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最終更新日時(UTC):
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2026年02月24日 07時56分31秒
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<span itemprop="name">Akira Takahashi</span>
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<div class="identifier-type">customization point object</div><div class="header"><compare></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">weak_order</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="kr">inline</span><span class="w"> </span><span class="k">namespace</span><span class="w"> </span><span class="cm">/*unspecified*/</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="cm">/*unspecified*/</span><span class="w"> </span><span class="n">weak_order</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="cm">/*unspecified*/</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><code>weak_order</code>は2つの引数を受け取り、それらを弱順序の上で比較する関数オブジェクトである。</p>
<h2>効果</h2>
<p><code>weak_order(a, b)</code>のように呼び出された時、以下のいずれかと等価（上から順に考慮される）</p>
<ol>
<li>
<p><code><a href="../type_traits/decay.html">decay</a></code>を通した<code>a, b</code>の型が異なる場合、呼び出しは<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>（コンパイルエラー）</p>
</li>
<li>
<p><code>weak_order(a, b)</code>の<code>weak_order</code>の意味が<a class="cpprefjp-defined-word" data-desc="実引数依存の名前探索 (Argument Dependent Lookup)。引数の型が所属する名前空間の関数を探索する言語機能">ADL</a>のみによって決まるコンテキストで、<code><a href="weak_ordering.html">weak_ordering</a>(weak_order(a, b))</code>が呼び出し可能ならば<code>weak_ordering(weak_order(a, b))</code></p>
</li>
<li>
<p><code><a href="../type_traits/decay.html">decay</a></code>を通した<code>a, b</code>の型<code>T</code>が浮動小数点型の場合、<code>T</code>の組み込みの比較演算子および<code><a href="strong_order.html">strong_order</a></code>による順序と一貫する<code><a href="weak_ordering.html">weak_ordering</a></code>の値を返す。<br />
さらに、<code><a href="../limits/numeric_limits/is_iec559.html">numeric_limits<T>::is_iec559</a> == true</code>の場合、追加で以下の同値類の順序に従った順序付けを行う。</p>
<ol>
<li>全ての<code>-NaN</code></li>
<li><code>-Inf</code></li>
<li>負の正規化数</li>
<li>負の非正規化数</li>
<li><code>±0.0</code></li>
<li>正の非正規化数</li>
<li>正の正規化数</li>
<li><code>+Inf</code></li>
<li>全ての<code>+NaN</code></li>
</ol>
</li>
<li>
<p><code><a href="weak_ordering.html">weak_ordering</a>(a <=> b)</code>が呼び出し可能ならば<code>weak_ordering(a <=> b)</code></p>
</li>
<li>
<p><code><a href="weak_ordering.html">weak_ordering(</a><a href="strong_order.html">strong_order</a>(a, b))</code>が呼び出し可能ならば<code>weak_ordering(strong_order(a, b))</code></p>
</li>
<li>
<p>それ以外の場合、呼び出しは<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>。</p>
</li>
</ol>
<h2><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></h2>
<p>呼び出しが<a class="cpprefjp-defined-word" data-desc="プログラムが文法規則・診断対象の意味規則・単一定義規則を満たすこと" href="../../implementation-compliance.html#dfn-well-formed">適格</a>ならば、比較結果を表す<code><a href="weak_ordering.html">weak_ordering</a></code>の値。</p>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<p>上記「効果」節のそれぞれのケース毎に</p>
<ol>
<li>--</li>
<li>呼び出される<code>weak_order(a, b)</code>およびその<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>の<code>weak_ordering</code>への変換が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出するかに従う。</li>
<li>投げない。</li>
<li>呼び出される<code>a <=> b</code>およびその<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>の<code>weak_ordering</code>への変換が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出するかに従う。</li>
<li>呼び出される<code><a href="strong_order.html">strong_order</a>(a, b)</code>およびその<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>の<code>weak_ordering</code>への変換が<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出するかに従う。</li>
</ol>
<h2>定数式に評価される条件</h2>
<p>上記「効果」節のそれぞれのケース毎に</p>
<ol>
<li>--</li>
<li>呼び出される<code>weak_order(a, b)</code>およびその<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>の<code>weak_ordering</code>への変換が定数評価可能であるかに従う。</li>
<li>常に定数評価可能</li>
<li>呼び出される<code>a <=> b</code>およびその<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>の<code>weak_ordering</code>への変換が定数評価可能であるかに従う。</li>
<li>呼び出される<code><a href="strong_order.html">strong_order</a>(a, b)</code>およびその<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>の<code>weak_ordering</code>への変換が定数評価可能であるかに従う。</li>
</ol>
<h2>カスタマイゼーションポイント</h2>
<p>上記「効果」節2,4,5のケースでは、<a class="cpprefjp-defined-word" data-desc="プログラム定義。ユーザー（プログラマ）によって定義されること（標準ライブラリで定義されるものを除く）">ユーザー定義</a>の<code>weak_order()</code>、<code><=></code>演算子を定義、もしくは<code>strong_order()</code>へアダプトしておくことによって実行される比較をカスタマイズすることができる。</p>
<ol>
<li>--</li>
<li>引数<code>a, b</code>の型<code>T</code>と同じ名前空間、もしくは<code>T</code>の定義内で<code>friend</code>関数として<code>weak_order()</code>を定義しておく。</li>
<li>--</li>
<li>引数<code>a, b</code>の型<code>T</code>に対して、使用可能な<code><=></code>演算子を定義しておく。</li>
<li>引数<code>a, b</code>の型<code>T</code>を<code><a href="strong_order.html">strong_order</a></code>にアダプトしておく。</li>
</ol>
<p>ただし、どのケースにおいてもその<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>型は<code><a href="weak_ordering.html">weak_ordering</a></code>に変換可能でなければならない。</p>
<h2>備考</h2>
<p><code><a href="../limits/numeric_limits/is_iec559.html">numeric_limits<T>::is_iec559</a> == true</code>の場合の浮動小数点数の比較において、各同値類間の順序は以下のようになる。</p>
<p>{全ての<code>-NaN</code>} <code><</code> {<code>-Inf</code>} <code><</code> {負の正規化数} <code><</code> {負の非正規化数} <code><</code> {<code>±0.0</code>} <code><</code> {正の非正規化数} <code><</code> {正の正規化数} <code><</code> {<code>+Inf</code>} <code><</code> {全ての<code>+NaN</code>}</p>
<p>それぞれの同値類における順序付けは通常の比較演算子の順序付けに従う。ただし、比較不能である場合はその値は同値として扱われる。すなわち、{<code>±0.0</code>}および{<code>±NaN</code>}のそれぞの同値類では全ての値が同値(<code>=</code>)として扱われる。</p>
<h2>例</h2>
<p><div class="yata" id="716f32e0309c36e9696e285fc1436bb63263744c"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../compare.html"><compare></a></span>
<span class="cp">#include <a href="../limits.html"><limits></a></span>
<span class="k">struct</span><span class="w"> </span><span class="nc">no_spaceship</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">n1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="k">friend</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">no_spaceship</span><span class="o">&</span><span class="w"> </span><span class="n">lhs</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">no_spaceship</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">std</span><span class="o">::</span><span class="n">weak_ordering</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//1 -> 3 -> 2の順で比較</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lhs</span><span class="p">.</span><span class="n">n1</span><span class="w"> </span><span class="o"><=></span><span class="w"> </span><span class="n">rhs</span><span class="p">.</span><span class="n">n1</span><span class="p">;</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">cmp</span><span class="p">;</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lhs</span><span class="p">.</span><span class="n">n3</span><span class="w"> </span><span class="o"><=></span><span class="w"> </span><span class="n">rhs</span><span class="p">.</span><span class="n">n3</span><span class="p">;</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">cmp</span><span class="p">;</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">lhs</span><span class="p">.</span><span class="n">n2</span><span class="w"> </span><span class="o"><=></span><span class="w"> </span><span class="n">rhs</span><span class="p">.</span><span class="n">n2</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">};</span>
<span class="k">struct</span><span class="w"> </span><span class="nc">have_spaceship</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">n3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="k">friend</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="k">operator</span><span class="o"><=></span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">have_spaceship</span><span class="o">&</span><span class="w"> </span><span class="n">lhs</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">have_spaceship</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">std</span><span class="o">::</span><span class="n">weak_ordering</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//宣言と逆順で比較</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lhs</span><span class="p">.</span><span class="n">n3</span><span class="w"> </span><span class="o"><=></span><span class="w"> </span><span class="n">rhs</span><span class="p">.</span><span class="n">n3</span><span class="p">;</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">cmp</span><span class="p">;</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lhs</span><span class="p">.</span><span class="n">n2</span><span class="w"> </span><span class="o"><=></span><span class="w"> </span><span class="n">rhs</span><span class="p">.</span><span class="n">n2</span><span class="p">;</span><span class="w"> </span><span class="n">cmp</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">cmp</span><span class="p">;</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">lhs</span><span class="p">.</span><span class="n">n1</span><span class="w"> </span><span class="o"><=></span><span class="w"> </span><span class="n">rhs</span><span class="p">.</span><span class="n">n1</span><span class="p">;</span>
<span class="w"> </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="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ios/boolalpha.html">std::boolalpha</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">//2. ユーザー定義<span style="color:#ff0000">weak_order</span>()によるカスタム比較</span>
<span class="w"> </span><span class="n">no_spaceship</span><span class="w"> </span><span class="n">s1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="n">s2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">3</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="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="n">s1</span><span class="p">,</span><span class="w"> </span><span class="n">s2</span><span class="p">)</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="p">)</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="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">"</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
<span class="w"> </span><span class="c1">//3. 浮動小数点数の比較</span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">qnan</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../limits/numeric_limits.html">std::numeric_limits</a></span><span class="o"><</span><span class="kt">double</span><span class="o">>::</span><span class="n">quiet_NaN</span><span class="p">();</span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">snan</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../limits/numeric_limits.html">std::numeric_limits</a></span><span class="o"><</span><span class="kt">double</span><span class="o">>::</span><span class="n">signaling_NaN</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="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="mf">-0.0</span><span class="p">,</span><span class="w"> </span><span class="o">+</span><span class="mf">0.0</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">)</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="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="o">-</span><span class="n">qnan</span><span class="p">,</span><span class="w"> </span><span class="o">+</span><span class="n">qnan</span><span class="p">)</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="p">)</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="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="n">qnan</span><span class="p">,</span><span class="w"> </span><span class="n">snan</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">)</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="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">"</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
<span class="w"> </span><span class="c1">//4. ユーザー定義<=>によるカスタム比較</span>
<span class="w"> </span><span class="n">have_spaceship</span><span class="w"> </span><span class="n">s3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="n">s4</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">3</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="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="n">s3</span><span class="p">,</span><span class="w"> </span><span class="n">s4</span><span class="p">)</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="p">)</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="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">"</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
<span class="w"> </span><span class="c1">//4. 組み込み型の比較</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="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><span style="color:#ff0000">weak_order</span></span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">)</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">0</span><span class="p">)</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>true
true
true
true
false
true
</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>: 10.1 <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/consistent_comparison.html">C++20 <code><=></code>/<code>==</code>による比較演算子の自動定義</a></li>
<li><code><a href="strong_order.html">strong_order</a></code></li>
<li><code><a href="weak_ordering.html">weak_ordering</a></code></li>
<li><code><a href="compare_weak_order_fallback.html">compare_weak_order_fallback</a></code></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="http://wg21.link/p0768" target="_blank">P0768R1 Library support for the spaceship (comparison) operator</a></li>
<li><a href="http://wg21.link/p1614" target="_blank">P1614R2 The Mothership has Landed (Adding <=> to the Library)</a></li>
<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2602r2.html" target="_blank">P2602R2 Poison Pills are Too Toxic</a></li>
</ul></div>
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