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<div class="identifier-type">customization point object</div><div class="header"><execution></div><h1 itemprop="name"><span class="namespace" title="namespace std::execution">std::execution::</span><span class="token">on</span><span class="cpp cpp26" title="C++26で追加">(C++26)</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="o">::</span><span class="nn">execution</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">on_t</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n"><i>unspecified</i></span><span class="w"> </span><span class="p">};</span>
<span class="w"> </span><span class="kr">inline</span><span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="n">on_t</span><span class="w"> </span><span class="n">on</span><span class="p">{};</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code>on</code>は、2種類の呼び出し形式をサポートするSenderアダプタである。</p>
<ul>
<li><code>on(sch, sndr)</code> : <a href="sender.html">Sender</a><code>sndr</code>を<a href="scheduler.html">Scheduler</a><code>sch</code>に関連付けられた実行リソースに属する実行エージェント上で開始し、完了後に<code>on</code>Senderが開始された実行リソースへと実行制御を戻す。</li>
<li><code>on(sndr, sch, closure)</code> : <a href="sender.html">Sender</a><code>sndr</code>の完了後に、<a href="scheduler.html">Scheduler</a><code>sch</code>に関連付けられた実行リソースに属する実行エージェントへ実行を移し、<code>sndr</code>の完了結果をもってSenderアダプタクロージャ<code>closure</code>を実行し、Sender<code>sndr</code>が完了された実行リソースへと実行制御を戻す。</li>
</ul>
<p><code>on</code>は<a href="sender_adaptor_closure.html">パイプ可能Senderアダプタオブジェクト</a>であり、パイプライン記法をサポートする。</p>
<h2>効果</h2>
<h3>呼び出し式 <code>on(sch, sndr)</code></h3>
<p>説明用の式<code>sch</code>と<code>sndr</code>に対して、下記いずれかが<code>true</code>となるとき呼び出し式<code>on(sch, sndr)</code>は<a class="cpprefjp-defined-word" data-desc="プログラムが適格でないこと。コンパイルエラーなどになる" href="../../../implementation-compliance.html#dfn-ill-formed">不適格</a>となる。</p>
<ul>
<li><code>decltype((sch))</code>が<code><a href="scheduler.html">scheduler</a></code>を満たさない、もしくは</li>
<li><code>decltype((sndr))</code>が<code><a href="sender.html">sender</a></code>を満たさず、かつ<a href="sender_adaptor_closure.html">パイプ可能Senderアダプタクロージャオブジェクト</a>ではない、もしくは</li>
<li><code>decltype((sndr))</code>が<code><a href="sender.html">sender</a></code>を満たし、かつ<a href="sender_adaptor_closure.html">パイプ可能Senderアダプタクロージャオブジェクト</a>である。</li>
</ul>
<p>そうでなければ、呼び出し式<code>on(sch, sndr)</code>は下記と等価。</p>
<p><div class="codehilite"><pre><span></span><code><span class="n"><a href="make-sender.html">make-sender</a></span><span class="p">(</span><span class="n">on</span><span class="p">,</span><span class="w"> </span><span class="n">sch</span><span class="p">,</span><span class="w"> </span><span class="n">sndr</span><span class="p">)</span>
</code></pre></div>
</p>
<h3>呼び出し式 <code>on(sndr, sch, closure)</code></h3>
<p>説明用の式<code>sndr</code>, <code>sch</code>, <code>closure</code>に対して、下記いずれかが<code>true</code>となるとき呼び出し式<code>on(sndr, sch, closure)</code>は<a class="cpprefjp-defined-word" data-desc="プログラムが適格でないこと。コンパイルエラーなどになる" href="../../../implementation-compliance.html#dfn-ill-formed">不適格</a>となる。</p>
<ul>
<li><code>decltype((sch))</code>が<code><a href="scheduler.html">scheduler</a></code>を満たさない、もしくは</li>
<li><code>decltype((sndr))</code>が<code><a href="sender.html">sender</a></code>を満たさない、もしくは</li>
<li><code>closure</code>が<a href="sender_adaptor_closure.html">パイプ可能Senderアダプタクロージャオブジェクト</a>ではない。</li>
</ul>
<p>そうでなければ、呼び出し式<code>on(sndr, sch, closure)</code>は下記と等価。</p>
<p><div class="codehilite"><pre><span></span><code><span class="n"><a href="make-sender.html">make-sender</a></span><span class="p">(</span><span class="n">on</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="product-type.html">product-type</a></span><span class="p">{</span><span class="n">sch</span><span class="p">,</span><span class="w"> </span><span class="n">closure</span><span class="p">},</span><span class="w"> </span><span class="n">sndr</span><span class="p">)</span>
</code></pre></div>
</p>
<h3>Senderアルゴリズムタグ <code>on</code></h3>
<p>説明用の式<code>out_sndr</code>と<code>env</code>に対して、型<code>OutSndr</code>を<code>decltype((out_sndr))</code>とし、型<code>Env</code>を<code>decltype((env))</code>とする。<code><a href="sender-for.html">sender-for</a><OutSndr, on_t> == false</code>のとき、式<code>on.transform_sender(<a href="set_value.html">set_value</a>, out_sndr, env)</code>は<a class="cpprefjp-defined-word" data-desc="プログラムが適格でないこと。コンパイルエラーなどになる" href="../../../implementation-compliance.html#dfn-ill-formed">不適格</a>となる。</p>
<p>そうでなければ、式<code>on.transform_sender(<a href="set_value.html">set_value</a>, out_sndr, env)</code>は下記と等価。</p>
<p><div class="codehilite"><pre><span></span><code><span class="k">auto</span><span class="o">&&</span><span class="w"> </span><span class="p">[</span><span class="n">_</span><span class="p">,</span><span class="w"> </span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="n">child</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">out_sndr</span><span class="p">;</span>
<span class="k">if</span><span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="p">(</span><span class="n"><a href="scheduler.html">scheduler</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">data</span><span class="p">)</span><span class="o">></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">orig_sch</span><span class="w"> </span><span class="o">=</span>
<span class="w"> </span><span class="n"><a href="call-with-default.html">call-with-default</a></span><span class="p">(</span><span class="n"><a href="get_start_scheduler.html">get_start_scheduler</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="not-a-scheduler.html">not-a-scheduler()</a></span><span class="p">,</span><span class="w"> </span><span class="n">env</span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n"><a href="continues_on.html">continues_on</a></span><span class="p">(</span>
<span class="w"> </span><span class="n"><a href="starts_on.html">starts_on</a></span><span class="p">(</span><span class="n"><a href="../../utility/forward_like.html">std::forward_like</a></span><span class="o"><</span><span class="n">OutSndr</span><span class="o">></span><span class="p">(</span><span class="n">data</span><span class="p">),</span><span class="w"> </span><span class="n"><a href="../../utility/forward_like.html">std::forward_like</a></span><span class="o"><</span><span class="n">OutSndr</span><span class="o">></span><span class="p">(</span><span class="n">child</span><span class="p">)),</span>
<span class="w"> </span><span class="n"><a href="../../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">orig_sch</span><span class="p">));</span>
<span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">auto</span><span class="o">&</span><span class="w"> </span><span class="p">[</span><span class="n">sch</span><span class="p">,</span><span class="w"> </span><span class="n">closure</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">data</span><span class="p">;</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">orig_sch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="call-with-default.html">call-with-default</a></span><span class="p">(</span>
<span class="w"> </span><span class="n"><a href="get_completion_scheduler.html">get_completion_scheduler</a></span><span class="o"><</span><span class="n"><a href="set_value.html">set_value_t</a></span><span class="o">></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="not-a-scheduler.html">not-a-scheduler()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="get_env.html">get_env</a></span><span class="p">(</span><span class="n">child</span><span class="p">),</span><span class="w"> </span><span class="n">env</span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n"><a href="continues_on.html">continues_on</a></span><span class="p">(</span>
<span class="w"> </span><span class="n"><a href="../../utility/forward_like.html">std::forward_like</a></span><span class="o"><</span><span class="n">OutSndr</span><span class="o">></span><span class="p">(</span><span class="n">closure</span><span class="p">)(</span><span class="n"><a href="continues_on.html">continues_on</a></span><span class="p">(</span><span class="n"><a href="../../utility/forward_like.html">std::forward_like</a></span><span class="o"><</span><span class="n">OutSndr</span><span class="o">></span><span class="p">(</span><span class="n">child</span><span class="p">),</span><span class="w"> </span><span class="n">sch</span><span class="p">)),</span>
<span class="w"> </span><span class="n">orig_sch</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>カスタマイゼーションポイント</h2>
<p><a href="receiver.html">Receiver</a>との<a href="connect.html">接続(connect)</a>時に、関連付けられた実行ドメインに対して<code><a href="transform_sender.html">execution::transform_sender</a></code>経由でSender変換が行われる。
<a href="default_domain.html">デフォルト実行ドメイン</a>では<code>on.transform_sender(<a href="set_value.html">set_value</a>, out_sndr, env)</code>が呼ばれ、前述仕様通りのSenderへと変換される。</p>
<h3>呼び出し式 <code>on(sch, sndr)</code></h3>
<p>説明用の式<code>out_sndr</code>を<code>on(sch, sndr)</code>の<a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a><a href="sender.html">Sender</a>とし、型<code>OutSndr</code>を<code>decltype((out_sndr))</code>とする。式<code>out_rcvr</code>を<code><a href="sender_in.html">sender_in</a><OutSndr, Env> == true</code>となる<a href="../queryable.html">環境</a><code>Env</code>に関連付けられた<a href="receiver.html">Receiver</a>とする。<code>out_sndr</code>と<code>out_rcvr</code>との<a href="connect.html">接続(connect)</a>結果<a href="operation_state.html">Operation State</a>への左辺値参照を<code>op</code>としたとき、<code><a href="start.html">start</a>(op)</code>呼び出しは下記を満たすべき。</p>
<ul>
<li><code><a href="get_start_scheduler.html">get_start_scheduler</a>(<a href="get_env.html">get_env</a>(rcvr))</code>で取得した現在の<a href="scheduler.html">Scheduler</a>を記憶する。</li>
<li><a href="scheduler.html">Scheduler</a><code>sch</code>に関連付けられた実行リソースに属する実行エージェント上で<code>sndr</code>を開始する。</li>
<li><code>sndr</code>の完了後に、手順1で記憶したSchedulerに関連付けられた実行リソースに実行制御を戻す。</li>
<li><code>sndr</code>の非<a class="cpprefjp-defined-word" data-desc="マルチスレッド実行時にリソースの所有権に基づいて実行順序を制御する操作">同期操作</a>の結果を<code>out_rcvr</code>へ転送する。</li>
</ul>
<p>いずれかのスケジューリングが失敗した場合、<a class="cpprefjp-defined-word" data-desc="未規定の動作。事前の断りなく処理系によって異なる動作をする" href="../../../implementation-compliance.html#dfn-unspecified-behavior">未規定</a>の実行エージェント上で<code>out_rcvr</code>の<a href="set_error.html">エラー完了</a>が行われるべき。</p>
<h3>呼び出し式 <code>on(sndr, sch, closure)</code></h3>
<p>説明用の式<code>out_sndr</code>を<code>on(sndr, sch, closure)</code>の<a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a><a href="sender.html">Sender</a>とし、型<code>OutSndr</code>を<code>decltype((out_sndr))</code>とする。式<code>out_rcvr</code>を<code><a href="sender_in.html">sender_in</a><OutSndr, Env> == true</code>となる<a href="../queryable.html">環境</a><code>Env</code>に関連付けられた<a href="receiver.html">Receiver</a>とする。<code>out_sndr</code>と<code>out_rcvr</code>との<a href="connect.html">接続(connect)</a>結果<a href="operation_state.html">Operation State</a>への左辺値参照を<code>op</code>としたとき、<code><a href="start.html">start</a>(op)</code>呼び出しは下記を満たすべき。</p>
<ul>
<li>現在のSchedulerとして、<code><a href="get_completion_scheduler.html">get_completion_scheduler</a><<a href="set_value.html">set_value_t</a>>(<a href="get_env.html">get_env</a>(rcvr))</code>を記憶する。</li>
<li><code>sndr</code>を現在の実行エージェント上で開始する。</li>
<li><code>sndr</code>の完了後に、<a href="scheduler.html">Scheduler</a><code>sch</code>に関連付けられた実行リソースの実行エージェントに実行制御を移す。</li>
<li><code>sndr</code>の非<a class="cpprefjp-defined-word" data-desc="マルチスレッド実行時にリソースの所有権に基づいて実行順序を制御する操作">同期操作</a>の結果を、Sender<code>closure(S)</code>と接続して開始するかのように転送する。ここで<code>S</code>は<code>sndr</code>の非<a class="cpprefjp-defined-word" data-desc="マルチスレッド実行時にリソースの所有権に基づいて実行順序を制御する操作">同期操作</a>の結果と同期的に完了するSenderとする。</li>
<li>前手順で開始した非<a class="cpprefjp-defined-word" data-desc="マルチスレッド実行時にリソースの所有権に基づいて実行順序を制御する操作">同期操作</a>が完了したら、手順1で記憶したSchedulerに関連付けられた実行リソースに実行制御を戻し、非<a class="cpprefjp-defined-word" data-desc="マルチスレッド実行時にリソースの所有権に基づいて実行順序を制御する操作">同期操作</a>の結果を<code>out_rcvr</code>へ転送する。</li>
</ul>
<p>いずれかのスケジューリングが失敗した場合、<a class="cpprefjp-defined-word" data-desc="未規定の動作。事前の断りなく処理系によって異なる動作をする" href="../../../implementation-compliance.html#dfn-unspecified-behavior">未規定</a>の実行エージェント上で<code>out_rcvr</code>の<a href="set_error.html">エラー完了</a>が行われるべき。</p>
<h2>例</h2>
<h3>例1: on(sch, sndr)</h3>
<p><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../thread.html"><thread></a></span>
<span class="cp">#include <a href="../../print.html"><print></a></span>
<span class="cp">#include <a href="../../execution.html"><execution></a></span>
<span class="k">namespace</span><span class="w"> </span><span class="nn">ex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nn">std</span><span class="o">::</span><span class="nn">execution</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="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"main#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="run_loop.html">ex::run_loop</a></span><span class="w"> </span><span class="n">loop</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../thread/jthread.html">std::jthread</a></span><span class="w"> </span><span class="n">worker</span><span class="p">{[</span><span class="o">&</span><span class="p">]{</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"start worker#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="n">loop</span><span class="p">.</span><span class="n"><a href="run_loop/run.html">run()</a></span><span class="p">;</span>
<span class="w"> </span><span class="p">}};</span>
<span class="w"> </span><span class="n"><a href="scheduler.html">ex::scheduler</a></span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">sch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loop</span><span class="p">.</span><span class="n"><a href="run_loop/get_scheduler.html">get_scheduler()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="sender.html">ex::sender</a></span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">snd0</span><span class="w"> </span><span class="o">=</span>
<span class="w"> </span><span class="n"><a href="then.html">ex::then</a></span><span class="p">(</span><span class="n"><a href="just.html">ex::just</a></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="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"on worker#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="mi">6</span><span class="p">;</span>
<span class="w"> </span><span class="p">});</span>
<span class="w"> </span><span class="n"><a href="sender.html">ex::sender</a></span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">snd1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">ex::on</span></span><span class="p">(</span><span class="n">sch</span><span class="p">,</span><span class="w"> </span><span class="n">snd0</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="sender.html">ex::sender</a></span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">snd2</span><span class="w"> </span><span class="o">=</span>
<span class="w"> </span><span class="n"><a href="then.html">ex::then</a></span><span class="p">(</span><span class="n">snd1</span><span class="p">,</span><span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"on main#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">7</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="p">[</span><span class="n">val</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../this_thread/sync_wait.html">std::this_thread::sync_wait</a></span><span class="p">(</span><span class="n"><a href="../../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">snd2</span><span class="p">)).</span><span class="n"><a href="../../optional/optional/value.html">value()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"val={}"</span><span class="p">,</span><span class="w"> </span><span class="n">val</span><span class="p">);</span>
<span class="w"> </span><span class="n">loop</span><span class="p">.</span><span class="n"><a href="run_loop/finish.html">finish()</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h4>出力例</h4>
<p><pre><code>main#133519926773568
start worker#133519921645120
on worker#133519921645120
on main#133519926773568
val=42
</code></pre></p>
<h3>例2: on(sndr, sch, closure)</h3>
<p><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../thread.html"><thread></a></span>
<span class="cp">#include <a href="../../print.html"><print></a></span>
<span class="cp">#include <a href="../../execution.html"><execution></a></span>
<span class="k">namespace</span><span class="w"> </span><span class="nn">ex</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nn">std</span><span class="o">::</span><span class="nn">execution</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="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"main#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="run_loop.html">ex::run_loop</a></span><span class="w"> </span><span class="n">loop</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../thread/jthread.html">std::jthread</a></span><span class="w"> </span><span class="n">worker</span><span class="p">{[</span><span class="o">&</span><span class="p">]{</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"start worker#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="n">loop</span><span class="p">.</span><span class="n"><a href="run_loop/run.html">run()</a></span><span class="p">;</span>
<span class="w"> </span><span class="p">}};</span>
<span class="w"> </span><span class="n"><a href="scheduler.html">ex::scheduler</a></span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">sch</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">loop</span><span class="p">.</span><span class="n"><a href="run_loop/get_scheduler.html">get_scheduler()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="sender.html">ex::sender</a></span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">sndr</span><span class="w"> </span><span class="o">=</span>
<span class="w"> </span><span class="n"><a href="just.html">ex::just</a></span><span class="p">()</span>
<span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n"><a href="then.html">ex::then</a></span><span class="p">([]()</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"on main#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span>
<span class="w"> </span><span class="p">})</span>
<span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n"><span style="color:#ff0000">ex::on</span></span><span class="p">(</span><span class="n">sch</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="then.html">ex::then</a></span><span class="p">([](</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"on worker#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span>
<span class="w"> </span><span class="p">}))</span>
<span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n"><a href="then.html">ex::then</a></span><span class="p">([](</span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"on main#{}"</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../thread/this_thread/get_id.html">std::this_thread::get_id()</a></span><span class="p">);</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">7</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="p">[</span><span class="n">val</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../this_thread/sync_wait.html">std::this_thread::sync_wait</a></span><span class="p">(</span><span class="n"><a href="../../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">sndr</span><span class="p">)).</span><span class="n"><a href="../../optional/optional/value.html">value()</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"val={}"</span><span class="p">,</span><span class="w"> </span><span class="n">val</span><span class="p">);</span>
<span class="w"> </span><span class="n">loop</span><span class="p">.</span><span class="n"><a href="run_loop/finish.html">finish()</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h4>出力例</h4>
<p><pre><code>main#133519926773568
start worker#133519921645120
on main#133519926773568
on worker#133519921645120
on main#133519926773568
val=42
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++26</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>: ??</li>
<li><a href="../../../implementation.html#icc">ICC</a>: ??</li>
<li><a href="../../../implementation.html#visual_cpp">Visual C++</a>: ??</li>
</ul>
<h2>関連項目</h2>
<ul>
<li><code><a href="schedule.html">execution::schedule</a></code></li>
<li><code><a href="starts_on.html">execution::starts_on</a></code></li>
<li><code><a href="continues_on.html">execution::continues_on</a></code></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2300r10.html" target="_blank">P2300R10 <code>std::execution</code></a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p3557r3.html" target="_blank">P3557R3 High-Quality Sender Diagnostics with Constexpr Exceptions</a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3826r5.html" target="_blank">P3826R5 Fix Sender Algorithm Customization</a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2026/p3941r4.html" target="_blank">P3941R4 Scheduler Affinity</a></li>
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