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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="coroutine.coroutine.symmetric"></a><a class="link" href="symmetric.html" title="Symmetric coroutine">Symmetric coroutine</a> |
| </h3></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="symmetric/symmetric_coro.html">Class |
| <code class="computeroutput"><span class="identifier">symmetric_coroutine</span><span class="special"><>::</span><span class="identifier">call_type</span></code></a></span></dt> |
| <dt><span class="section"><a href="symmetric/yield_coro.html">Class <code class="computeroutput"><span class="identifier">symmetric_coroutine</span><span class="special"><>::</span><span class="identifier">yield_type</span></code></a></span></dt> |
| </dl></div> |
| <p> |
| In contrast to asymmetric coroutines, where the relationship between caller |
| and callee is fixed, symmetric coroutines are able to transfer execution |
| control to any other (symmetric) coroutine. E.g. a symmetric coroutine is |
| not required to return to its direct caller. |
| </p> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h0"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric._emphasis_symmetric_coroutine_lt__gt___call_type__emphasis_"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric._emphasis_symmetric_coroutine_lt__gt___call_type__emphasis_"><span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span></a> |
| </h5> |
| <p> |
| <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> starts a symmetric |
| coroutine and transfers its parameter to its <span class="emphasis"><em>coroutine-function</em></span>. |
| The template parameter defines the transferred parameter type. The constructor |
| of <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> takes a function |
| (<span class="emphasis"><em>coroutine-function</em></span>) accepting a reference to a <span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span> |
| as argument. Instantiating a <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| does not pass the control of execution to <span class="emphasis"><em>coroutine-function</em></span> |
| - instead the first call of <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator()</em></span> |
| synthesizes a <span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span> |
| and passes it as reference to <span class="emphasis"><em>coroutine-function</em></span>. |
| </p> |
| <p> |
| The <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> interface |
| does not contain a <span class="emphasis"><em>get()</em></span>-function: you can not retrieve |
| values from another execution context with this kind of coroutine object. |
| </p> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h1"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric._emphasis_symmetric_coroutine_lt__gt___yield_type__emphasis_"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric._emphasis_symmetric_coroutine_lt__gt___yield_type__emphasis_"><span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span></a> |
| </h5> |
| <p> |
| <span class="emphasis"><em>symmetric_coroutine<>::yield_type::operator()</em></span> |
| is used to transfer data and execution control to another context by calling |
| <span class="emphasis"><em>symmetric_coroutine<>::yield_type::operator()</em></span> |
| with another <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| as first argument. Alternatively, you may transfer control back to the code |
| that called <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator()</em></span> |
| by calling <span class="emphasis"><em>symmetric_coroutine<>::yield_type::operator()</em></span> |
| without a <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> argument. |
| </p> |
| <p> |
| The class has only one template parameter defining the transferred parameter |
| type. Data transferred to the coroutine are accessed through <span class="emphasis"><em>symmetric_coroutine<>::yield_type::get()</em></span>. |
| </p> |
| <div class="important"><table border="0" summary="Important"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> |
| <th align="left">Important</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| <span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span> can only be |
| created by the framework. |
| </p></td></tr> |
| </table></div> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">merge</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">>&</span> <span class="identifier">a</span><span class="special">,</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">>&</span> <span class="identifier">b</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">c</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">idx_a</span><span class="special">=</span><span class="number">0</span><span class="special">,</span><span class="identifier">idx_b</span><span class="special">=</span><span class="number">0</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">call_type</span><span class="special">*</span> <span class="identifier">other_a</span><span class="special">=</span><span class="number">0</span><span class="special">,*</span> <span class="identifier">other_b</span><span class="special">=</span><span class="number">0</span><span class="special">;</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">call_type</span> <span class="identifier">coro_a</span><span class="special">(</span> |
| <span class="special">[&](</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">yield_type</span><span class="special">&</span> <span class="identifier">yield</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">while</span><span class="special">(</span><span class="identifier">idx_a</span><span class="special"><</span><span class="identifier">a</span><span class="special">.</span><span class="identifier">size</span><span class="special">())</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span><span class="special">(</span><span class="identifier">b</span><span class="special">[</span><span class="identifier">idx_b</span><span class="special">]<</span><span class="identifier">a</span><span class="special">[</span><span class="identifier">idx_a</span><span class="special">])</span> <span class="comment">// test if element in array b is less than in array a</span> |
| <span class="identifier">yield</span><span class="special">(*</span><span class="identifier">other_b</span><span class="special">);</span> <span class="comment">// yield to coroutine coro_b</span> |
| <span class="identifier">c</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">a</span><span class="special">[</span><span class="identifier">idx_a</span><span class="special">++]);</span> <span class="comment">// add element to final array</span> |
| <span class="special">}</span> |
| <span class="comment">// add remaining elements of array b</span> |
| <span class="keyword">while</span> <span class="special">(</span> <span class="identifier">idx_b</span> <span class="special"><</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">size</span><span class="special">())</span> |
| <span class="identifier">c</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span> <span class="identifier">b</span><span class="special">[</span><span class="identifier">idx_b</span><span class="special">++]);</span> |
| <span class="special">});</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">call_type</span> <span class="identifier">coro_b</span><span class="special">(</span> |
| <span class="special">[&](</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">yield_type</span><span class="special">&</span> <span class="identifier">yield</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">while</span><span class="special">(</span><span class="identifier">idx_b</span><span class="special"><</span><span class="identifier">b</span><span class="special">.</span><span class="identifier">size</span><span class="special">())</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">a</span><span class="special">[</span><span class="identifier">idx_a</span><span class="special">]<</span><span class="identifier">b</span><span class="special">[</span><span class="identifier">idx_b</span><span class="special">])</span> <span class="comment">// test if element in array a is less than in array b</span> |
| <span class="identifier">yield</span><span class="special">(*</span><span class="identifier">other_a</span><span class="special">);</span> <span class="comment">// yield to coroutine coro_a</span> |
| <span class="identifier">c</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">b</span><span class="special">[</span><span class="identifier">idx_b</span><span class="special">++]);</span> <span class="comment">// add element to final array</span> |
| <span class="special">}</span> |
| <span class="comment">// add remaining elements of array a</span> |
| <span class="keyword">while</span> <span class="special">(</span> <span class="identifier">idx_a</span> <span class="special"><</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">size</span><span class="special">())</span> |
| <span class="identifier">c</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span> <span class="identifier">a</span><span class="special">[</span><span class="identifier">idx_a</span><span class="special">++]);</span> |
| <span class="special">});</span> |
| |
| |
| <span class="identifier">other_a</span> <span class="special">=</span> <span class="special">&</span> <span class="identifier">coro_a</span><span class="special">;</span> |
| <span class="identifier">other_b</span> <span class="special">=</span> <span class="special">&</span> <span class="identifier">coro_b</span><span class="special">;</span> |
| |
| <span class="identifier">coro_a</span><span class="special">();</span> <span class="comment">// enter coroutine-fn of coro_a</span> |
| |
| <span class="keyword">return</span> <span class="identifier">c</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span> <span class="keyword">int</span> <span class="special">></span> <span class="identifier">a</span> <span class="special">=</span> <span class="special">{</span><span class="number">1</span><span class="special">,</span><span class="number">5</span><span class="special">,</span><span class="number">6</span><span class="special">,</span><span class="number">10</span><span class="special">};</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span> <span class="keyword">int</span> <span class="special">></span> <span class="identifier">b</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span><span class="number">4</span><span class="special">,</span><span class="number">7</span><span class="special">,</span><span class="number">8</span><span class="special">,</span><span class="number">9</span><span class="special">,</span><span class="number">13</span><span class="special">};</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span> <span class="keyword">int</span> <span class="special">></span> <span class="identifier">c</span> <span class="special">=</span> <span class="identifier">merge</span><span class="special">(</span><span class="identifier">a</span><span class="special">,</span><span class="identifier">b</span><span class="special">);</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">a</span><span class="special">);</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">b</span><span class="special">);</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">c</span><span class="special">);</span> |
| |
| <span class="identifier">output</span><span class="special">:</span> |
| <span class="identifier">a</span> <span class="special">:</span> <span class="number">1</span> <span class="number">5</span> <span class="number">6</span> <span class="number">10</span> |
| <span class="identifier">b</span> <span class="special">:</span> <span class="number">2</span> <span class="number">4</span> <span class="number">7</span> <span class="number">8</span> <span class="number">9</span> <span class="number">13</span> |
| <span class="identifier">c</span> <span class="special">:</span> <span class="number">1</span> <span class="number">2</span> <span class="number">4</span> <span class="number">5</span> <span class="number">6</span> <span class="number">7</span> <span class="number">8</span> <span class="number">9</span> <span class="number">10</span> <span class="number">13</span> |
| </pre> |
| <p> |
| In this example two <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| are created in the main execution context accepting a lambda function (== |
| <span class="emphasis"><em>coroutine-function</em></span>) which merges elements of two sorted |
| arrays into a third array. <code class="computeroutput"><span class="identifier">coro_a</span><span class="special">()</span></code> enters the <span class="emphasis"><em>coroutine-function</em></span> |
| of <code class="computeroutput"><span class="identifier">coro_a</span></code> cycling through |
| the array and testing if the actual element in the other array is less than |
| the element in the local one. If so, the coroutine yields to the other coroutine |
| <code class="computeroutput"><span class="identifier">coro_b</span></code> using <code class="computeroutput"><span class="identifier">yield</span><span class="special">(*</span><span class="identifier">other_b</span><span class="special">)</span></code>. |
| If the current element of the local array is less than the element of the |
| other array, it is put to the third array. Because the coroutine jumps back |
| to <code class="computeroutput"><span class="identifier">coro_a</span><span class="special">()</span></code> |
| (returning from this method) after leaving the <span class="emphasis"><em>coroutine-function</em></span>, |
| the elements of the other array will appended at the end of the third array |
| if all element of the local array are processed. |
| </p> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h2"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric.coroutine_function"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric.coroutine_function">coroutine-function</a> |
| </h5> |
| <p> |
| The <span class="emphasis"><em>coroutine-function</em></span> returns <span class="emphasis"><em>void</em></span> |
| and takes <span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span>, providing |
| coroutine functionality inside the <span class="emphasis"><em>coroutine-function</em></span>, |
| as argument. Using this instance is the only way to transfer data and execution |
| control. <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> does |
| not enter the <span class="emphasis"><em>coroutine-function</em></span> at <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| construction but at the first invocation of <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator()</em></span>. |
| </p> |
| <p> |
| Unless the template parameter is <code class="computeroutput"><span class="keyword">void</span></code>, |
| the <span class="emphasis"><em>coroutine-function</em></span> of a <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| can assume that (a) upon initial entry and (b) after every <span class="emphasis"><em>symmetric_coroutine<>::yield_type::operator()</em></span> |
| call, its <span class="emphasis"><em>symmetric_coroutine<>::yield_type::get()</em></span> |
| has a new value available. |
| </p> |
| <p> |
| However, if the template parameter is a move-only type, <span class="emphasis"><em>symmetric_coroutine<>::yield_type::get()</em></span> |
| may only be called once before the next <span class="emphasis"><em>symmetric_coroutine<>::yield_type::operator()</em></span> |
| call. |
| </p> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h3"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric.passing_data_from_main_context_to_a_symmetric_coroutine"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric.passing_data_from_main_context_to_a_symmetric_coroutine">passing |
| data from main-context to a symmetric-coroutine</a> |
| </h5> |
| <p> |
| In order to transfer data to a <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| from the main-context the framework synthesizes a <span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span> |
| associated with the <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> |
| instance. The synthesized <span class="emphasis"><em>symmetric_coroutine<>::yield_type</em></span> |
| is passed as argument to <span class="emphasis"><em>coroutine-function</em></span>. The main-context |
| must call <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator()</em></span> |
| in order to transfer each data value into the <span class="emphasis"><em>coroutine-function</em></span>. |
| Access to the transferred data value is given by <span class="emphasis"><em>symmetric_coroutine<>::yield_type::get()</em></span>. |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">call_type</span> <span class="identifier">coro</span><span class="special">(</span> <span class="comment">// constructor does NOT enter coroutine-function</span> |
| <span class="special">[&](</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">yield_type</span><span class="special">&</span> <span class="identifier">yield</span><span class="special">){</span> |
| <span class="keyword">for</span> <span class="special">(;;)</span> <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">yield</span><span class="special">.</span><span class="identifier">get</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" "</span><span class="special">;</span> |
| <span class="identifier">yield</span><span class="special">();</span> <span class="comment">// jump back to starting context</span> |
| <span class="special">}</span> |
| <span class="special">});</span> |
| |
| <span class="identifier">coro</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// transfer {1} to coroutine-function</span> |
| <span class="identifier">coro</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="comment">// transfer {2} to coroutine-function</span> |
| <span class="identifier">coro</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// transfer {3} to coroutine-function</span> |
| <span class="identifier">coro</span><span class="special">(</span><span class="number">4</span><span class="special">);</span> <span class="comment">// transfer {4} to coroutine-function</span> |
| <span class="identifier">coro</span><span class="special">(</span><span class="number">5</span><span class="special">);</span> <span class="comment">// transfer {5} to coroutine-function</span> |
| </pre> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h4"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric.exceptions"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric.exceptions">exceptions</a> |
| </h5> |
| <p> |
| An uncaught exception inside a <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span>'s |
| <span class="emphasis"><em>coroutine-function</em></span> will call <span class="emphasis"><em>std::terminate()</em></span>. |
| </p> |
| <div class="important"><table border="0" summary="Important"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> |
| <th align="left">Important</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| Code executed by coroutine must not prevent the propagation of the <span class="emphasis"><em>detail::forced_unwind</em></span> |
| exception. Absorbing that exception will cause stack unwinding to fail. |
| Thus, any code that catches all exceptions must re-throw any pending <span class="emphasis"><em>detail::forced_unwind</em></span> |
| exception. |
| </p></td></tr> |
| </table></div> |
| <pre class="programlisting"><span class="keyword">try</span> <span class="special">{</span> |
| <span class="comment">// code that might throw</span> |
| <span class="special">}</span> <span class="keyword">catch</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">forced_unwind</span><span class="special">&)</span> <span class="special">{</span> |
| <span class="keyword">throw</span><span class="special">;</span> |
| <span class="special">}</span> <span class="keyword">catch</span><span class="special">(...)</span> <span class="special">{</span> |
| <span class="comment">// possibly not re-throw pending exception</span> |
| <span class="special">}</span> |
| </pre> |
| <div class="important"><table border="0" summary="Important"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> |
| <th align="left">Important</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| Do not jump from inside a catch block and than re-throw the exception in |
| another execution context. |
| </p></td></tr> |
| </table></div> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h5"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric.stack_unwinding"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric.stack_unwinding">Stack |
| unwinding</a> |
| </h5> |
| <p> |
| Sometimes it is necessary to unwind the stack of an unfinished coroutine |
| to destroy local stack variables so they can release allocated resources |
| (RAII pattern). The <code class="computeroutput"><span class="identifier">attributes</span></code> |
| argument of the coroutine constructor indicates whether the destructor should |
| unwind the stack (stack is unwound by default). |
| </p> |
| <p> |
| Stack unwinding assumes the following preconditions: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| The coroutine is not <span class="emphasis"><em>not-a-coroutine</em></span> |
| </li> |
| <li class="listitem"> |
| The coroutine is not complete |
| </li> |
| <li class="listitem"> |
| The coroutine is not running |
| </li> |
| <li class="listitem"> |
| The coroutine owns a stack |
| </li> |
| </ul></div> |
| <p> |
| After unwinding, a <span class="emphasis"><em>coroutine</em></span> is complete. |
| </p> |
| <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> |
| <span class="identifier">X</span><span class="special">(){</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"><<</span><span class="string">"X()"</span><span class="special"><<</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="special">~</span><span class="identifier">X</span><span class="special">(){</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"><<</span><span class="string">"~X()"</span><span class="special"><<</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">int</span><span class="special">>::</span><span class="identifier">call_type</span> <span class="identifier">other_coro</span><span class="special">(...);</span> |
| |
| <span class="special">{</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">call_type</span> <span class="identifier">coro</span><span class="special">(</span> |
| <span class="special">[&](</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">coroutines</span><span class="special">::</span><span class="identifier">symmetric_coroutine</span><span class="special"><</span><span class="keyword">void</span><span class="special">>::</span><span class="identifier">yield_type</span><span class="special">&</span> <span class="identifier">yield</span><span class="special">){</span> |
| <span class="identifier">X</span> <span class="identifier">x</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"><<</span><span class="string">"fn()"</span><span class="special"><<</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="comment">// transfer execution control to other coroutine</span> |
| <span class="identifier">yield</span><span class="special">(</span> <span class="identifier">other_coro</span><span class="special">,</span> <span class="number">7</span><span class="special">);</span> |
| <span class="special">});</span> |
| |
| <span class="identifier">coro</span><span class="special">();</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"><<</span><span class="string">"coro is complete: "</span><span class="special"><<</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">boolalpha</span><span class="special"><<!</span><span class="identifier">coro</span><span class="special"><<</span><span class="string">"\n"</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">output</span><span class="special">:</span> |
| <span class="identifier">X</span><span class="special">()</span> |
| <span class="identifier">fn</span><span class="special">()</span> |
| <span class="identifier">coro</span> <span class="identifier">is</span> <span class="identifier">complete</span><span class="special">:</span> <span class="keyword">false</span> |
| <span class="special">~</span><span class="identifier">X</span><span class="special">()</span> |
| </pre> |
| <h5> |
| <a name="coroutine.coroutine.symmetric.h6"></a> |
| <span class="phrase"><a name="coroutine.coroutine.symmetric.exit_a__emphasis_coroutine_function__emphasis_"></a></span><a class="link" href="symmetric.html#coroutine.coroutine.symmetric.exit_a__emphasis_coroutine_function__emphasis_">Exit |
| a <span class="emphasis"><em>coroutine-function</em></span></a> |
| </h5> |
| <p> |
| <span class="emphasis"><em>coroutine-function</em></span> is exited with a simple return statement. |
| This jumps back to the calling <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator()</em></span> |
| at the start of symmetric coroutine chain. That is, symmetric coroutines |
| do not have a strong, fixed relationship to the caller as do asymmetric coroutines. |
| The <span class="emphasis"><em>symmetric_coroutine<>::call_type</em></span> becomes complete, |
| e.g. <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator bool</em></span> |
| will return <code class="computeroutput"><span class="keyword">false</span></code>. |
| </p> |
| <div class="important"><table border="0" summary="Important"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> |
| <th align="left">Important</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| After returning from <span class="emphasis"><em>coroutine-function</em></span> the <span class="emphasis"><em>coroutine</em></span> |
| is complete (can not be resumed with <span class="emphasis"><em>symmetric_coroutine<>::call_type::operator()</em></span>). |
| </p></td></tr> |
| </table></div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2009 Oliver Kowalke<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
| </tr></table> |
| <hr> |
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