new work items when the internal work
    queue runs empty</li>

    <li>Whether and what type of locking is used to ensure thread-safety</li>
  </ul>

  <p>For a FifoWorker type <code>F</code>, an object <code>f</code> of that
  type, a <code>const</code> object <code>cf</code> of that type, a
  parameterless function object <code>w</code> of arbitrary type and an
  <code>unsigned long</code> value <code>n</code> the following
  expressions/statements must be well-formed and have the indicated
  results:</p>

  <table border="3" cellpadding="2" width="100%" summary=
  "FifoWorker concept">
    <tr>
      <td><b>Expression/Statement</b></td>

      <td><b>Type</b></td>

      <td><b>Effects/Result</b></td>
    </tr>

    <tr>
      <td><code>F::work_item</code></td>

      <td><code>boost::function0&lt; void &gt;</code></td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>F()</code> or <code>F( false )</code></td>

      <td><code>F</code></td>

      <td>Constructs a <b>non-blocking</b> (see below) object of
      the FifoWorker type. In single-threaded builds the second expression is
      not well-formed</td>
    </tr>

    <tr>
      <td><code>F( true )</code></td>

      <td><code>F</code></td>

      <td>Constructs a <b>blocking</b> (see below) object of the
      FifoWorker type. Not well-formed in single-threaded builds</td>
    </tr>

    <tr>
      <td><code>f.queue_work_item( w );</code></td>

      <td>&nbsp;</td>

      <td>Constructs and queues an object of type
      <code>F::work_item</code>, passing <code>w</code> as the only
      argument</td>
    </tr>

    <tr>
      <td><code>f.terminate();</code></td>

      <td>&nbsp;</td>

      <td>Creates and queues an object of type
      <code>F::work_item</code> that, when later executed in
      <code>operator()()</code>, leads to a modification of internal state so
      that <code>terminated()</code> henceforth returns
      <code>true</code></td>
    </tr>

    <tr>
      <td><code>cf.terminated();</code></td>

      <td><code>bool</code></td>

      <td><code>true</code> if <code>terminate()</code> has been
      called and the resulting work item has been executed in
      <code>operator()()</code>. Returns <code>false</code> otherwise<br>
      <br>
      <b>Must only be called from the thread that also calls
      <code>operator()()</code></b></td>
    </tr>

    <tr>
      <td><code>f( n );</code></td>

      <td><code>unsigned long</code></td>

      <td>
        Enters a loop that, with each cycle, dequeues and calls
        <code>operator()()</code> on the oldest work item in the queue.

        <p>The loop is left and the number of executed work items returned if
        one or more of the following conditions are met:</p>

        <ul>
          <li><code>f.terminated() == true</code></li>

          <li>The application is single-threaded and the internal queue is
          empty</li>

          <li>The application is multi-threaded and the internal queue is
          empty and the worker was created as non-blocking</li>

          <li><code>n != 0</code> and the number of work items that have been
          processed since <code>operator()()</code> was called equals
          <code>n</code></li>
        </ul>

        <p>If the queue is empty and none of the above conditions are met
        then the thread calling <code>operator()()</code> is put into a wait
        state until <code>f.queue_work_item()</code> is called from another
        thread.<br>
        <br>
        <b>Must only be called from exactly one thread</b></p>
      </td>
    </tr>

    <tr>
      <td><code>f();</code></td>

      <td><code>unsigned long</code></td>

      <td>Has exactly the same semantics as <code>f( n );</code>
      with <code>n == 0</code> (see above)</td>
    </tr>
  </table>

  <h2><a name="ExceptionTranslator" id=
  "ExceptionTranslator">ExceptionTranslator</a> concept</h2>

  <p>An ExceptionTranslator type defines how C++ exceptions occurring during
  state machine operation are translated to exception events.</p>

  <p>For an ExceptionTranslator object <code>et</code>, a parameterless
  function object <code>a</code> of arbitrary type returning <code><a href=
  "#Classresult">result</a></code> and a function object <code>eh</code> of
  arbitrary type taking a <code>const <a href=
  "#Classevent_base">event_base</a> &amp;</code> parameter and returning
  <code><a href="#Classresult">result</a></code> the following expression
  must be well-formed and have the indicated results:</p>

  <table border="3" cellpadding="2" width="100%" summary=
  "ExceptionTranslator concept">
    <tr>
      <td><b>Expression</b></td>

      <td><b>Type</b></td>

      <td><b>Effects/Result</b></td>
    </tr>

    <tr>
      <td><code>et(&nbsp;a,&nbsp;eh&nbsp;);</code></td>

      <td><code>result</code></td>

      <td>
        <ol>
          <li>Attempts to execute <code>return a();</code></li>

          <li>If <code>a()</code> propagates an exception, the exception is
          caught</li>

          <li>Inside the catch block calls <code>eh</code>, passing a
          suitable stack-allocated model of the <a href="#Event">Event</a>
          concept</li>

          <li>Returns the result returned by <code>eh</code></li>
        </ol>
      </td>
    </tr>
  </table>

  <h2><a name="StateBase" id="StateBase">StateBase</a> concept</h2>

  <p>A StateBase type is the common base of all states of a given state
  machine type. <code>state_machine&lt;&gt;::state_base_type</code> is a
  model of the StateBase concept.</p>

  <p>For a StateBase type <code>S</code> and a <code>const</code> object
  <code>cs</code> of that type the following expressions must be well-formed
  and have the indicated results:</p>

  <table border="3" cellpadding="2" width="100%" summary="StateBase concept">
    <tr>
      <td><b>Expression</b></td>

      <td><b>Type</b></td>

      <td><b>Result</b></td>
    </tr>

    <tr>
      <td><code>cs.outer_state_ptr()</code></td>

      <td><code>const S *</code></td>

      <td><code>0</code> if <code>cs</code> is an <a href=
      "definitions.html#OutermostState">outermost state</a>, a pointer to the
      direct outer state of <code>cs</code> otherwise</td>
    </tr>

    <tr>
      <td><code>cs.dynamic_type()</code></td>

      <td><code>S::id_type</code></td>

      <td>A value unambiguously identifying the most-derived type
      of <code>cs</code>. <code>S::id_type</code> values are comparable with
      <code>operator==()</code> and <code>operator!=()</code>. An unspecified
      collating order can be established with <code>std::less&lt; S::id_type
      &gt;</code>. In contrast to <code>typeid( cs )</code>, this function is
      available even on platforms that do not support C++ RTTI (or have been
      configured to not support it)</td>
    </tr>

    <tr>
      <td><code>cs.custom_dynamic_type_ptr&lt;<br>
      &nbsp; Type &gt;()</code></td>

      <td><code>const Type *</code></td>

      <td>A pointer to the custom type identifier or
      <code>0</code>. If <code>!= 0</code>, <code>Type</code> must match the
      type of the previously set pointer. This function is only available if
      <a href=
      "configuration.html#ApplicationDefinedMacros">BOOST_STATECHART_USE_NATIVE_RTTI</a>
      is not defined</td>
    </tr>
  </table>

  <h2><a name="SimpleState" id="SimpleState">SimpleState</a> concept</h2>

  <p>A SimpleState type defines one state of a particular state machine.</p>

  <p>For a SimpleState type <code>S</code> and a pointer <code>pS</code>
  pointing to an object of type <code>S</code> allocated with
  <code>new</code> the following expressions/statements must be well-formed
  and have the indicated effects/results:</p>

  <table border="3" cellpadding="2" width="100%" summary=
  "SimpleState concept">
    <tr>
      <td><b>Expression/Statement</b></td>

      <td><b>Type</b></td>

      <td><b>Effects/Result/Notes</b></td>
    </tr>

    <tr>
      <td><code><a href=
      "#ClassTemplatesimple_state">simple_state</a>&lt;<br>
      &nbsp;&nbsp;S,&nbsp;C,&nbsp;I,&nbsp;h&nbsp;&gt;&nbsp;*&nbsp;pB&nbsp;=<br>
      &nbsp;&nbsp;&nbsp;&nbsp;pS;</code></td>

      <td>&nbsp;</td>

      <td><code>simple_state&lt; S, C, I, h &gt;</code> must be
      an unambiguous public base of <code>S</code>. See <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code>
      documentation for the requirements and semantics of <code>C</code>,
      <code>I</code> and <code>h</code></td>
    </tr>

    <tr>
      <td><code>new S()</code></td>

      <td><code>S *</code></td>

      <td>Enters the state <code>S</code>. Certain functions must
      not be called from <code>S::S()</code>, see <a href=
      "#ClassTemplatesimple_state"><code>simple_state&lt;&gt;</code></a>
      documentation for more information</td>
    </tr>

    <tr>
      <td><code>pS-&gt;exit();</code></td>

      <td>&nbsp;</td>

      <td>Exits the state <code>S</code> (first stage). The
      definition of an <code>exit</code> member function within models of the
      SimpleState concept is optional since <code>simple_state&lt;&gt;</code>
      already defines the following public member: <code>void exit()
      {}</code>. <code>exit()</code> is not called when a state is exited
      while an exception is pending, see <code><a href=
      "#simple_state::terminate">simple_state&lt;&gt;::terminate()</a></code>
      for more information</td>
    </tr>

    <tr>
      <td><code>delete pS;</code></td>

      <td>&nbsp;</td>

      <td>Exits the state <code>S</code> (second stage)</td>
    </tr>

    <tr>
      <td><code>S::reactions</code></td>

      <td>An <code>mpl::list&lt;&gt;</code> that is either empty
      or contains instantiations of the <code><a href=
      "#ClassTemplatecustom_reaction">custom_reaction</a></code>,
      <code><a href=
      "#ClassTemplatein_state_reaction">in_state_reaction</a></code>,
      <code><a href="#ClassTemplatedeferral">deferral</a></code>,
      <code><a href="#ClassTemplatetermination">termination</a></code> or
      <code><a href="#ClassTemplatetransition">transition</a></code> class
      templates. If there is only a single reaction then it can also be
      <code>typedef</code>ed directly, without wrapping it into an
      <code>mpl::list&lt;&gt;</code></td>

      <td>The declaration of a <code>reactions</code> member
      <code>typedef</code> within models of the SimpleState concept is
      optional since <code>simple_state&lt;&gt;</code> already defines the
      following public member: <code>typedef mpl::list&lt;&gt;
      reactions;</code></td>
    </tr>
  </table>

  <h2><a name="State" id="State">State</a> concept</h2>

  <p>A State is a <b>refinement</b> of <a href="#SimpleState">SimpleState</a>
  (that is, except for the default constructor a State type must also satisfy
  SimpleState requirements). For a State type <code>S</code>, a pointer
  <code>pS</code> of type <code>S *</code> pointing to an object of type
  <code>S</code> allocated with <code>new</code>, and an object
  <code>mc</code> of type <code>state&lt; S, C, I, h
  &gt;</code><code>::my_context</code> the following expressions/statements
  must be well-formed:</p>

  <table border="3" cellpadding="2" width="100%" summary="State concept">
    <tr>
      <td><b>Expression/Statement</b></td>

      <td><b>Type</b></td>

      <td><b>Effects/Result/Notes</b></td>
    </tr>

    <tr>
      <td><code><a href="#ClassTemplatestate">state</a>&lt;&nbsp;S,&nbsp;C,&nbsp;I,&nbsp;h&nbsp;&gt;&nbsp;*<br>
      &nbsp;&nbsp;pB = pS;</code></td>

      <td>&nbsp;</td>

      <td><code>state&lt; S, C, I, h &gt;</code> must be an
      unambiguous public base of <code>S</code>. See <code><a href=
      "#ClassTemplatestate">state&lt;&gt;</a></code> documentation for the
      requirements and semantics of <code>C</code>, <code>I</code> and
      <code>h</code></td>
    </tr>

    <tr>
      <td><code>new S( mc )</code></td>

      <td><code>S *</code></td>

      <td>Enters the state <code>S</code>. No restrictions exist
      regarding the functions that can be called from <code>S::S()</code> (in
      contrast to the constructors of models of the SimpleState concept).
      <code>mc</code> must be forwarded to <code>state&lt; S, C, I, h
      &gt;::state()</code></td>
    </tr>
  </table>

  <h2><a name="Event" id="Event">Event</a> concept</h2>

  <p>A Event type defines an event for which state machines can define
  reactions.</p>

  <p>For a Event type <code>E</code> and a pointer <code>pCE</code> of type
  <code>const E *</code> pointing to an object of type <code>E</code>
  allocated with <code>new</code> the following expressions/statements must
  be well-formed and have the indicated effects/results:</p>

  <table border="3" cellpadding="2" width="100%" summary="Event concept">
    <tr>
      <td><b>Expression/Statement</b></td>

      <td><b>Type</b></td>

      <td><b>Effects/Result/Notes</b></td>
    </tr>

    <tr>
      <td><code>const <a href="#ClassTemplateevent">event</a>&lt;
      E &gt; * pCB = pCE;</code></td>

      <td>&nbsp;</td>

      <td><code>event&lt; E &gt;</code> must be an unambiguous
      public base of <code>E</code></td>
    </tr>

    <tr>
      <td><code>new E( *pCE )</code></td>

      <td><code>E *</code></td>

      <td>Makes a copy of <code>pE</code></td>
    </tr>
  </table>

  <h1>Header &lt;boost/statechart/<a name="state_machine.hpp" id=
  "state_machine.hpp">state_machine.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatestate_machine" id=
  "ClassTemplatestate_machine">Class template
  <code>state_machine</code></a></h2>

  <p>This is the base class template of all synchronous state machines.</p>

  <h3>Class template <code>state_machine</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "state_machine parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>MostDerived</code></td>

      <td>The most-derived subtype of this class template</td>

      <td>&nbsp;</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>InitialState</code></td>

      <td>A model of the <a href="#SimpleState">SimpleState</a>
      or <a href="#State">State</a> concepts. The <code>Context</code>
      argument passed to the <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base
      of&nbsp; <code>InitialState</code> must be <code>MostDerived</code>.
      That is, <code>InitialState</code> must be an <a href=
      "definitions.html#OutermostState">outermost state</a> of this state
      machine</td>

      <td>The state that is entered when
      <code>state_machine&lt;&gt;<br>
      ::initiate()</code> is called</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>Allocator</code></td>

      <td>A model of the standard Allocator concept</td>

      <td><code>Allocator::rebind&lt;&gt;::other</code> is used
      to allocate and deallocate all <code>simple_state</code> subtype
      objects and internal objects of dynamic storage duration</td>

      <td><code>std::allocator&lt; void &gt;</code></td>
    </tr>

    <tr>
      <td><code>ExceptionTranslator</code></td>

      <td>A model of the ExceptionTranslator concept</td>

      <td>see <a href=
      "#ExceptionTranslator">ExceptionTranslator</a> concept</td>

      <td><code>null_exception_translator</code></td>
    </tr>
  </table>

  <h3>Class template <code>state_machine</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class MostDerived,
    class InitialState,
    class Allocator = std::allocator&lt; void &gt;,
    class ExceptionTranslator = null_exception_translator &gt;
  class state_machine : noncopyable
  {
    public:
      typedef MostDerived outermost_context_type;

      void <a href="#initiate">initiate</a>();
      void <a href="#terminate">terminate</a>();
      bool <a href="#terminated">terminated</a>() const;

      void <a href="#process_event">process_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; );

      template&lt; class Target &gt;
      Target <a href="#state_cast">state_cast</a>() const;
      template&lt; class Target &gt;
      Target <a href="#state_downcast">state_downcast</a>() const;

      // a model of the <a href="#StateBase">StateBase</a> concept
      typedef <i>implementation-defined</i> state_base_type;
      // a model of the standard Forward Iterator concept
      typedef <i>implementation-defined</i> state_iterator;

      state_iterator <a href="#state_begin">state_begin</a>() const;
      state_iterator <a href="#state_end">state_end</a>() const;

      void <a href="#unconsumed_event">unconsumed_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; ) {}

    protected:
      <a href="#state_machine">state_machine</a>();
      <a href="#state_machinedtor">~state_machine</a>();

      void <a href="#post_event2">post_event</a>(
        const intrusive_ptr&lt; const <a href=
"#Classevent_base">event_base</a> &gt; &amp; );
      void <a href="#post_event3">post_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; );

      const event_base * <a href="#triggering_event1">triggering_event</a>() const;
  };
}
}
</pre>

  <h3>Class template <code>state_machine</code> constructor and
  destructor</h3>
  <pre>
<a name="state_machine" id="state_machine">state_machine</a>();
</pre>

  <p><b>Effects</b>: Constructs a non-running state machine</p>
  <pre>
<a name="state_machinedtor" id="state_machinedtor">~state_machine</a>();
</pre>

  <p><b>Effects</b>: Destructs the currently active outermost state and all
  its direct and indirect inner states. Innermost states are destructed
  first. Other states are destructed as soon as all their direct and indirect
  inner states have been destructed. The inner states of each state are
  destructed according to the number of their orthogonal region. The state in
  the orthogonal region with the highest number is always destructed first,
  then the state in the region with the second-highest number and so on<br>
  <b>Note</b>: Does not attempt to call any <code>exit</code> member
  functions</p>

  <h3>Class template <code>state_machine</code> modifier functions</h3>
  <pre>
void <a name="initiate" id="initiate">initiate</a>();
</pre>

  <p><b>Effects</b>:</p>

  <ol>
    <li>Calls <code>terminate()</code></li>

    <li>Constructs a function object <code>action</code> with a
    parameter-less <code>operator()()</code> returning <code><a href=
    "#Classresult">result</a></code> that

      <ol type="a">
        <li>enters (constructs) the state specified with the
        <code>InitialState</code> template parameter</li>

        <li>enters the tree formed by the direct and indirect inner initial
        states of <code>InitialState</code> depth first. The inner states of
        each state are entered according to the number of their orthogonal
        region. The state in orthogonal region 0 is always entered first,
        then the state in region 1 and so on</li>
      </ol>
    </li>

    <li>Constructs a function object <code>exceptionEventHandler</code> with
    an <code>operator()()</code> returning <code>result</code> and accepting
    an exception event parameter that processes the passed exception event,
    with the following differences to the processing of normal events:

      <ul type="disc">
        <li>From the moment when the exception has been thrown until right
        after the execution of the exception event reaction, states that need
        to be exited are only destructed but no <code>exit</code> member
        functions are called</li>

        <li><a href="definitions.html#Reaction">Reaction</a> search always
        starts with the outermost <a href=
        "definitions.html#UnstableState">unstable state</a></li>

        <li>As for normal events, reaction search moves outward when the
        current state cannot handle the event. However, if there is no outer
        state (an <a href="definitions.html#OutermostState">outermost
        state</a> has been reached) the reaction search is considered
        unsuccessful. That is, exception events will never be dispatched to
        orthogonal regions other than the one that caused the exception
        event</li>

        <li>Should an exception be thrown during exception event reaction
        search or reaction execution then the exception is propagated out of
        the <code>exceptionEventHandler</code> function object (that is,
        <code>ExceptionTranslator</code> is <b>not</b> used to translate
        exceptions thrown while processing an exception event)</li>

        <li>If no reaction could be found for the exception event or if the
        state machine is not stable after processing the exception event, the
        original exception is rethrown. Otherwise, a <code><a href=
        "#Classresult">result</a></code> object is returned equal to the one
        returned by <code>simple_state&lt;&gt;::discard_event()</code></li>
      </ul>
    </li>

    <li>Passes <code>action</code> and <code>exceptionEventHandler</code> to
    <code>ExceptionTranslator::operator()()</code>. If
    <code>ExceptionTranslator::operator()()</code> throws an exception, the
    exception is propagated to the caller. If the caller catches the
    exception, the currently active outermost state and all its direct and
    indirect inner states are destructed. Innermost states are destructed
    first. Other states are destructed as soon as all their direct and
    indirect inner states have been destructed. The inner states of each
    state are destructed according to the number of their orthogonal region.
    The state in the orthogonal region with the highest number is always
    destructed first, then the state in the region with the second-highest
    number and so on. Continues with step 5 otherwise (the return value is
    discarded)</li>

    <li>Processes all posted events (see <code>process_event()</code>).
    Returns to the caller if there are no more posted events</li>
  </ol>

  <p><b>Throws</b>: Any exceptions propagated from
  <code>ExceptionTranslator::operator()()</code>. Exceptions never originate
  in the library itself but only in code supplied through template
  parameters:</p>

  <ul>
    <li><code>Allocator::rebind&lt;&gt;::other::allocate()</code></li>

    <li>state constructors</li>

    <li><code>react</code> member functions</li>

    <li><code>exit</code> member functions</li>

    <li>transition-actions</li>
  </ul>
  <pre>
void <a name="terminate" id="terminate">terminate</a>();
</pre>

  <p><b>Effects</b>:</p>

  <ol>
    <li>Constructs a function object <code>action</code> with a
    parameter-less <code>operator()()</code> returning <code><a href=
    "#Classresult">result</a></code> that <a href=
    "#simple_state::terminate">terminates</a> the currently active outermost
    state, discards all remaining events and clears all history
    information</li>

    <li>Constructs a function object <code>exceptionEventHandler</code> with
    an <code>operator()()</code> returning <code><a href=
    "#Classresult">result</a></code> and accepting an exception event
    parameter that processes the passed exception event, with the following
    differences to the processing of normal events:

      <ul type="disc">
        <li>From the moment when the exception has been thrown until right
        after the execution of the exception event reaction, states that need
        to be exited are only destructed but no <code>exit</code> member
        functions are called</li>

        <li><a href="definitions.html#Reaction">Reaction</a> search always
        starts with the outermost <a href=
        "definitions.html#UnstableState">unstable state</a></li>

        <li>As for normal events, reaction search moves outward when the
        current state cannot handle the event. However, if there is no outer
        state (an <a href="definitions.html#OutermostState">outermost
        state</a> has been reached) the reaction search is considered
        unsuccessful. That is, exception events will never be dispatched to
        orthogonal regions other than the one that caused the exception
        event</li>

        <li>Should an exception be thrown during exception event reaction
        search or reaction execution then the exception is propagated out of
        the <code>exceptionEventHandler</code> function object (that is,
        <code>ExceptionTranslator</code> is <b>not</b> used to translate
        exceptions thrown while processing an exception event)</li>

        <li>If no reaction could be found for the exception event or if the
        state machine is not stable after processing the exception event, the
        original exception is rethrown. Otherwise, a <code><a href=
        "#Classresult">result</a></code> object is returned equal to the one
        returned by <code>simple_state&lt;&gt;::discard_event()</code></li>
      </ul>
    </li>

    <li>Passes <code>action</code> and <code>exceptionEventHandler</code> to
    <code>ExceptionTranslator::operator()()</code>. If
    <code>ExceptionTranslator::operator()()</code> throws an exception, the
    exception is propagated to the caller. If the caller catches the
    exception, the currently active outermost state and all its direct and
    indirect inner states are destructed. Innermost states are destructed
    first. Other states are destructed as soon as all their direct and
    indirect inner states have been destructed. The inner states of each
    state are destructed according to the number of their orthogonal region.
    The state in the orthogonal region with the highest number is always
    destructed first, then the state in the region with the second-highest
    number and so on. Otherwise, returns to the caller</li>
  </ol>

  <p><b>Throws</b>: Any exceptions propagated from
  <code>ExceptionTranslator::operator()</code>. Exceptions never originate in
  the library itself but only in code supplied through template
  parameters:</p>

  <ul>
    <li><code>Allocator::rebind&lt;&gt;::other::allocate()</code></li>

    <li>state constructors</li>

    <li><code>react</code> member functions</li>

    <li><code>exit</code> member functions</li>

    <li>transition-actions</li>
  </ul>
  <pre>
void <a name="process_event" id=
"process_event">process_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; );
</pre>

  <p><b>Effects</b>:</p>

  <ol>
    <li>Selects the passed event as the current event (henceforth referred to
    as <code>currentEvent</code>)</li>

    <li>Starts a new <a href="definitions.html#Reaction">reaction</a>
    search</li>

    <li>Selects an arbitrary but in this reaction search not yet visited
    state from all the currently active <a href=
    "definitions.html#InnermostState">innermost states</a>. If no such state
    exists then continues with step 10</li>

    <li>Constructs a function object <code>action</code> with a
    parameter-less <code>operator()()</code> returning <code><a href=
    "#Classresult">result</a></code> that does the following:

      <ol type="a">
        <li>Searches a reaction suitable for <code>currentEvent</code>,
        starting with the current innermost state and moving outward until a
        state defining a reaction for the event is found. Returns
        <code>simple_state&lt;&gt;::forward_event()</code> if no reaction has
        been found</li>

        <li>Executes the found reaction. If the reaction result is equal to
        the return value of
        <code>simple_state&lt;&gt;::forward_event()</code> then resumes the
        reaction search (step a). Returns the reaction result otherwise</li>
      </ol>
    </li>

    <li>Constructs a function object <code>exceptionEventHandler</code>
    returning <code><a href="#Classresult">result</a></code> and accepting an
    exception event parameter that processes the passed exception event, with
    the following differences to the processing of normal events:

      <ul type="disc">
        <li>From the moment when the exception has been thrown until right
        after the execution of the exception event reaction, states that need
        to be exited are only destructed but no <code>exit</code> member
        functions are called</li>

        <li>If the state machine is stable when the exception event is
        processed then exception event reaction search starts with the
        innermost state that was last visited during the last normal event
        reaction search (the exception event was generated as a result of
        this normal reaction search)</li>

        <li>If the state machine is <a href=
        "definitions.html#UnstableStateMachine">unstable</a> when the
        exception event is processed then exception event reaction search
        starts with the outermost <a href=
        "definitions.html#UnstableState">unstable state</a></li>

        <li>As for normal events, reaction search moves outward when the
        current state cannot handle the event. However, if there is no outer
        state (an <a href="definitions.html#OutermostState">outermost
        state</a> has been reached) the reaction search is considered
        unsuccessful. That is, exception events will never be dispatched to
        orthogonal regions other than the one that caused the exception
        event</li>

        <li>Should an exception be thrown during exception event reaction
        search or reaction execution then the exception is propagated out of
        the <code>exceptionEventHandler</code> function object (that is,
        <code>ExceptionTranslator</code> is <b>not</b> used to translate
        exceptions thrown while processing an exception event)</li>

        <li>If no reaction could be found for the exception event or if the
        state machine is not stable after processing the exception event, the
        original exception is rethrown. Otherwise, a <code><a href=
        "#Classresult">result</a></code> object is returned equal to the one
        returned by <code>simple_state&lt;&gt;::discard_event()</code></li>
      </ul>
    </li>

    <li>Passes <code>action</code> and <code>exceptionEventHandler</code> to
    <code>ExceptionTranslator::operator()()</code>. If
    <code>ExceptionTranslator::operator()()</code> throws an exception, the
    exception is propagated to the caller. If the caller catches the
    exception, the currently active outermost state and all its direct and
    indirect inner states are destructed. Innermost states are destructed
    first. Other states are destructed as soon as all their direct and
    indirect inner states have been destructed. The inner states of each
    state are destructed according to the number of their orthogonal region.
    The state in the orthogonal region with the highest number is always
    destructed first, then the state in the region with the second-highest
    number and so on. Otherwise continues with step 7</li>

    <li>If the return value of <code>ExceptionTranslator::operator()()</code>
    is equal to the one of <code>simple_state&lt;&gt;::forward_event()</code>
    then continues with step 3</li>

    <li>If the return value of <code>ExceptionTranslator::operator()()</code>
    is equal to the one of <code>simple_state&lt;&gt;::defer_event()</code>
    then the return value of <code>currentEvent.<a href=
    "#intrusive_from_this">intrusive_from_this</a>()</code> is stored in the
    deferred events queue. Continues with step 11</li>

    <li>If the return value of <code>ExceptionTranslator::operator()()</code>
    is equal to the one of <code>simple_state&lt;&gt;::discard_event()</code>
    then continues with step 11</li>

    <li>Calls <code>static_cast&lt; MostDerived * &gt;( this
    )-&gt;unconsumed_event( currentEvent )</code>. If
    <code>unconsumed_event()</code> throws an exception, the exception is
    propagated to the caller. Such an exception never leads to the
    destruction of any states (in contrast to exceptions propagated from
    <code>ExceptionTranslator::operator()()</code>)</li>

    <li>If the posted events queue is non-empty then dequeues the first
    event, selects it as <code>currentEvent</code> and continues with step 2.
    Returns to the caller otherwise</li>
  </ol>

  <p><b>Throws</b>: Any exceptions propagated from
  <code>MostDerived::unconsumed_event()</code> or
  <code>ExceptionTranslator::operator()</code>. Exceptions never originate in
  the library itself but only in code supplied through template
  parameters:</p>

  <ul>
    <li><code>Allocator::rebind&lt;&gt;::other::allocate()</code></li>

    <li>state constructors</li>

    <li><code>react</code> member functions</li>

    <li><code>exit</code> member functions</li>

    <li>transition-actions</li>

    <li><code>MostDerived::unconsumed_event()</code></li>
  </ul>
  <pre>
void <a name="post_event2" id="post_event2">post_event</a>(
  const intrusive_ptr&lt; const <a href=
"#Classevent_base">event_base</a> &gt; &amp; );
</pre>

  <p><b>Effects</b>: Pushes the passed event into the posted events queue<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>Allocator::allocate()</code></p>
  <pre>
void <a name="post_event3" id="post_event3">post_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; evt );
</pre>

  <p><b>Effects</b>: <code>post_event( evt.intrusive_from_this()
  );</code><br>
  <b>Throws</b>: Any exceptions propagated from
  <code>Allocator::allocate()</code></p>
  <pre>
void <a name="unconsumed_event" id=
"unconsumed_event">unconsumed_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; evt );
</pre>

  <p><b>Effects</b>: None<br>
  <b>Note</b>: This function (or, if present, the equally named derived class
  member function) is called by <a href="#process_event">process_event</a>()
  whenever a dispatched event did not trigger a reaction, see <a href=
  "#process_event">process_event</a>() effects, point 10 for more
  information.</p>

  <h3>Class template <code>state_machine</code> observer functions</h3>
  <pre>
bool <a name="terminated" id="terminated">terminated</a>() const;
</pre>

  <p><b>Returns</b>: <code>true</code>, if the machine is terminated. Returns
  <code>false</code> otherwise<br>
  <b>Note</b>: Is equivalent to <code>state_begin() == state_end()</code></p>
  <pre>
template&lt; class Target &gt;
Target <a name="state_cast" id="state_cast">state_cast</a>() const;
</pre>

  <p><b>Returns</b>: Depending on the form of <code>Target</code> either a
  reference or a pointer to <code>const</code> if at least one of the
  currently active states can successfully be <code>dynamic_cast</code> to
  <code>Target</code>. Returns <code>0</code> for pointer targets and throws
  <code>std::bad_cast</code> for reference targets otherwise.
  <code>Target</code> can take either of the following forms: <code>const
  Class *</code> or <code>const Class &amp;</code><br>
  <b>Throws</b>: <code>std::bad_cast</code> if <code>Target</code> is a
  reference type and none of the active states can be
  <code>dynamic_cast</code> to Target<br>
  <b>Note</b>: The search sequence is the same as for <code><a href=
  "#process_event">process_event</a>()</code></p>
  <pre>
template&lt; class Target &gt;
Target <a name="state_downcast" id=
"state_downcast">state_downcast</a>() const;
</pre>

  <p><b>Requires</b>: For reference targets the compiler must support partial
  specialization of class templates, otherwise a compile-time error will
  result. The type denoted by <code>Target</code> must be a model of the
  <a href="#SimpleState">SimpleState</a> or <a href="#State">State</a>
  concepts<br>
  <b>Returns</b>: Depending on the form of <code>Target</code> either a
  reference or a pointer to <code>const</code> if <code>Target</code> is
  equal to the most-derived type of a currently active state. Returns
  <code>0</code> for pointer targets and throws <code>std::bad_cast</code>
  for reference targets otherwise. <code>Target</code> can take either of the
  following forms: <code>const Class *</code> or <code>const Class
  &amp;</code><br>
  <b>Throws</b>: <code>std::bad_cast</code> if <code>Target</code> is a
  reference type and none of the active states has a most derived type equal
  to <code>Target</code><br>
  <b>Note</b>: The search sequence is the same as for <code><a href=
  "#process_event">process_event</a>()</code></p>
  <pre>
state_iterator <a name="state_begin" id=
"state_begin">state_begin</a>() const;
</pre>
  <pre>
state_iterator <a name="state_end" id="state_end">state_end</a>() const;
</pre>

  <p><b>Return</b>: Iterator objects, the range [<code>state_begin()</code>,
  <code>state_end()</code>) refers to all currently active <a href=
  "definitions.html#InnermostState">innermost states</a>. For an object
  <code>i</code> of type <code>state_iterator</code>, <code>*i</code> returns
  a <code>const state_base_type &amp;</code> and
  <code>i.operator-&gt;()</code> returns a <code>const state_base_type
  *</code><br>
  <b>Note</b>: The position of a given innermost state in the range is
  arbitrary. It may change with each call to a modifier function. Moreover,
  all iterators are invalidated whenever a modifier function is called</p>
  <pre>
const event_base * <a name="triggering_event1" id="triggering_event1">triggering_event</a>();
</pre>

  <p><b>Returns</b>: A pointer to the event that triggered the reaction that is currently
  being executed. Returns <code>0</code> if no reaction is being executed or if the current
  reaction was triggered by either <code><a href="#initiate">initiate</a>()</code> or
  <code><a href="#terminate">terminate</a>()</code>
  </p>

  <h1>Header &lt;boost/statechart/<br>
  <a name="asynchronous_state_machine.hpp" id=
  "asynchronous_state_machine.hpp">asynchronous_state_machine.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplateasynchronous_state_machine" id=
  "ClassTemplateasynchronous_state_machine">Class template
  <code>asynchronous_state_machine</code></a></h2>

  <p>This is the base class template of all asynchronous state machines.</p>

  <h3>Class template <code>asynchronous_state_machine</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "asynchronous_state_machine parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>MostDerived</code></td>

      <td>The most-derived subtype of this class template</td>

      <td>&nbsp;</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>InitialState</code></td>

      <td>A model of the <a href="#SimpleState">SimpleState</a>
      or <a href="#State">State</a> concepts. The <code>Context</code>
      argument passed to the <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base of
      <code>InitialState</code> must be <code>MostDerived</code>. That is,
      <code>InitialState</code> must be an <a href=
      "definitions.html#OutermostState">outermost state</a> of this state
      machine</td>

      <td>The state that is entered when the state machine is
      initiated through the <code>Scheduler</code> object</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>Scheduler</code></td>

      <td>A model of the Scheduler concept</td>

      <td>see <a href="#Scheduler">Scheduler</a> concept</td>

      <td><code>fifo_scheduler&lt;&gt;</code></td>
    </tr>

    <tr>
      <td><code>Allocator</code></td>

      <td>A model of the standard Allocator concept</td>

      <td>&nbsp;</td>

      <td><code>std::allocator&lt; void &gt;</code></td>
    </tr>

    <tr>
      <td><code>ExceptionTranslator</code></td>

      <td>A model of the ExceptionTranslator concept</td>

      <td>see <a href=
      "#ExceptionTranslator">ExceptionTranslator</a> concept</td>

      <td><code>null_exception_translator</code></td>
    </tr>
  </table>

  <h3>Class template <code>asynchronous_state_machine</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class MostDerived,
    class InitialState,
    class Scheduler = fifo_scheduler&lt;&gt;,
    class Allocator = std::allocator&lt; void &gt;,
    class ExceptionTranslator = null_exception_translator &gt;
  class asynchronous_state_machine :
    public state_machine&lt;
      MostDerived, InitialState, Allocator, ExceptionTranslator &gt;,
    public event_processor&lt; Scheduler &gt;
  {
    protected:
      typedef asynchronous_state_machine my_base;

      asynchronous_state_machine(
        typename event_processor&lt; Scheduler &gt;::my_context ctx );
      ~asynchronous_state_machine();  
  };
}
}
</pre>

  <h3>Class template <code>asynchronous_state_machine</code> constructor and
  destructor</h3>
  <pre>
asynchronous_state_machine(
  typename event_processor&lt; Scheduler &gt;::my_context ctx );
</pre>

  <p><b>Effects</b>: Constructs a non-running asynchronous state machine<br>
  <b>Note</b>: Users cannot create
  <code>asynchronous_state_machine&lt;&gt;</code> subtype objects directly.
  This can only be done through an object of the <code>Scheduler</code>
  class</p>
  <pre>
~asynchronous_state_machine();
</pre>

  <p><b>Effects</b>: Destructs the state machine<br>
  <b>Note</b>: Users cannot destruct
  <code>asynchronous_state_machine&lt;&gt;</code> subtype objects directly.
  This can only be done through an object of the <code>Scheduler</code>
  class</p>

  <h1>Header &lt;boost/statechart/<a name="event_processor.hpp" id=
  "event_processor.hpp">event_processor.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplateevent_processor" id=
  "ClassTemplateevent_processor">Class template
  <code>event_processor</code></a></h2>

  <p>This is the base class template of all types that process events.
  <code>asynchronous_state_machine&lt;&gt;</code> is just one possible event
  processor implementation.</p>

  <h3>Class template <code>event_processor</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "event_processor parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>
    </tr>

    <tr>
      <td><code>Scheduler</code></td>

      <td>A model of the Scheduler concept</td>

      <td>see <a href="#Scheduler">Scheduler</a> concept</td>
    </tr>
  </table>

  <h3>Class template <code>event_processor</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class Scheduler &gt;
  class event_processor
  {
    public:
      virtual <a href="#event_processordtor">~event_processor</a>();

      Scheduler &amp; <a href="#my_scheduler">my_scheduler</a>() const;

      typedef typename Scheduler::processor_handle
        processor_handle;
      processor_handle <a href="#my_handle">my_handle</a>() const;

      void <a href="#event_processor::initiate">initiate</a>();
      void <a href=
"#event_processor::process_event">process_event</a>( const event_base &amp; evt );
      void <a href="#event_processor::terminate">terminate</a>();

    protected:
      typedef const typename Scheduler::processor_context &amp;
        my_context;
      <a href="#event_processor">event_processor</a>( my_context ctx );

    private:
      virtual void initiate_impl() = 0;
      virtual void process_event_impl(
        const event_base &amp; evt ) = 0;
      virtual void terminate_impl() = 0;
  };
}
}
</pre>

  <h3>Class template <code>event_processor</code> constructor and
  destructor</h3>
  <pre>
<a name="event_processor" id=
"event_processor">event_processor</a>( my_context ctx );
</pre>

  <p><b>Effects</b>: Constructs an event processor object and stores copies
  of the reference returned by <code>myContext.my_scheduler()</code> and the
  object returned by <code>myContext.my_handle()</code><br>
  <b>Note</b>: Users cannot create <code>event_processor&lt;&gt;</code>
  subtype objects directly. This can only be done through an object of the
  <code>Scheduler</code> class</p>
  <pre>
virtual <a name="event_processordtor" id=
"event_processordtor">~event_processor</a>();
</pre>

  <p><b>Effects</b>: Destructs an event processor object<br>
  <b>Note</b>: Users cannot destruct <code>event_processor&lt;&gt;</code>
  subtype objects directly. This can only be done through an object of the
  <code>Scheduler</code> class</p>

  <h3>Class template <code>event_processor</code> modifier functions</h3>
  <pre>
void <a name="event_processor::initiate" id=
"event_processor::initiate">initiate</a>();
</pre>

  <p><b>Effects</b>: <code>initiate_impl();<br></code><b>Throws</b>: Any
  exceptions propagated from the implementation of
  <code>initiate_impl()</code></p>
  <pre>
void <a name="event_processor::process_event" id=
"event_processor::process_event">process_event</a>( const event_base &amp; evt );
</pre>

  <p><b>Effects</b>: <code>process_event_impl( evt
  );<br></code><b>Throws</b>: Any exceptions propagated from the
  implementation of <code>process_event_impl()</code></p>
  <pre>
void <a name="event_processor::terminate" id=
"event_processor::terminate">terminate</a>();
</pre>

  <p><b>Effects</b>: <code>terminate_impl();<br></code><b>Throws</b>: Any
  exceptions propagated from the implementation of
  <code>terminate_impl()</code></p>

  <h3>Class template <code>event_processor</code> observer functions</h3>
  <pre>
Scheduler &amp; <a name="my_scheduler" id=
"my_scheduler">my_scheduler</a>() const;
</pre>

  <p><b>Returns</b>: The <code>Scheduler</code> reference obtained in the
  constructor</p>
  <pre>
processor_handle <a name="my_handle" id="my_handle">my_handle</a>() const;
</pre>

  <p><b>Returns</b>: The <code>processor_handle</code> object obtained in the
  constructor</p>

  <h1>Header &lt;boost/statechart/<a name="fifo_scheduler.hpp" id=
  "fifo_scheduler.hpp">fifo_scheduler.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatefifo_scheduler" id=
  "ClassTemplatefifo_scheduler">Class template
  <code>fifo_scheduler</code></a></h2>

  <p>This class template is a model of the <a href="#Scheduler">Scheduler</a>
  concept.</p>

  <h3>Class template <code>fifo_scheduler</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "fifo_scheduler parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>FifoWorker</code></td>

      <td>A model of the FifoWorker concept</td>

      <td>see <a href="#FifoWorker">FifoWorker</a> concept</td>

      <td><code>fifo_worker&lt;&gt;</code></td>
    </tr>

    <tr>
      <td><code>Allocator</code></td>

      <td>A model of the standard Allocator concept</td>

      <td>&nbsp;</td>

      <td><code>std::allocator&lt;&nbsp;void&nbsp;&gt;</code></td>
    </tr>
  </table>

  <h3>Class template <code>fifo_scheduler</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class FifoWorker = fifo_worker&lt;&gt;,
    class Allocator = std::allocator&lt; void &gt; &gt;
  class fifo_scheduler : noncopyable
  {
    public:
      <a href=
"#fifo_scheduler::fifo_scheduler">fifo_scheduler</a>( bool waitOnEmptyQueue = false );

      typedef <i>implementation-defined</i> processor_handle;

      class processor_context : noncopyable
      {
        processor_context(
          fifo_scheduler &amp; scheduler,
          const processor_handle &amp; theHandle );

        fifo_scheduler &amp; my_scheduler() const;
        const processor_handle &amp; my_handle() const;

        friend class fifo_scheduler;
        friend class event_processor&lt; fifo_scheduler &gt;;
      };

      template&lt; class Processor &gt;
      processor_handle <a href="#create_processor">create_processor</a>();
      template&lt; class Processor, typename Param1 &gt;
      processor_handle <a href=
"#create_processor1">create_processor</a>( Param1 param1 );

      // More create_processor overloads

      void <a href=
"#destroy_processor">destroy_processor</a>( processor_handle processor );

      void <a href=
"#initiate_processor">initiate_processor</a>( processor_handle processor );
      void <a href=
"#terminate_processor">terminate_processor</a>( processor_handle processor );

      typedef intrusive_ptr&lt; const event_base &gt; event_ptr_type;

      void <a href="#queue_event">queue_event</a>(
        const processor_handle &amp; processor,
        const event_ptr_type &amp; pEvent );

      typedef typename FifoWorker::work_item work_item;

      void <a href=
"#queue_work_item">queue_work_item</a>( const work_item &amp; item );

      void <a href="#fifo_scheduler::terminate">terminate</a>();
      bool <a href="#fifo_scheduler::terminated">terminated</a>() const;

      unsigned long <a href="#operatorfuncall">operator()</a>(
        unsigned long maxEventCount = 0 );
  };
}
}
</pre>

  <h3>Class template <code>fifo_scheduler</code> constructor</h3>
  <pre>
<a name="fifo_scheduler::fifo_scheduler" id=
"fifo_scheduler::fifo_scheduler">fifo_scheduler</a>( bool waitOnEmptyQueue = false );
</pre>

  <p><b>Effects</b>: Constructs a <code>fifo_scheduler&lt;&gt;</code> object.
  In multi-threaded builds, <code>waitOnEmptyQueue</code> is forwarded to the
  constructor of a data member of type <code>FifoWorker</code>. In
  single-threaded builds, the <code>FifoWorker</code> data member is
  default-constructed<br>
  <b>Note</b>: In single-threaded builds the
  <code>fifo_scheduler&lt;&gt;</code> constructor does not accept any
  parameters and <code>operator()()</code> thus always returns to the caller
  when the event queue is empty</p>

  <h3>Class template <code>fifo_scheduler</code> modifier functions</h3>
  <pre>
template&lt; class Processor &gt;
processor_handle <a name="create_processor" id=
"create_processor">create_processor</a>();
</pre>

  <p><b>Requires</b>: The <code>Processor</code> type must be a direct or
  indirect subtype of the <a href=
  "#ClassTemplateevent_processor"><code>event_processor</code></a> class
  template<br>
  <b>Effects</b>: Creates and passes to
  <code>FifoWorker::queue_work_item()</code> an object of type
  <code>FifoWorker::work_item</code> that, when later executed in
  <code>FifoWorker::operator()()</code>, leads to a call to the constructor
  of <code>Processor</code>, passing an appropriate
  <code>processor_context</code> object as the only argument<br>
  <b>Returns</b>: A <code>processor_handle</code> object that henceforth
  identifies the created event processor object<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>FifoWorker::work_item()</code> and
  <code>FifoWorker::queue_work_item()</code><br>
  <b>Caution</b>: The current implementation of this function makes an
  (indirect) call to global <code>operator new()</code>. Unless global
  <code>operator new()</code> is replaced, care must be taken when to call
  this function in applications with hard real-time requirements</p>
  <pre>
template&lt; class Processor, typename Param1 &gt;
processor_handle <a name="create_processor1" id=
"create_processor1">create_processor( Param1 param1 )</a>;
</pre>

  <p><b>Requires</b>: The <code>Processor</code> type must be a direct or
  indirect subtype of the <a href=
  "#ClassTemplateevent_processor"><code>event_processor</code></a> class
  template<br>
  <b>Effects</b>: Creates and passes to
  <code>FifoWorker::queue_work_item()</code> an object of type
  <code>FifoWorker::work_item</code> that, when later executed in
  <code>FifoWorker::operator()()</code>, leads to a call to the constructor
  of <code>Processor</code>, passing an appropriate
  <code>processor_context</code> object and <code>param1</code> as
  arguments<br>
  <b>Returns</b>: A <code>processor_handle</code> object that henceforth
  identifies the created event processor object<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>FifoWorker::work_item()</code> and
  <code>FifoWorker::queue_work_item()</code><b><br>
  Note</b>: <code>boost::ref()</code> and <code>boost::cref()</code> can be
  used to pass arguments by reference rather than by copy.
  <code>fifo_scheduler&lt;&gt;</code> has 5 additional
  <code>create_processor&lt;&gt;</code> overloads, allowing to pass up to 6
  custom arguments to the constructors of event processors<br>
  <b>Caution</b>: The current implementation of this and all other overloads
  make (indirect) calls to global <code>operator new()</code>. Unless global
  <code>operator new()</code> is replaced, care must be taken when to call
  these overloads in applications with hard real-time requirements</p>
  <pre>
void <a name="destroy_processor" id=
"destroy_processor">destroy_processor</a>( processor_handle processor );
</pre>

  <p><b>Requires</b>: <code>processor</code> was obtained from a call to one
  of the <code>create_processor&lt;&gt;()</code> overloads on the same
  <code>fifo_scheduler&lt;&gt;</code> object<br>
  <b>Effects</b>: Creates and passes to
  <code>FifoWorker::queue_work_item()</code> an object of type
  <code>FifoWorker::work_item</code> that, when later executed in
  <code>FifoWorker::operator()()</code>, leads to a call to the destructor of
  the event processor object associated with <code>processor</code>. The
  object is silently discarded if the event processor object has been
  destructed before<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>FifoWorker::work_item()</code> and
  <code>FifoWorker::queue_work_item()</code><br>
  <b>Caution</b>: The current implementation of this function leads to an
  (indirect) call to global <code>operator delete()</code> (the call is made
  when the last <code>processor_handle</code> object associated with the
  event processor object is destructed). Unless global <code>operator
  delete()</code> is replaced, care must be taken when to call this function
  in applications with hard real-time requirements</p>
  <pre>
void <a name="initiate_processor" id=
"initiate_processor">initiate_processor</a>( processor_handle processor );
</pre>

  <p><b>Requires</b>: <code>processor</code> was obtained from a call to one
  of the <code>create_processor()</code> overloads on the same
  <code>fifo_scheduler&lt;&gt;</code> object<br>
  <b>Effects</b>: Creates and passes to
  <code>FifoWorker::queue_work_item()</code> an object of type
  <code>FifoWorker::work_item</code> that, when later executed in
  <code>FifoWorker::operator()()</code>, leads to a call to <code><a href=
  "#event_processor::initiate">initiate</a>()</code> on the event processor
  object associated with <code>processor</code>. The object is silently
  discarded if the event processor object has been destructed before<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>FifoWorker::work_item()</code> and
  <code>FifoWorker::queue_work_item()</code></p>
  <pre>
void <a name="terminate_processor" id=
"terminate_processor">terminate_processor</a>( processor_handle processor );
</pre>

  <p><b>Requires</b>: <code>processor</code> was obtained from a call to one
  of the <code>create_processor&lt;&gt;()</code> overloads on the same
  <code>fifo_scheduler&lt;&gt;</code> object<br>
  <b>Effects</b>: Creates and passes to
  <code>FifoWorker::queue_work_item()</code> an object of type
  <code>FifoWorker::work_item</code> that, when later executed in
  <code>FifoWorker::operator()()</code>, leads to a call to <code><a href=
  "#event_processor::terminate">terminate</a>()</code> on the event processor
  object associated with <code>processor</code>. The object is silently
  discarded if the event processor object has been destructed before<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>FifoWorker::work_item()</code> and
  <code>FifoWorker::queue_work_item()</code></p>
  <pre>
void <a name="queue_event" id="queue_event">queue_event</a>(
  const processor_handle &amp; processor,
  const event_ptr_type &amp; pEvent );
</pre>

  <p><b>Requires</b>: <code>pEvent.get() != 0</code> and
  <code>processor</code> was obtained from a call to one of the
  <code>create_processor&lt;&gt;()</code> overloads on the same
  <code>fifo_scheduler&lt;&gt;</code> object<br>
  <b>Effects</b>: Creates and passes to
  <code>FifoWorker::queue_work_item()</code> an object of type
  <code>FifoWorker::work_item</code> that, when later executed in
  <code>FifoWorker::operator()()</code>, leads to a call to <code><a href=
  "#event_processor::process_event">process_event</a>( *pEvent )</code> on
  the event processor object associated with <code>processor</code>. The
  object is silently discarded if the event processor object has been
  destructed before<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>FifoWorker::work_item()</code> and
  <code>FifoWorker::queue_work_item()</code></p>
  <pre>
void <a name="queue_work_item" id=
"queue_work_item">queue_work_item</a>( const work_item &amp; item );
</pre>

  <p><b>Effects</b>: <code>FifoWorker::queue_work_item( item );</code><br>
  <b>Throws</b>: Any exceptions propagated from the above call</p>
  <pre>
void <a name="fifo_scheduler::terminate" id=
"fifo_scheduler::terminate">terminate</a>();
</pre>

  <p><b>Effects</b>: <code>FifoWorker::terminate()</code><br>
  <b>Throws</b>: Any exceptions propagated from the above call</p>
  <pre>
unsigned long <a name="operatorfuncall" id=
"operatorfuncall">operator()</a>( unsigned long maxEventCount = 0 );
</pre>

  <p><b>Requires</b>: Must only be called from exactly one thread<b><br>
  Effects</b>: <code>FifoWorker::operator()( maxEventCount )</code><br>
  <b>Returns</b>: The return value of the above call<br>
  <b>Throws</b>: Any exceptions propagated from the above call</p>

  <h3>Class template <code>fifo_scheduler</code> observer functions</h3>
  <pre>
bool <a name="fifo_scheduler::terminated" id=
"fifo_scheduler::terminated">terminated</a>() const;
</pre>

  <p><b>Requires</b>: Must only be called from the thread that also calls
  <code>operator()()</code><br>
  <b>Returns</b>: <code>FifoWorker::terminated();</code></p>

  <h1>Header &lt;boost/statechart/<a name="exception_translator.hpp" id=
  "exception_translator.hpp">exception_translator.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplateexception_translator" id=
  "ClassTemplateexception_translator">Class template
  <code>exception_translator</code></a></h2>

  <p>This class template is a model of the <a href=
  "#ExceptionTranslator">ExceptionTranslator</a> concept.</p>

  <h3>Class template <code>exception_translator</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "exception_translator parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>ExceptionEvent</code></td>

      <td>A model of the <a href="#Event">Event</a> concept</td>

      <td>The type of event that is dispatched when an exception
      is propagated into the framework</td>

      <td><code>exception_thrown</code></td>
    </tr>
  </table>

  <h3>Class template <code>exception_translator</code> synopsis &amp;
  semantics</h3>
  <pre>
namespace boost
{
namespace statechart
{
  class exception_thrown : public event&lt; exception_thrown &gt; {};

  template&lt; class ExceptionEvent = exception_thrown &gt;
  class exception_translator
  {
    public:
      template&lt; class Action, class ExceptionEventHandler &gt;
      result operator()(
        Action action,
        ExceptionEventHandler eventHandler )
      {
        try
        {
          return action();
        }
        catch( ... )
        {
          return eventHandler( ExceptionEvent() );
        }
      }
  };
}
}
</pre>

  <h1>Header &lt;boost/statechart/<br>
  <a name="null_exception_translator.hpp" id=
  "null_exception_translator.hpp">null_exception_translator.hpp</a>&gt;</h1>

  <h2><a name="Classnull_exception_translator" id=
  "Classnull_exception_translator">Class
  <code>null_exception_translator</code></a></h2>

  <p>This class is a model of the <a href=
  "#ExceptionTranslator">ExceptionTranslator</a> concept.</p>

  <h3>Class <code>null_exception_translator</code> synopsis &amp;
  semantics</h3>
  <pre>
namespace boost
{
namespace statechart
{
  class null_exception_translator
  {
    public:
      template&lt; class Action, class ExceptionEventHandler &gt;
      result operator()(
        Action action, ExceptionEventHandler )
      {
        return action();
      }
  };
}
}
</pre>

  <h1>Header &lt;boost/statechart/<a name="simple_state.hpp" id=
  "simple_state.hpp">simple_state.hpp</a>&gt;</h1>

  <h2><a name="Enumhistory_mode" id="Enumhistory_mode">Enum
  <code>history_mode</code></a></h2>

  <p>Defines the history type of a state.</p>
  <pre>
namespace boost
{
namespace statechart
{
  enum history_mode
  {
    has_no_history,
    has_shallow_history,
    has_deep_history,
    has_full_history // shallow &amp; deep
  };
}
}
</pre>

  <h2><a name="ClassTemplatesimple_state" id=
  "ClassTemplatesimple_state">Class template
  <code>simple_state</code></a></h2>

  <p>This is the base class template for all models of the <a href=
  "#SimpleState">SimpleState</a> concept. Such models must not call any of
  the following <code>simple_state&lt;&gt;</code> member functions from their
  constructors:</p>
  <pre>
void <b>post_event</b>(
  const intrusive_ptr&lt; const event_base &gt; &amp; );
void <b>post_event</b>( const event_base &amp; );

template&lt;
  class HistoryContext,
  <i>implementation-defined-unsigned-integer-type
</i>    orthogonalPosition &gt;
void <b>clear_shallow_history</b>();
template&lt;
  class HistoryContext,
  <i>implementation-defined-unsigned-integer-type
</i>    orthogonalPosition &gt;
void <b>clear_deep_history</b>();

outermost_context_type &amp; <b>outermost_context</b>();
const outermost_context_type &amp; <b>outermost_context</b>() const;

template&lt; class OtherContext &gt;
OtherContext &amp; <b>context</b>();
template&lt; class OtherContext &gt;
const OtherContext &amp; <b>context</b>() const;

template&lt; class Target &gt;
Target <b>state_cast</b>() const;
template&lt; class Target &gt;
Target <b>state_downcast</b>() const;

state_iterator <b>state_begin</b>() const;
state_iterator <b>state_end</b>() const;

const event_base * <b>triggering_event</b>() const;
</pre>

  <p>States that need to call any of these member functions from their
  constructors must derive from the <code><a href=
  "#ClassTemplatestate">state</a></code> class template.</p>

  <h3>Class template <code>simple_state</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "simple_state parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>MostDerived</code></td>

      <td>The most-derived subtype of this class template</td>

      <td>&nbsp;</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>Context</code></td>

      <td>A most-derived direct or indirect subtype of the
      <code><a href="#ClassTemplatestate_machine">state_machine</a></code> or
      <code><a href=
      "#ClassTemplateasynchronous_state_machine">asynchronous_state_machine</a></code>
      class templates or a model of the <a href=
      "#SimpleState">SimpleState</a> or <a href="#State">State</a> concepts
      or an instantiation of the <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;::orthogonal</a></code>
      class template. Must be a complete type</td>

      <td>Defines the states' position in the state
      hierarchy</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>InnerInitial</code></td>

      <td>An <code>mpl::list&lt;&gt;</code> containing models of
      the <a href="#SimpleState">SimpleState</a> or <a href=
      "#State">State</a> concepts or instantiations of the <code><a href=
      "#ClassTemplateshallow_history">shallow_history</a></code> or
      <code><a href="#ClassTemplatedeep_history">deep_history</a></code>
      class templates. If there is only a single inner initial state that is
      not a template instantiation then it can also be passed directly,
      without wrapping it into an <code>mpl::list&lt;&gt;</code>. The
      <code>Context</code> argument passed to the <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base
      of&nbsp;each state in the list must correspond to the orthogonal region
      it belongs to. That is, the first state in the list must pass
      <code>MostDerived::orthogonal&lt; 0 &gt;</code>, the second
      <code>MostDerived::orthogonal&lt; 1 &gt;</code> and so forth.
      <code>MostDerived::orthogonal&lt; 0 &gt;</code> and
      <code>MostDerived</code> are synonymous</td>

      <td>Defines the inner initial state for each orthogonal
      region. By default, a state does not have inner states</td>

      <td><i><code>unspecified</code></i></td>
    </tr>

    <tr>
      <td><code>historyMode</code></td>

      <td>One of the values defined in the <code><a href=
      "#Enumhistory_mode">history_mode</a></code> enumeration</td>

      <td>Defines whether the state saves shallow, deep or both
      histories upon exit</td>

      <td><code>has_no_history</code></td>
    </tr>
  </table>

  <h3>Class template <code>simple_state</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class MostDerived,
    class Context,
    class InnerInitial = <i>unspecified</i>,
    history_mode historyMode = has_no_history &gt;
  class simple_state : <i>implementation-defined</i>
  {
    public:
      // by default, a state has no reactions
      typedef mpl::list&lt;&gt; reactions;

      // see template parameters
      template&lt; <i>implementation-defined-unsigned-integer-type
</i>        innerOrthogonalPosition &gt;
      struct orthogonal
      {
        // <i>implementation-defined</i>
      };

      typedef typename Context::outermost_context_type
        outermost_context_type;

      outermost_context_type &amp; <a href=
"#outermost_context">outermost_context</a>();
      const outermost_context_type &amp; <a href=
"#outermost_contextconst">outermost_context</a>() const;

      template&lt; class OtherContext &gt;
      OtherContext &amp; <a href="#context">context</a>();
      template&lt; class OtherContext &gt;
      const OtherContext &amp; <a href="#contextconst">context</a>() const;

      template&lt; class Target &gt;
      Target <a href="#simple_state::state_cast">state_cast</a>() const;
      template&lt; class Target &gt;
      Target <a href=
"#simple_state::state_downcast">state_downcast</a>() const;

      // a model of the StateBase concept
      typedef <i>implementation-defined</i> state_base_type;
      // a model of the standard Forward Iterator concept
      typedef <i>implementation-defined</i> state_iterator;

      state_iterator <a href=
"#simple_state::state_begin">state_begin</a>() const;
      state_iterator <a href=
"#simple_state::state_end">state_end</a>() const;

      const event_base * <a href="#triggering_event0">triggering_event</a>() const;

      void <a href="#post_event0">post_event</a>(
        const intrusive_ptr&lt; const <a href=
"#Classevent_base">event_base</a> &gt; &amp; );
      void <a href="#post_event1">post_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; );

      <a href="#Classresult">result</a> <a href=
"#discard_event">discard_event</a>();
      <a href="#Classresult">result</a> <a href=
"#forward_event">forward_event</a>();
      <a href="#Classresult">result</a> <a href=
"#defer_event">defer_event</a>();
      template&lt; class DestinationState &gt;
      <a href="#Classresult">result</a> <a href="#transit1">transit</a>();
      template&lt;
        class DestinationState,
        class TransitionContext,
        class Event &gt;
      <a href="#Classresult">result</a> <a href="#transit2">transit</a>(
        void ( TransitionContext::* )( const Event &amp; ),
        const Event &amp; );
      <a href="#Classresult">result</a> <a href=
"#simple_state::terminate">terminate</a>();

      template&lt;
        class HistoryContext,
        <i>implementation-defined-unsigned-integer-type
</i>          orthogonalPosition &gt;
      void <a href="#clear_shallow_history">clear_shallow_history</a>();
      template&lt;
        class HistoryContext,
        <i>implementation-defined-unsigned-integer-type
</i>          orthogonalPosition &gt;
      void <a href="#clear_deep_history">clear_deep_history</a>();

      static id_type <a href="#static_type">static_type</a>();

      template&lt; class CustomId &gt;
      static const CustomId * <a href=
"#custom_static_type_ptr">custom_static_type_ptr</a>();

      template&lt; class CustomId &gt;
      static void <a href=
"#custom_static_type_ptr1">custom_static_type_ptr</a>( const CustomId * );

      // see <a href="#transit1">transit</a>() or <a href=
"#simple_state::terminate">terminate</a>() effects
      void exit() {}

    protected:
      <a href="#simple_state">simple_state</a>();
      <a href="#simple_statedtor">~simple_state</a>();
  };
}
}
</pre>

  <h3>Class template <code>simple_state</code> constructor and
  destructor</h3>
  <pre>
<a name="simple_state" id="simple_state">simple_state</a>();
</pre>

  <p><b>Effects</b>: Constructs a state object</p>
  <pre>
<a name="simple_statedtor" id="simple_statedtor">~simple_state</a>();
</pre>

  <p><b>Effects</b>: If the state has deferral reactions of which at least
  one has been triggered during the lifetime of the state then the contents
  of the deferred events queue is moved to the front of the posted events
  queue.</p>

  <h3>Class template <code>simple_state</code> modifier functions</h3>
  <pre>
void <a name="post_event0" id="post_event0">post_event</a>(
  const intrusive_ptr&lt; const <a href=
"#Classevent_base">event_base</a> &gt; &amp; pEvt );
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template<b>.</b> All direct and indirect
  callers must be exception-neutral<b><br>
  Effects</b>: <a href=
  "#outermost_context"><code>outermost_context</code></a><code>().<a href=
  "#post_event2">post_event</a>( pEvt );</code><br>
  <b>Throws</b>: Whatever the above call throws</p>
  <pre>
void <a name="post_event1" id="post_event1">post_event</a>( const <a href=
"#Classevent_base">event_base</a> &amp; evt );
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template<b>.</b> All direct and indirect
  callers must be exception-neutral<b><br>
  Effects</b>: <a href=
  "#outermost_context"><code>outermost_context</code></a><code>().<a href=
  "#post_event3">post_event</a>( evt );</code><br>
  <b>Throws</b>: Whatever the above call throws</p>
  <pre>
<a href="#Classresult">result</a> <a name="discard_event" id=
"discard_event">discard_event</a>();
</pre>

  <p><b>Requires</b>: Must only be called from within <code>react</code>
  member functions, which are called by <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction&lt;&gt;</a></code>
  instantiations. All direct and indirect callers must be
  exception-neutral<br>
  <b>Effects</b>: Instructs the state machine to discard the current event
  and to continue with the processing of the remaining events (see
  <code><a href=
  "#process_event">state_machine&lt;&gt;::process_event</a>()</code> for
  details)<br>
  <b>Returns</b>: A <code><a href="#Classresult">result</a></code> object.
  The user-supplied <code>react</code> member function must return this
  object to its caller</p>
  <pre>
<a href="#Classresult">result</a> <a name="forward_event" id=
"forward_event">forward_event</a>();
</pre>

  <p><b>Requires</b>: Must only be called from within <code>react</code>
  member functions, which are called by <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction&lt;&gt;</a></code>
  instantiations. All direct and indirect callers must be
  exception-neutral<br>
  <b>Effects</b>: Instructs the state machine to forward the current event to
  the next state (see <code><a href=
  "#process_event">state_machine&lt;&gt;::process_event</a>()</code> for
  details)<br>
  <b>Returns</b>: A <code><a href="#Classresult">result</a></code> object.
  The user-supplied <code>react</code> member function must return this
  object to its caller</p>
  <pre>
<a href="#Classresult">result</a> <a name="defer_event" id=
"defer_event">defer_event</a>();
</pre>

  <p><b>Requires</b>: Must only be called from within <code>react</code>
  member functions, which are called by <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction&lt;&gt;</a></code>
  instantiations. All direct and indirect callers must be
  exception-neutral<br>
  <b>Effects</b>: Instructs the state machine to defer the current event and
  to continue with the processing of the remaining events (see <code><a href=
  "#process_event">state_machine&lt;&gt;::process_event</a>()</code> for
  details)<br>
  <b>Returns</b>: A <code><a href="#Classresult">result</a></code> object.
  The user-supplied <code>react</code> member function must return this
  object to its caller<br>
  <b>Throws</b>: Any exceptions propagated from
  <code>Allocator::rebind&lt;&gt;::other::allocate()</code> (the template
  parameter passed to the base class of
  <code>outermost_context_type</code>)</p>
  <pre>
template&lt; class DestinationState &gt;
<a href="#Classresult">result</a> <a name="transit1" id=
"transit1">transit</a>();
</pre>

  <p><b>Requires</b>: Must only be called from within <code>react</code>
  member functions, which are called by <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction&lt;&gt;</a></code>
  instantiations. All direct and indirect callers must be
  exception-neutral<br>
  <b>Effects</b>:</p>

  <ol>
    <li>Exits all currently active direct and indirect inner states of the
    innermost common context of this state and <code>DestinationState</code>.
    Innermost states are exited first. Other states are exited as soon as all
    their direct and indirect inner states have been exited. The inner states
    of each state are exited according to the number of their orthogonal
    region. The state in the orthogonal region with the highest number is
    always exited first, then the state in the region with the second-highest
    number and so on.<br>
      The process of exiting a state consists of the following steps:

      <ol>
        <li>If there is an exception pending that has not yet been handled
        successfully then only step 5 is executed</li>

        <li>Calls the <code>exit</code> member function (see <a href=
        "#ClassTemplatesimple_state">synopsis</a>) of the most-derived state
        object. If <code>exit()</code> throws then steps 3 and 4 are not
        executed</li>

        <li>If the state has shallow history then shallow history information
        is saved</li>

        <li>If the state is an innermost state then deep history information
        is saved for all direct and indirect outer states that have deep
        history</li>

        <li>The state object is destructed</li>
      </ol>
    </li>

    <li>Enters (constructs) the state that is both a direct inner state of
    the innermost common context and either the <code>DestinationState</code>
    itself or a direct or indirect outer state of
    <code>DestinationState</code></li>

    <li>Enters (constructs) the tree formed by the direct and indirect inner
    states of the previously entered state down to the
    <code>DestinationState</code> and beyond depth first. The inner states of
    each state are entered according to the number of their orthogonal
    region. The state in orthogonal region 0 is always entered first, then
    the state in region 1 and so on</li>

    <li>Instructs the state machine to discard the current event and to
    continue with the processing of the remaining events (see <code><a href=
    "#process_event">state_machine&lt;&gt;::process_event</a>()</code> for
    details)</li>
  </ol>

  <p><b>Returns</b>: A <code><a href="#Classresult">result</a></code> object.
  The user-supplied <code>react</code> member function must return this
  object to its caller<br>
  <b>Throws</b>: Any exceptions propagated from:</p>

  <ul>
    <li><code>Allocator::rebind&lt;&gt;::other::allocate()</code> (the
    template parameter passed to the base class of
    <code>outermost_context_type</code>)</li>

    <li>state constructors</li>

    <li><code>exit</code> member functions</li>
  </ul>

  <p><b>Caution</b>: Inevitably destructs this state before returning to the
  calling <code>react</code> member function, which must therefore not
  attempt to access anything except stack objects before returning to its
  caller</p>
  <pre>
template&lt;
  class DestinationState,
  class TransitionContext,
  class Event &gt;
<a href="#Classresult">result</a> <a name="transit2" id=
"transit2">transit</a>(
  void ( TransitionContext::* )( const Event &amp; ),
  const Event &amp; );
</pre>

  <p><b>Requires</b>: Must only be called from within <code>react</code>
  member functions, which are called by <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction&lt;&gt;</a></code>
  instantiations. All direct and indirect callers must be
  exception-neutral<br>
  <b>Effects</b>:</p>

  <ol>
    <li>Exits all currently active direct and indirect inner states of the
    innermost common context of this state and <code>DestinationState</code>.
    Innermost states are exited first. Other states are exited as soon as all
    their direct and indirect inner states have been exited. The inner states
    of each state are exited according to the number of their orthogonal
    region. The state in the orthogonal region with the highest number is
    always exited first, then the state in the region with the second-highest
    number and so on.<br>
      The process of exiting a state consists of the following steps:

      <ol>
        <li>If there is an exception pending that has not yet been handled
        successfully then only step 5 is executed</li>

        <li>Calls the <code>exit</code> member function (see <a href=
        "#ClassTemplatesimple_state">synopsis</a>) of the most-derived state
        object. If <code>exit()</code> throws then steps 3 and 4 are not
        executed</li>

        <li>If the state has shallow history then shallow history information
        is saved</li>

        <li>If the state is an innermost state then deep history information
        is saved for all direct and indirect outer states that have deep
        history</li>

        <li>The state object is destructed</li>
      </ol>
    </li>

    <li>Executes the passed transition action, forwarding the passed
    event</li>

    <li>Enters (constructs) the state that is both a direct inner state of
    the innermost common context and either the <code>DestinationState</code>
    itself or a direct or indirect outer state of
    <code>DestinationState</code></li>

    <li>Enters (constructs) the tree formed by the direct and indirect inner
    states of the previously entered state down to the
    <code>DestinationState</code> and beyond depth first. The inner states of
    each state are entered according to the number of their orthogonal
    region. The state in orthogonal region 0 is always entered first, then
    the state in region 1 and so on</li>

    <li>Instructs the state machine to discard the current event and to
    continue with the processing of the remaining events (see <code><a href=
    "#process_event">state_machine&lt;&gt;::process_event</a>()</code> for
    details)</li>
  </ol>

  <p><b>Returns</b>: A <code><a href="#Classresult">result</a></code> object.
  The user-supplied <code>react</code> member function must return this
  object to its caller<br>
  <b>Throws</b>: Any exceptions propagated from:</p>

  <ul>
    <li><code>Allocator::rebind&lt;&gt;::other::allocate()</code> (the
    template parameter passed to the base class of
    <code>outermost_context_type</code>)</li>

    <li>state constructors</li>

    <li><code>exit</code> member functions</li>

    <li>the transition action</li>
  </ul>

  <p><b>Caution</b>: Inevitably destructs this state before returning to the
  calling <code>react</code> member function, which must therefore not
  attempt to access anything except stack objects before returning to its
  caller</p>
  <pre>
<a href="#Classresult">result</a> <a name="simple_state::terminate" id=
"simple_state::terminate">terminate</a>();
</pre>

  <p><b>Requires</b>: Must only be called from within <code>react</code>
  member functions, which are called by <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction&lt;&gt;</a></code>
  instantiations. All direct and indirect callers must be
  exception-neutral<br>
  <b>Effects</b>: Exits this state and all its direct and indirect inner
  states. Innermost states are exited first. Other states are exited as soon
  as all their direct and indirect inner states have been exited. The inner
  states of each state are exited according to the number of their orthogonal
  region. The state in the orthogonal region with the highest number is
  always exited first, then the state in the region with the second-highest
  number and so on.<br>
  The process of exiting a state consists of the following steps:</p>

  <ol>
    <li>If there is an exception pending that has not yet been handled
    successfully then only step 5 is executed</li>

    <li>Calls the <code>exit</code> member function (see <a href=
    "#ClassTemplatesimple_state">synopsis</a>) of the most-derived state
    object. If <code>exit()</code> throws then steps 3 and 4 are not
    executed</li>

    <li>If the state has shallow history then shallow history information is
    saved</li>

    <li>If the state is an innermost state then deep history information is
    saved for all direct and indirect outer states that have deep
    history</li>

    <li>The state object is destructed</li>
  </ol>

  <p>Also instructs the state machine to discard the current event and to
  continue with the processing of the remaining events (see <code><a href=
  "#process_event">state_machine&lt;&gt;::process_event</a>()</code> for
  details)<br>
  <b>Returns</b>: A <code><a href="#Classresult">result</a></code> object.
  The user-supplied <code>react</code> member function must return this
  object to its caller<br>
  <b>Throws</b>: Any exceptions propagated from:</p>

  <ul>
    <li><code>Allocator::rebind&lt;&gt;::other::allocate()</code> (the
    template parameter passed to the base class of
    <code>outermost_context_type</code>, used to allocate space to save
    history)</li>

    <li><code>exit</code> member functions</li>
  </ul>

  <p><b>Note</b>: If this state is the only currently active inner state of
  its direct outer state then the direct outer state is terminated also. The
  same applies recursively for all indirect outer states<br>
  <b>Caution</b>: Inevitably destructs this state before returning to the
  calling <code>react</code> member function, which must therefore not
  attempt to access anything except stack objects before returning to its
  caller</p>
  <pre>
template&lt;
  class HistoryContext,
  <i>implementation-defined-unsigned-integer-type
</i>    orthogonalPosition &gt;
void <a name="clear_shallow_history" id=
"clear_shallow_history">clear_shallow_history</a>();
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. The <code>historyMode</code>
  argument passed to the <code><a href=
  "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
  <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base
  of&nbsp;<code>HistoryContext</code> must be equal to
  <code>has_shallow_history</code> or <code>has_full_history</code><br>
  <b>Effects</b>: Clears the shallow history of the orthogonal region
  specified by <code>orthogonalPosition</code> of the state specified by
  <code>HistoryContext</code><br>
  <b>Throws</b>: Any exceptions propagated from
  <code>Allocator::rebind&lt;&gt;::other::allocate()</code> (the template
  parameter passed to the base class of
  <code>outermost_context_type</code>)</p>
  <pre>
template&lt;
  class HistoryContext,
  <i>implementation-defined-unsigned-integer-type
</i>    orthogonalPosition &gt;
void <a name="clear_deep_history" id=
"clear_deep_history">clear_deep_history</a>();
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. The <code>historyMode</code>
  argument passed to the <code><a href=
  "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
  <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base
  of&nbsp;<code>HistoryContext</code> must be equal to
  <code>has_deep_history</code> or <code>has_full_history</code><br>
  <b>Effects</b>: Clears the deep history of the orthogonal region specified
  by <code>orthogonalPosition</code> of the state specified by
  <code>HistoryContext</code><br>
  <b>Throws</b>: Any exceptions propagated from
  <code>Allocator::rebind&lt;&gt;::other::allocate()</code> (the template
  parameter passed to the base class of
  <code>outermost_context_type</code>)</p>

  <h3>Class template <code>simple_state</code> observer functions</h3>
  <pre>
outermost_context_type &amp; <a name="outermost_context" id=
"outermost_context">outermost_context</a>();
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. If called from a destructor of a
  direct or indirect subtype then the <code>state_machine&lt;&gt;</code> subclass
  portion must still exist<br>
  <b>Returns</b>: A reference to the outermost context, which is always the
  state machine this state belongs to<br></p>
  <pre>
const outermost_context_type &amp; <a name="outermost_contextconst" id=
"outermost_contextconst">outermost_context() const</a>;
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. If called from a destructor of a
  direct or indirect subtype then the <code>state_machine&lt;&gt;</code> subclass
  portion must still exist<br>
  <b>Returns</b>: A reference to the const outermost context, which is always
  the state machine this state belongs to</p>
  <pre>
template&lt; class OtherContext &gt;
OtherContext &amp; <a name="context" id="context">context</a>();
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. If called from a destructor of a
  direct or indirect subtype with a <code>state_machine&lt;&gt;</code> subtype as
  argument then the <code>state_machine&lt;&gt;</code> subclass portion must still
  exist<br>
  <b>Returns</b>: A reference to a direct or indirect context or any public base
  type of the contexts</p>
  <pre>
template&lt; class OtherContext &gt;
const OtherContext &amp; <a name="contextconst" id=
"contextconst">context() const</a>;
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. If called from a destructor of a
  direct or indirect subtype with a <code>state_machine&lt;&gt;</code> subtype as
  argument then the <code>state_machine&lt;&gt;</code> subclass portion must still
  exist<br>
  <b>Returns</b>: A reference to a const direct or indirect context or any public
  base type of the contexts</p>
  <pre>
template&lt; class Target &gt;
Target <a name="simple_state::state_cast" id=
"simple_state::state_cast">state_cast</a>() const;
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template<b><br>
  Returns</b>: Has exactly the same semantics as <code><a href=
  "#state_cast">state_machine&lt;&gt;::state_cast</a>&lt;&gt;()</code><br>
  <b>Throws</b>: Has exactly the same semantics as <code><a href=
  "#state_cast">state_machine&lt;&gt;::state_cast</a>&lt;&gt;()</code><b><br>
  Note</b>: The result is <b>unspecified</b> if this function is called when
  the machine is <a href=
  "definitions.html#UnstableStateMachine">unstable</a></p>
  <pre>
template&lt; class Target &gt;
Target <a name="simple_state::state_downcast" id=
"simple_state::state_downcast">state_downcast</a>() const;
</pre>

  <p><b>Requires</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template. Moreover, <code><a href=
  "#state_downcast">state_machine&lt;&gt;::state_downcast</a>&lt;&gt;()</code>
  requirements also apply<br>
  <b>Returns</b>: Has exactly the same semantics as <code><a href=
  "#state_downcast">state_machine&lt;&gt;::state_downcast</a>&lt;&gt;()</code><br>

  <b>Throws</b>: Has exactly the same semantics as <code><a href=
  "#state_downcast">state_machine&lt;&gt;::state_downcast</a>&lt;&gt;()</code><b><br>

  Note</b>: The result is <b>unspecified</b> if this function is called when
  the machine is <a href=
  "definitions.html#UnstableStateMachine">unstable</a></p>
  <pre>
state_iterator <a name="simple_state::state_begin" id=
"simple_state::state_begin">state_begin</a>() const;
</pre>
  <pre>
state_iterator <a name="simple_state::state_end" id=
"simple_state::state_end">state_end</a>() const;
</pre>

  <p><b>Require</b>: If called from a constructor of a direct or indirect
  subtype then the most-derived type must directly or indirectly derive from
  the <code>state</code> class template<b><br>
  Return</b>: Have exactly the same semantics as <code><a href=
  "#state_begin">state_machine&lt;&gt;::state_begin</a>()</code> and
  <code><a href=
  "#state_end">state_machine&lt;&gt;::state_end</a>()</code><br>
  <b>Note</b>: The result is <b>unspecified</b> if these functions are called
  when the machine is <a href=
  "definitions.html#UnstableStateMachine">unstable</a></p>
  <pre>
const event_base * <a name="triggering_event0" id="triggering_event0">triggering_event</a>();
</pre>

  <p><b>Returns</b>: Has exactly the same semantics as
  <code><a href="#triggering_event1">state_machine&lt;&gt;::triggering_event</a>()</code></p>

  <h3>Class template <code>simple_state</code> static functions</h3>
  <pre>
static id_type <a name="static_type" id="static_type">static_type</a>();
</pre>

  <p><b>Returns</b>: A value unambiguously identifying the type of
  <code>MostDerived</code><br>
  <b>Note</b>: <code>id_type</code> values are comparable with
  <code>operator==()</code> and <code>operator!=()</code>. An unspecified
  collating order can be established with <code>std::less&lt; id_type
  &gt;</code></p>
  <pre>
template&lt; class CustomId &gt;
static const CustomId * <a name="custom_static_type_ptr" id=
"custom_static_type_ptr">custom_static_type_ptr</a>();
</pre>

  <p><b>Requires</b>: If a custom type identifier has been set then
  <code>CustomId</code> must match the type of the previously set
  pointer<b><br>
  Returns</b>: The pointer to the custom type identifier for
  <code>MostDerived</code> or <code>0</code><br>
  <b>Note</b>: This function is not available if <a href=
  "configuration.html#ApplicationDefinedMacros"><code>BOOST_STATECHART_USE_NATIVE_RTTI</code></a>
  is defined</p>
  <pre>
template&lt; class CustomId &gt;
static void <a name="custom_static_type_ptr1" id=
"custom_static_type_ptr1">custom_static_type_ptr( const CustomId * )</a>;
</pre>

  <p><b>Effects</b>: Sets the pointer to the custom type identifier for
  <code>MostDerived</code><br>
  <b>Note</b>: This function is not available if <a href=
  "configuration.html#ApplicationDefinedMacros"><code>BOOST_STATECHART_USE_NATIVE_RTTI</code></a>
  is defined</p>

  <h1>Header &lt;boost/statechart/<a name="state.hpp" id=
  "state.hpp">state.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatestate" id="ClassTemplatestate">Class template
  <code>state</code></a></h2>

  <p>This is the base class template for all models of the <a href=
  "#State">State</a> concept. Such models typically need to call at least one
  of the following <code><a href=
  "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> member
  functions from their constructors:</p>
  <pre>
void <b>post_event</b>(
  const intrusive_ptr&lt; const event_base &gt; &amp; );
void <b>post_event</b>( const event_base &amp; );

template&lt;
  class HistoryContext,
  <i>implementation-defined-unsigned-integer-type
</i>    orthogonalPosition &gt;
void <b>clear_shallow_history</b>();
template&lt;
  class HistoryContext,
  <i>implementation-defined-unsigned-integer-type
</i>    orthogonalPosition &gt;
void <b>clear_deep_history</b>();

outermost_context_type &amp; <b>outermost_context</b>();
const outermost_context_type &amp; <b>outermost_context</b>() const;

template&lt; class OtherContext &gt;
OtherContext &amp; <b>context</b>();
template&lt; class OtherContext &gt;
const OtherContext &amp; <b>context</b>() const;

template&lt; class Target &gt;
Target <b>state_cast</b>() const;
template&lt; class Target &gt;
Target <b>state_downcast</b>() const;

state_iterator <b>state_begin</b>() const;
state_iterator <b>state_end</b>() const;
const event_base * <b>triggering_event</b>() const;
</pre>

  <p>States that do not need to call any of these member functions from their
  constructors should rather derive from the <code><a href=
  "#ClassTemplatesimple_state">simple_state</a></code> class template, what
  saves the implementation of the forwarding constructor.</p>

  <h3>Class template <code>state</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class MostDerived,
    class Context,
    class InnerInitial = <i>unspecified</i>,
    history_mode historyMode = has_no_history &gt;
  class state : public simple_state&lt;
    MostDerived, Context, InnerInitial, historyMode &gt;
  {
    protected:
      struct my_context
      {
        // <i>implementation-defined</i>
      };

      typedef state my_base;

      state( my_context ctx );
      ~state();
  };
}
}
</pre>

  <p>Direct and indirect subtypes of <code>state&lt;&gt;</code> must provide
  a constructor with the same signature as the <code>state&lt;&gt;</code>
  constructor, forwarding the context parameter.</p>

  <h1>Header &lt;boost/statechart/<a name="shallow_history.hpp" id=
  "shallow_history.hpp">shallow_history.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplateshallow_history" id=
  "ClassTemplateshallow_history">Class template
  <code>shallow_history</code></a></h2>

  <p>This class template is used to specify a shallow history transition
  target or a shallow history inner initial state.</p>

  <h3>Class template <code>shallow_history</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "shallow_history parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>
    </tr>

    <tr>
      <td><code>DefaultState</code></td>

      <td>A model of the <a href="#SimpleState">SimpleState</a>
      or <a href="#State">State</a> concepts. The type passed as
      <code>Context</code> argument to the <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base
      of&nbsp;<code>DefaultState</code> must itself pass
      <code>has_shallow_history</code> or <code>has_full_history</code> as
      <code>historyMode</code> argument to its <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base</td>

      <td>The state that is entered if shallow history is not available</td>
    </tr>
  </table>

  <h3>Class template <code>shallow_history</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class DefaultState &gt;
  class shallow_history
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h1>Header &lt;boost/statechart/<a name="deep_history.hpp" id=
  "deep_history.hpp">deep_history.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatedeep_history" id=
  "ClassTemplatedeep_history">Class template
  <code>deep_history</code></a></h2>

  <p>This class template is used to specify a deep history transition target
  or a deep history inner initial state. The current deep history
  implementation has some <a href=
  "rationale.html#Limitations">limitations</a>.</p>

  <h3>Class template <code>deep_history</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "deep_history parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>
    </tr>

    <tr>
      <td><code>DefaultState</code></td>

      <td>A model of the <a href="#SimpleState">SimpleState</a>
      or <a href="#State">State</a> concepts. The type passed as
      <code>Context</code> argument to the <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base
      of&nbsp;<code>DefaultState</code> must itself pass
      <code>has_deep_history</code> or <code>has_full_history</code> as
      <code>historyMode</code> argument to its <code><a href=
      "#ClassTemplatesimple_state">simple_state&lt;&gt;</a></code> or
      <code><a href="#ClassTemplatestate">state&lt;&gt;</a></code> base</td>

      <td>The state that is entered if deep history is not available</td>
    </tr>
  </table>

  <h3>Class template <code>deep_history</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class DefaultState &gt;
  class deep_history
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h1>Header &lt;boost/statechart/<a name="event_base.hpp" id=
  "event_base.hpp">event_base.hpp</a>&gt;</h1>

  <h2><a name="Classevent_base" id="Classevent_base">Class
  <code>event_base</code></a></h2>

  <p>This is the common base of all events.</p>

  <h3>Class <code>event_base</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  class event_base
  {
    public:
      intrusive_ptr&lt; const event_base &gt;
        <a href="#intrusive_from_this">intrusive_from_this</a>() const;

      typedef <i>implementation-defined</i> id_type;

      id_type <a href="#event_base::dynamic_type">dynamic_type</a>() const;

      template&lt; typename CustomId &gt;
      const CustomId * <a href=
"#event_base::custom_dynamic_type_ptr">custom_dynamic_type_ptr</a>() const;
      
    protected:
      <a href="#event_base">event_base</a>( <i>unspecified-parameter </i>);
      virtual <a href="#event_basedtor">~event_base</a>();
  };
}
}
</pre>

  <h3>Class <code>event_base</code> constructor and destructor</h3>
  <pre>
<a name="event_base" id=
"event_base">event_base</a>( <i>unspecified-parameter </i>);
</pre>

  <p><b>Effects</b>: Constructs the common base portion of an event</p>
  <pre>
virtual <a name="event_basedtor" id="event_basedtor">~event_base</a>();
</pre>

  <p><b>Effects</b>: Destructs the common base portion of an event</p>

  <h3>Class <code>event_base</code> observer functions</h3>
  <pre>
intrusive_ptr&lt; const event_base &gt; <a name="intrusive_from_this" id=
"intrusive_from_this">intrusive_from_this</a>() const;
</pre>

  <p><b>Returns</b>: Another <code>intrusive_ptr&lt; const event_base
  &gt;</code> referencing <code>this</code> <b>if</b> <code>this</code> is
  already referenced by an <code>intrusive_ptr&lt;&gt;</code>. Otherwise,
  returns an <code>intrusive_ptr&lt; const event_base &gt;</code> referencing
  a newly created copy of the most-derived object</p>
  <pre>
id_type <a name="event_base::dynamic_type" id=
"event_base::dynamic_type">dynamic_type</a>() const;
</pre>

  <p><b>Returns</b>: A value unambiguously identifying the most-derived
  type<br>
  <b>Note</b>: <code>id_type</code> values are comparable with
  <code>operator==()</code> and <code>operator!=()</code>. An unspecified
  collating order can be established with <code>std::less&lt; id_type
  &gt;</code>. In contrast to <code>typeid( cs )</code>, this function is
  available even on platforms that do not support C++ RTTI (or have been
  configured to not support it)</p>
  <pre>
template&lt; typename CustomId &gt;
const CustomId * <a name="event_base::custom_dynamic_type_ptr" id=
"event_base::custom_dynamic_type_ptr">custom_dynamic_type_ptr</a>() const;
</pre>

  <p><b>Requires</b>: If a custom type identifier has been set then
  <code>CustomId</code> must match the type of the previously set
  pointer<b><br>
  Returns</b>: A pointer to the custom type identifier or <code>0</code><br>
  <b>Note</b>: This function is not available if <a href=
  "configuration.html#ApplicationDefinedMacros"><code>BOOST_STATECHART_USE_NATIVE_RTTI</code></a>
  is defined</p>

  <h1>Header &lt;boost/statechart/<a name="event.hpp" id=
  "event.hpp">event.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplateevent" id="ClassTemplateevent">Class template
  <code>event</code></a></h2>

  <p>This is the base class template of all events.</p>

  <h3>Class template <code>event</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary="event parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>MostDerived</code></td>

      <td>The most-derived subtype of this class template</td>

      <td>&nbsp;</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>Allocator</code></td>

      <td>A model of the standard Allocator concept</td>

      <td><code>Allocator::rebind&lt; MostDerived
      &gt;::other</code> is used to allocate and deallocate all event subtype
      objects of dynamic storage duration, see <code><a href=
      "#event::operatornew">operator new</a></code></td>

      <td><code>std::allocator&lt; void &gt;</code></td>
    </tr>
  </table>

  <h3>Class template <code>event</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class MostDerived, class Allocator = std::allocator&lt; void &gt; &gt;
  class event : <i>implementation-defined</i>
  {
    public:
      static void * <a href=
"#event::operatornew">operator new</a>( std::size_t size );
      static void * <a href=
"#event::operatornew2">operator new</a>( std::size_t size, void * p );
      static void <a href=
"#event::operatordelete">operator delete</a>( void * pEvent );

      static id_type <a href="#event::static_type">static_type</a>();

      template&lt; class CustomId &gt;
      static const CustomId * <a href=
"#event::custom_static_type_ptr">custom_static_type_ptr</a>();

      template&lt; class CustomId &gt;
      static void <a href=
"#event::custom_static_type_ptr1">custom_static_type_ptr</a>( const CustomId * );

    protected:
      <a href="#event::event">event</a>();
      virtual <a href="#eventdtor">~event</a>();
  };
}
}
</pre>

  <h3>Class template <code>event</code> constructor and destructor</h3>
  <pre>
<a name="event::event" id="event::event">event</a>();
</pre>

  <p><b>Effects</b>: Constructs an event</p>
  <pre>
virtual <a name="eventdtor" id="eventdtor">~event</a>();
</pre>

  <p><b>Effects</b>: Destructs an event</p>

  <h3>Class template <code>event</code> static functions</h3>
  <pre>
static void * <a name="event::operatornew" id=
"event::operatornew">operator new</a>( std::size_t size );
</pre>

  <p><b>Effects</b>: <code>Allocator::rebind&lt; MostDerived
  &gt;::other().allocate( 1, static_cast&lt; MostDerived * &gt;( 0 )
  );</code><br>
  <b>Returns</b>: The return value of the above call<br>
  <b>Throws</b>: Whatever the above call throws</p>
  <pre>
static void * <a name="event::operatornew2" id=
"event::operatornew2">operator new</a>( std::size_t size, void * p );
</pre>

  <p><b>Effects</b>: None<br>
  <b>Returns</b>: <code>p</code></p>
  <pre>
static void <a name="event::operatordelete" id=
"event::operatordelete">operator delete</a>( void * pEvent );
</pre>

  <p><b>Effects</b>: <code>Allocator::rebind&lt; MostDerived
  &gt;::other().deallocate( static_cast&lt; MostDerived * &gt;( pEvent ), 1
  );</code></p>
  <pre>
static id_type <a name="event::static_type" id=
"event::static_type">static_type</a>();
</pre>

  <p><b>Returns</b>: A value unambiguously identifying the type of
  <code>MostDerived</code><br>
  <b>Note</b>: <code>id_type</code> values are comparable with
  <code>operator==()</code> and <code>operator!=()</code>. An unspecified
  collating order can be established with <code>std::less&lt; id_type
  &gt;</code></p>
  <pre>
template&lt; class CustomId &gt;
static const CustomId * <a name="event::custom_static_type_ptr" id=
"event::custom_static_type_ptr">custom_static_type_ptr</a>();
</pre>

  <p><b>Requires</b>: If a custom type identifier has been set then
  <code>CustomId</code> must match the type of the previously set
  pointer<b><br>
  Returns</b>: The pointer to the custom type identifier for
  <code>MostDerived</code> or <code>0</code><br>
  <b>Note</b>: This function is not available if <a href=
  "configuration.html#ApplicationDefinedMacros"><code>BOOST_STATECHART_USE_NATIVE_RTTI</code></a>
  is defined</p>
  <pre>
template&lt; class CustomId &gt;
static void <a name="event::custom_static_type_ptr1" id=
"event::custom_static_type_ptr1">custom_static_type_ptr( const CustomId * )</a>;
</pre>

  <p><b>Effects</b>: Sets the pointer to the custom type identifier for
  <code>MostDerived</code><br>
  <b>Note</b>: This function is not available if <a href=
  "configuration.html#ApplicationDefinedMacros"><code>BOOST_STATECHART_USE_NATIVE_RTTI</code></a>
  is defined</p>

  <h1>Header &lt;boost/statechart/<a name="transition.hpp" id=
  "transition.hpp">transition.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatetransition" id="ClassTemplatetransition">Class
  template <code>transition</code></a></h2>

  <p>This class template is used to specify a transition reaction.
  Instantiations of this template can appear in the <code>reactions</code>
  member <code>typedef</code> in models of the <a href=
  "#SimpleState">SimpleState</a> and <a href="#State">State</a> concepts.</p>

  <h3>Class template <code>transition</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "transition parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>Event</code></td>

      <td>A model of the <a href="#Event">Event</a> concept or
      the class <code><a href="#Classevent_base">event_base</a></code></td>

      <td>The event triggering the transition. If <code><a href=
      "#Classevent_base">event_base</a></code> is specified, the transition
      is triggered by all models of the <a href="#Event">Event</a>
      concept</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>Destination</code></td>

      <td>A model of the <a href="#SimpleState">SimpleState</a>
      or <a href="#State">State</a> concepts, any of their public base types or an instantiation of the
      <code><a href=
      "#ClassTemplateshallow_history">shallow_history</a></code> or
      <code><a href="#ClassTemplatedeep_history">deep_history</a></code>
      class templates. The source state (the state for which this transition
      is defined) and <code>Destination</code> must have a common direct or
      indirect context</td>

      <td>The destination state to make a transition to</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>TransitionContext</code></td>

      <td>A common context of the source and
      <code>Destination</code> state</td>

      <td>The state of which the transition action is a
      member</td>

      <td><i><code>unspecified</code></i></td>
    </tr>

    <tr>
      <td><code>pTransitionAction</code></td>

      <td>A pointer to a member function of
      <code>TransitionContext</code>. The member function must accept a
      <code>const Event &amp;</code> parameter and return
      <code>void</code></td>

      <td>The transition action that is executed during the
      transition. By default no transition action is executed</td>

      <td><i><code>unspecified</code></i></td>
    </tr>
  </table>

  <h3>Class template <code>transition</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class Event,
    class Destination,
    class TransitionContext = <i>unspecified</i>,
    void ( TransitionContext::*pTransitionAction )(
      const Event &amp; ) = <i>unspecified</i> &gt;
  class transition
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h3>Class template <code>transition</code> semantics</h3>

  <p>When executed, one of the following calls to a member function of the
  state for which the reaction was defined is made:</p>

  <ul>
    <li><code><a href="#transit1">transit&lt; Destination &gt;()</a></code>,
    if no transition action was specified</li>

    <li><code><a href="#transit2">transit&lt; Destination &gt;(
    pTransitionAction, <i>currentEvent</i> )</a></code>, if a transition
    action was specified</li>
  </ul>

  <h1>Header &lt;boost/statechart/<a name="in_state_reaction.hpp" id=
  "in_state_reaction.hpp">in_state_reaction.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatein_state_reaction" id=
  "ClassTemplatein_state_reaction">Class template
  <code>in_state_reaction</code></a></h2>

  <p>This class template is used to specify an in-state reaction.
  Instantiations of this template can appear in the <code>reactions</code>
  member <code>typedef</code> in models of the <a href=
  "#SimpleState">SimpleState</a> and <a href="#State">State</a> concepts.</p>

  <h3>Class template <code>in_state_reaction</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "in_state_reaction parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>

      <td><b>Default</b></td>
    </tr>

    <tr>
      <td><code>Event</code></td>

      <td>A model of the <a href="#Event">Event</a> concept or
      the class <code><a href="#Classevent_base">event_base</a></code></td>

      <td>The event triggering the in-state reaction. If
      <code><a href="#Classevent_base">event_base</a></code> is specified,
      the in-state reaction is triggered by all models of the <a href=
      "#Event">Event</a> concept</td>

      <td>&nbsp;</td>
    </tr>

    <tr>
      <td><code>ReactionContext</code></td>

      <td>Either the state defining the in-state reaction itself, one of its direct or indirect contexts 
          or any of their public base types</td>

      <td>The state of which the action is a member</td>

      <td><i><code>unspecified</code></i></td>
    </tr>

    <tr>
      <td><code>pAction</code></td>

      <td>A pointer to a member function of
      <code>ReactionContext</code>. The member function must accept a
      <code>const Event &amp;</code> parameter and return
      <code>void</code></td>

      <td>The action that is executed during the in-state
      reaction</td>

      <td><i><code>unspecified</code></i></td>
    </tr>
  </table>

  <h3>Class template <code>in_state_reaction</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt;
    class Event,
    class ReactionContext = <i>unspecified</i>,
    void ( ReactionContext::*pAction )(
      const Event &amp; ) = <i>unspecified</i> &gt;
  class in_state_reaction
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h3>Class template <code>in_state_reaction</code> semantics</h3>

  <p>When executed then the following happens:</p>
  <ol>
    <li>If an action was specified, <code>pAction</code> is called, passing
    the triggering event as the only argument</li>
    <li>A call is made to the <code><a href="#discard_event">discard_event</a>
    </code> member function of the state for which the reaction was defined
    </li>
  </ol>

  <h1>Header &lt;boost/statechart/<a name="termination.hpp" id=
  "termination.hpp">termination.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatetermination" id="ClassTemplatetermination">Class
  template <code>termination</code></a></h2>

  <p>This class template is used to specify a termination reaction.
  Instantiations of this template can appear in the <code>reactions</code>
  member <code>typedef</code> in models of the <a href=
  "#SimpleState">SimpleState</a> and <a href="#State">State</a> concepts.</p>

  <h3>Class template <code>termination</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "termination parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>
    </tr>

    <tr>
      <td><code>Event</code></td>

      <td>A model of the <a href="#Event">Event</a> concept or
      the class <code><a href="#Classevent_base">event_base</a></code></td>

      <td>The event triggering the termination. If <code><a href=
      "#Classevent_base">event_base</a></code> is specified, the termination
      is triggered by all models of the <a href="#Event">Event</a>
      concept</td>
    </tr>
  </table>

  <h3>Class template <code>termination</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class Event &gt;
  class termination
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h3>Class template <code>termination</code> semantics</h3>

  <p>When executed, a call is made to the <code><a href=
  "#simple_state::terminate">terminate</a></code> member function of the
  state for which the reaction was defined.</p>

  <h1>Header &lt;boost/statechart/<a name="deferral.hpp" id=
  "deferral.hpp">deferral.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatedeferral" id="ClassTemplatedeferral">Class
  template <code>deferral</code></a></h2>

  <p>This class template is used to specify a deferral reaction.
  Instantiations of this template can appear in the <code>reactions</code>
  member <code>typedef</code> in models of the <a href=
  "#SimpleState">SimpleState</a> and <a href="#State">State</a> concepts.</p>

  <h3>Class template <code>deferral</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "deferral parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>
    </tr>

    <tr>
      <td><code>Event</code></td>

      <td>A model of the <a href="#Event">Event</a> concept or
      the class <code><a href="#Classevent_base">event_base</a></code></td>

      <td>The event triggering the deferral. If <code><a href=
      "#Classevent_base">event_base</a></code> is specified, the deferral is
      triggered by all models of the <a href="#Event">Event</a> concept</td>
    </tr>
  </table>

  <h3>Class template <code>deferral</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class Event &gt;
  class deferral
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h3>Class template <code>deferral</code> semantics</h3>

  <p>When executed, a call is made to the <a href=
  "#defer_event"><code>defer_event</code></a> member function of the state
  for which the reaction was defined.</p>

  <h1>Header &lt;boost/statechart/<a name="custom_reaction.hpp" id=
  "custom_reaction.hpp">custom_reaction.hpp</a>&gt;</h1>

  <h2><a name="ClassTemplatecustom_reaction" id=
  "ClassTemplatecustom_reaction">Class template
  <code>custom_reaction</code></a></h2>

  <p>This class template is used to specify a custom reaction. Instantiations
  of this template can appear in the <code>reactions</code> member
  <code>typedef</code> in models of the <a href=
  "#SimpleState">SimpleState</a> and <a href="#State">State</a> concepts.</p>

  <h3>Class template <code>custom_reaction</code> parameters</h3>

  <table border="3" cellpadding="2" width="100%" summary=
  "custom_reaction parameters">
    <tr>
      <td><b>Template parameter</b></td>

      <td><b>Requirements</b></td>

      <td><b>Semantics</b></td>
    </tr>

    <tr>
      <td><code>Event</code></td>

      <td>A model of the <a href="#Event">Event</a> concept or
      the class <code><a href="#Classevent_base">event_base</a></code></td>

      <td>The event triggering the custom reaction. If
      <code><a href="#Classevent_base">event_base</a></code> is specified,
      the custom reaction is triggered by all models of the <a href=
      "#Event">Event</a> concept</td>
    </tr>
  </table>

  <h3>Class template <code>custom_reaction</code> synopsis</h3>
  <pre>
namespace boost
{
namespace statechart
{
  template&lt; class Event &gt;
  class custom_reaction
  {
    // <i>implementation-defined</i>
  };
}
}
</pre>

  <h3>Class template <code>custom_reaction</code> semantics</h3>

  <p>When executed, a call is made to the user-supplied <code>react</code>
  member function of the state for which the reaction was defined. The
  <code>react</code> member function must have the following signature:</p>
  <pre>
<a href="#Classresult">result</a> react( const Event &amp; );
</pre>

  <p>and must call exactly one of the following reaction functions and return
  the obtained <code><a href="#Classresult">result</a></code> object:</p>
  <pre>
<a href="#Classresult">result</a> <a href=
"#discard_event">discard_event</a>();
<a href="#Classresult">result</a> <a href=
"#forward_event">forward_event</a>();
<a href="#Classresult">result</a> <a href="#defer_event">defer_event</a>();
template&lt; class DestinationState &gt;
<a href="#Classresult">result</a> <a href="#transit1">transit</a>();
template&lt;
  class DestinationState,
  class TransitionContext,
  class Event &gt;
<a href="#Classresult">result</a> <a href="#transit2">transit</a>(
  void ( TransitionContext::* )( const Event &amp; ),
  const Event &amp; );
<a href="#Classresult">result</a> <a href=
"#simple_state::terminate">terminate</a>();
</pre>

  <h1>Header &lt;boost/statechart/<a name="result.hpp" id=
  "result.hpp">result.hpp</a>&gt;</h1>

  <h2><a name="Classresult" id="Classresult">Class
  <code>result</code></a></h2>

  <p>Defines the nature of the reaction taken in a user-supplied
  <code>react</code> member function (called when a <code><a href=
  "#ClassTemplatecustom_reaction">custom_reaction</a></code> is executed).
  Objects of this type are always obtained by calling one of the reaction
  functions and must be returned from the <code>react</code> member function
  immediately.</p>
  <pre>
namespace boost
{
namespace statechart
{
  class result
  {
    public:
      <a href="#result0">result</a>( const result &amp; other );
      <a href="#resultdtor">~result</a>();

    private:
      // Result objects are not assignable
      result &amp; operator=( const result &amp; other );
  };
}
}
</pre>

  <h3>Class <code>result</code> constructor and destructor</h3>
  <pre>
<a name="result0" id="result0">result</a>( const result &amp; other );
</pre>

  <p><b>Requires</b>: <code>other</code> is <b>not</b> consumed<br>
  <b>Effects</b>: Copy-constructs a new <code>result</code> object and marks
  <code>other</code> as consumed. That is, <code>result</code> has
  destructive copy semantics</p>
  <pre>
<a name="resultdtor" id="resultdtor">~result</a>();
</pre>

  <p><b>Requires</b>: <code>this</code> is marked as consumed<br>
  <b>Effects</b>: Destructs the result object</p>
  <hr>

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  <p>Revised 06 November, 2010</p>

  <p><i>Copyright &copy; 2003-2010 <a href="contact.html">Andreas Huber
  D&ouml;nni</a></i></p>

  <p><i>Distributed under the Boost Software License, Version 1.0. (See
  accompanying file <a href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  copy at <a href=
  "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p>
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