330 lines
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330 lines
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<h1 class="title">Factorial States Example</h1>
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<span class="subtitle"></span>
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<!-- $$$statemachine/factorial-description -->
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<div class="descr"> <a name="details"></a>
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<p>Files:</p>
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<ul>
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<li><a href="statemachine-factorial-main-cpp.html">statemachine/factorial/main.cpp</a></li>
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<li><a href="statemachine-factorial-factorial-pro.html">statemachine/factorial/factorial.pro</a></li>
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</ul>
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<p>The Factorial States example shows how to use <a href="statemachine-api.html">The State Machine Framework</a> to calculate the factorial of an integer.<p>The statechart for calculating the factorial looks as follows:</p>
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<p class="centerAlign"><img src="images/factorial-example.png" alt="" /></p><p>In other words, the state machine calculates the factorial of 6 and prints the result.</p>
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<pre class="cpp"> <span class="keyword">class</span> Factorial : <span class="keyword">public</span> <span class="type"><a href="qobject.html">QObject</a></span>
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{
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Q_OBJECT
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Q_PROPERTY(<span class="type">int</span> x READ x WRITE setX)
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Q_PROPERTY(<span class="type">int</span> fac READ fac WRITE setFac)
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<span class="keyword">public</span>:
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Factorial(<span class="type"><a href="qobject.html">QObject</a></span> <span class="operator">*</span>parent <span class="operator">=</span> <span class="number">0</span>)
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: <span class="type"><a href="qobject.html">QObject</a></span>(parent)<span class="operator">,</span> m_x(<span class="operator">-</span><span class="number">1</span>)<span class="operator">,</span> m_fac(<span class="number">1</span>)
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{
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}
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<span class="type">int</span> x() <span class="keyword">const</span>
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{
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<span class="keyword">return</span> m_x;
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}
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<span class="type">void</span> setX(<span class="type">int</span> x)
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{
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<span class="keyword">if</span> (x <span class="operator">=</span><span class="operator">=</span> m_x)
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<span class="keyword">return</span>;
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m_x <span class="operator">=</span> x;
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<span class="keyword">emit</span> xChanged(x);
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}
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<span class="type">int</span> fac() <span class="keyword">const</span>
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{
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<span class="keyword">return</span> m_fac;
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}
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<span class="type">void</span> setFac(<span class="type">int</span> fac)
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{
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m_fac <span class="operator">=</span> fac;
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}
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Q_SIGNALS:
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<span class="type">void</span> xChanged(<span class="type">int</span> value);
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<span class="keyword">private</span>:
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<span class="type">int</span> m_x;
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<span class="type">int</span> m_fac;
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};</pre>
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<p>The Factorial class is used to hold the data of the computation, <tt>x</tt> and <tt>fac</tt>. It also provides a signal that's emitted whenever the value of <tt>x</tt> changes.</p>
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<pre class="cpp"> <span class="keyword">class</span> FactorialLoopTransition : <span class="keyword">public</span> <span class="type"><a href="qsignaltransition.html">QSignalTransition</a></span>
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{
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<span class="keyword">public</span>:
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FactorialLoopTransition(Factorial <span class="operator">*</span>fact)
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: <span class="type"><a href="qsignaltransition.html">QSignalTransition</a></span>(fact<span class="operator">,</span> SIGNAL(xChanged(<span class="type">int</span>)))<span class="operator">,</span> m_fact(fact)
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{}
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<span class="keyword">virtual</span> <span class="type">bool</span> eventTest(<span class="type"><a href="qevent.html">QEvent</a></span> <span class="operator">*</span>e)
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{
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<span class="keyword">if</span> (<span class="operator">!</span><span class="type"><a href="qsignaltransition.html">QSignalTransition</a></span><span class="operator">::</span>eventTest(e))
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<span class="keyword">return</span> <span class="keyword">false</span>;
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<span class="type"><a href="qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent <span class="operator">*</span>se <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent<span class="operator">*</span><span class="operator">></span>(e);
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<span class="keyword">return</span> se<span class="operator">-</span><span class="operator">></span>arguments()<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toInt() <span class="operator">></span> <span class="number">1</span>;
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}
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<span class="keyword">virtual</span> <span class="type">void</span> onTransition(<span class="type"><a href="qevent.html">QEvent</a></span> <span class="operator">*</span>e)
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{
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<span class="type"><a href="qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent <span class="operator">*</span>se <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent<span class="operator">*</span><span class="operator">></span>(e);
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<span class="type">int</span> x <span class="operator">=</span> se<span class="operator">-</span><span class="operator">></span>arguments()<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toInt();
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<span class="type">int</span> fac <span class="operator">=</span> m_fact<span class="operator">-</span><span class="operator">></span>property(<span class="string">"fac"</span>)<span class="operator">.</span>toInt();
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m_fact<span class="operator">-</span><span class="operator">></span>setProperty(<span class="string">"fac"</span><span class="operator">,</span> x <span class="operator">*</span> fac);
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m_fact<span class="operator">-</span><span class="operator">></span>setProperty(<span class="string">"x"</span><span class="operator">,</span> x <span class="operator">-</span> <span class="number">1</span>);
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}
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<span class="keyword">private</span>:
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Factorial <span class="operator">*</span>m_fact;
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};</pre>
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<p>The FactorialLoopTransition class implements the guard (<tt>x</tt> > 1) and calculations (<tt>fac</tt> = <tt>x</tt> * <tt>fac</tt>; <tt>x</tt> = <tt>x</tt> - 1) of the factorial loop.</p>
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<pre class="cpp"> <span class="keyword">class</span> FactorialDoneTransition : <span class="keyword">public</span> <span class="type"><a href="qsignaltransition.html">QSignalTransition</a></span>
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{
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<span class="keyword">public</span>:
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FactorialDoneTransition(Factorial <span class="operator">*</span>fact)
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: <span class="type"><a href="qsignaltransition.html">QSignalTransition</a></span>(fact<span class="operator">,</span> SIGNAL(xChanged(<span class="type">int</span>)))<span class="operator">,</span> m_fact(fact)
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{}
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<span class="keyword">virtual</span> <span class="type">bool</span> eventTest(<span class="type"><a href="qevent.html">QEvent</a></span> <span class="operator">*</span>e)
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{
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<span class="keyword">if</span> (<span class="operator">!</span><span class="type"><a href="qsignaltransition.html">QSignalTransition</a></span><span class="operator">::</span>eventTest(e))
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<span class="keyword">return</span> <span class="keyword">false</span>;
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<span class="type"><a href="qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent <span class="operator">*</span>se <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent<span class="operator">*</span><span class="operator">></span>(e);
|
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<span class="keyword">return</span> se<span class="operator">-</span><span class="operator">></span>arguments()<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toInt() <span class="operator"><</span><span class="operator">=</span> <span class="number">1</span>;
|
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}
|
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<span class="keyword">virtual</span> <span class="type">void</span> onTransition(<span class="type"><a href="qevent.html">QEvent</a></span> <span class="operator">*</span>)
|
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{
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fprintf(stdout<span class="operator">,</span> <span class="string">"%d\n"</span><span class="operator">,</span> m_fact<span class="operator">-</span><span class="operator">></span>property(<span class="string">"fac"</span>)<span class="operator">.</span>toInt());
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}
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<span class="keyword">private</span>:
|
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Factorial <span class="operator">*</span>m_fact;
|
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};</pre>
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<p>The FactorialDoneTransition class implements the guard (<tt>x</tt> <= 1) that terminates the factorial computation. It also prints the final result to standard output.</p>
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<pre class="cpp"> <span class="type">int</span> main(<span class="type">int</span> argc<span class="operator">,</span> <span class="type">char</span> <span class="operator">*</span><span class="operator">*</span>argv)
|
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{
|
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<span class="type"><a href="qcoreapplication.html">QCoreApplication</a></span> app(argc<span class="operator">,</span> argv);
|
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Factorial factorial;
|
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<span class="type"><a href="qstatemachine.html">QStateMachine</a></span> machine;</pre>
|
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<p>The application's main() function first creates the application object, a Factorial object and a state machine.</p>
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<pre class="cpp"> <span class="type"><a href="qstate.html">QState</a></span> <span class="operator">*</span>compute <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qstate.html">QState</a></span>(<span class="operator">&</span>machine);
|
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compute<span class="operator">-</span><span class="operator">></span>assignProperty(<span class="operator">&</span>factorial<span class="operator">,</span> <span class="string">"fac"</span><span class="operator">,</span> <span class="number">1</span>);
|
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compute<span class="operator">-</span><span class="operator">></span>assignProperty(<span class="operator">&</span>factorial<span class="operator">,</span> <span class="string">"x"</span><span class="operator">,</span> <span class="number">6</span>);
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compute<span class="operator">-</span><span class="operator">></span>addTransition(<span class="keyword">new</span> FactorialLoopTransition(<span class="operator">&</span>factorial));</pre>
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<p>The <tt>compute</tt> state is created, and the initial values of <tt>x</tt> and <tt>fac</tt> are defined. A FactorialLoopTransition object is created and added to the state.</p>
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<pre class="cpp"> <span class="type"><a href="qfinalstate.html">QFinalState</a></span> <span class="operator">*</span>done <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qfinalstate.html">QFinalState</a></span>(<span class="operator">&</span>machine);
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FactorialDoneTransition <span class="operator">*</span>doneTransition <span class="operator">=</span> <span class="keyword">new</span> FactorialDoneTransition(<span class="operator">&</span>factorial);
|
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doneTransition<span class="operator">-</span><span class="operator">></span>setTargetState(done);
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compute<span class="operator">-</span><span class="operator">></span>addTransition(doneTransition);</pre>
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<p>A final state, <tt>done</tt>, is created, and a FactorialDoneTransition object is created with <tt>done</tt> as its target state. The transition is then added to the <tt>compute</tt> state.</p>
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<pre class="cpp"> machine<span class="operator">.</span>setInitialState(compute);
|
|
<span class="type"><a href="qobject.html">QObject</a></span><span class="operator">::</span>connect(<span class="operator">&</span>machine<span class="operator">,</span> SIGNAL(finished())<span class="operator">,</span> <span class="operator">&</span>app<span class="operator">,</span> SLOT(quit()));
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machine<span class="operator">.</span>start();
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|
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<span class="keyword">return</span> app<span class="operator">.</span>exec();
|
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}</pre>
|
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<p>The machine's initial state is set to be the <tt>compute</tt> state. We connect the <a href="qstate.html#finished">QStateMachine::finished</a>() signal to the <a href="qcoreapplication.html#quit">QCoreApplication::quit</a>() slot, so the application will quit when the state machine's work is done. Finally, the state machine is started, and the application's event loop is entered.</p>
|
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</div>
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<!-- @@@statemachine/factorial -->
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