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<div class="identifier-type">class</div><div class="header"><coroutine></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">suspend_never</span><span class="cpp cpp20" title="C++20で追加">(C++20)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">suspend_never</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">bool</span><span class="w"> </span><span class="nf">await_ready</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="nb">true</span><span class="p">;</span><span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">await_suspend</span><span class="p">(</span><span class="n"><a href="coroutine_handle.html">coroutine_handle<></a></span><span class="p">)</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">await_resume</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">noexcept</span><span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="p">};</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p>コルーチンを中断させない、トリビアルAwaitable型。</p>
<h2>メンバ関数</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>await_ready</code></td>
<td>コルーチンを常に中断しない</td>
<td>C++20</td>
</tr>
<tr>
<td><code>await_suspend</code></td>
<td>コルーチン中断時に何もしない</td>
<td>C++20</td>
</tr>
<tr>
<td><code>await_resume</code></td>
<td>コルーチン再開時に何もしない</td>
<td>C++20</td>
</tr>
</tbody>
</table>
<h2>例</h2>
<p><div class="yata" id="2c164012ca5e870a4aff2d642bbdd8983d3e92fc"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../coroutine.html"><coroutine></a></span>
<span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../utility.html"><utility></a></span>
<span class="k">struct</span><span class="w"> </span><span class="nc">task</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">promise_type</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">value_</span><span class="p">;</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">get_return_object</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">task</span><span class="p">{</span><span class="o">*</span><span class="k">this</span><span class="p">};</span><span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">initial_suspend</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::suspend_never</span></span><span class="p">{};</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">final_suspend</span><span class="p">()</span><span class="w"> </span><span class="k">noexcept</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n"><a href="suspend_always.html">std::suspend_always</a></span><span class="p">{};</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">return_value</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">value_</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span><span class="p">;</span><span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">unhandled_exception</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">terminate</span><span class="p">();</span><span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">};</span>
<span class="w"> </span><span class="k">using</span><span class="w"> </span><span class="n">coro_handle</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="coroutine_handle.html">std::coroutine_handle</a></span><span class="o"><</span><span class="n">promise_type</span><span class="o">></span><span class="p">;</span>
<span class="w"> </span><span class="o">~</span><span class="n">task</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">coro_</span><span class="p">)</span>
<span class="w"> </span><span class="n">coro_</span><span class="p">.</span><span class="n">destroy</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">task</span><span class="p">(</span><span class="n">task</span><span class="w"> </span><span class="k">const</span><span class="o">&</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">delete</span><span class="p">;</span>
<span class="w"> </span><span class="n">task</span><span class="p">(</span><span class="n">task</span><span class="o">&&</span><span class="w"> </span><span class="n">rhs</span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">coro_</span><span class="p">(</span><span class="n"><a href="../utility/exchange.html">std::exchange</a></span><span class="p">(</span><span class="n">rhs</span><span class="p">.</span><span class="n">coro_</span><span class="p">,</span><span class="w"> </span><span class="k">nullptr</span><span class="p">))</span><span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">get</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">coro_</span><span class="p">.</span><span class="n"><a href="coroutine_handle/done.html">done()</a></span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">coro_</span><span class="p">.</span><span class="n"><a href="coroutine_handle/resume.html">resume()</a></span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">coro_</span><span class="p">.</span><span class="n"><a href="coroutine_handle/promise.html">promise()</a></span><span class="p">.</span><span class="n">value_</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="k">private</span><span class="o">:</span>
<span class="w"> </span><span class="k">explicit</span><span class="w"> </span><span class="n">task</span><span class="p">(</span><span class="n">promise_type</span><span class="o">&</span><span class="w"> </span><span class="n">p</span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">coro_</span><span class="p">(</span><span class="n">coro_handle</span><span class="o">::</span><span class="n"><a href="coroutine_handle/from_promise.html">from_promise</a></span><span class="p">(</span><span class="n">p</span><span class="p">))</span><span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="n">coro_handle</span><span class="w"> </span><span class="n">coro_</span><span class="p">;</span>
<span class="p">};</span>
<span class="n">task</span><span class="w"> </span><span class="nf">f</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"coroutine"</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="k">co_return</span><span class="w"> </span><span class="mi">42</span><span class="p">;</span>
<span class="p">}</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"main"</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="p">.</span><span class="n">get</span><span class="p">();</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"result="</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code>coroutine
main
result=42
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++20</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: ??</li>
<li><a href="../../implementation.html#gcc">GCC</a>: 11.1 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: ??</li>
</ul>
<h2>関連項目</h2>
<ul>
<li><a href="../../lang/cpp20/coroutines.html">C++20 コルーチン</a></li>
<li><code><a href="suspend_always.html">suspend_always</a></code></li>
</ul></div>
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