cpprefjp
diff --git a/‎lang/cpp23/feature_test_macros.html‎
Lines changed: 16 additions & 2 deletions b/‎lang/cpp23/feature_test_macros.html‎
Lines changed: 16 additions & 2 deletions
diff --git a/‎reference/variant/variant.html‎
Lines changed: 39 additions & 4 deletions b/‎reference/variant/variant.html‎
Lines changed: 39 additions & 4 deletions
@@ -189,8 +189,8 @@
     <p class="text-right"><small>
       最終更新日時:
       <time itemprop="datePublished" class="js-local-time"
-            datetime="2026-08-19T22:22:51+09:00">
-        2026年08月19日 22時22分51秒 (JST)
+            datetime="2026-08-31T12:27:20+09:00">
+        2026年08月31日 12時27分20秒 (JST)
       </time>
       <br/>
       <span itemprop="author" itemscope itemtype="http://schema.org/Person">
@@ -697,6 +697,12 @@ <h3>ライブラリ</h3>
 <td><code><a href="../../reference/utility.html">&lt;utility&gt;</a></code></td>
 </tr>
 <tr>
+<td><code>__cpp_lib_variant</code></td>
+<td><code>202106L</code></td>
+<td><code>202102L</code> : <code><a href="../../reference/variant/variant.html">std::variant</a></code>から派生した型を<code><a href="../../reference/variant/visit.html">std::visit()</a></code>に渡せるようにする<br /><code>202106L</code> : <code><a href="../../reference/variant/variant.html">std::variant</a></code>の一部のメンバ関数を<code>constexpr</code>にする</td>
+<td><code><a href="../../reference/variant.html">&lt;variant&gt;</a></code></td>
+</tr>
+<tr>
 <td><code>__cpp_lib_print</code></td>
 <td><code>202403L</code></td>
 <td><code><a href="../../reference/print.html">&lt;print&gt;</a></code>の追加</td>
@@ -707,6 +713,14 @@ <h3>ライブラリ</h3>
 <h2>参照</h2>
 <ul>
 <li><a href="https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations" target="_blank">SD-FeatureTest: Feature-Test Macros and Policies - isocpp</a></li>
+<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2162r2.html" target="_blank">P2162R2 Inheriting from <code>std::variant</code></a><ul>
+<li>C++23で、<code>__cpp_lib_variant</code>が<code>202102L</code>に更新された</li>
+</ul>
+</li>
+<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2231r1.html" target="_blank">P2231R1 Missing <code>constexpr</code> in <code>std::optional</code> and <code>std::variant</code></a><ul>
+<li>C++23で、<code>__cpp_lib_variant</code>が<code>202106L</code>に更新された</li>
+</ul>
+</li>
 <li><a href="https://cplusplus.github.io/LWG/issue3621" target="_blank">LWG Issue 3621. Remove feature-test macro <code>__cpp_lib_monadic_optional</code></a><ul>
 <li>C++23で、重複していた<code>__cpp_lib_monadic_optional</code>が削除され、代わりに<code>__cpp_lib_optional</code>が<code>202106L</code>から<code>202110L</code>に更新された（<code>optional</code>のモナド操作を表す）</li>
 </ul>
 
@@ -68,7 +68,7 @@
 
     </head>
     <body>
-<header data-kunai-mdinfo="{&#34;meta&#34;: {&#34;header&#34;: [&#34;variant&#34;], &#34;namespace&#34;: [&#34;std&#34;], &#34;id-type&#34;: [&#34;class template&#34;], &#34;cpp&#34;: [&#34;cpp17&#34;]}, &#34;sources&#34;: [{&#34;id&#34;: &#34;3b47c816ac6bb87d13aeb5f8ce7fe81e0ebcf57d&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;variant&gt;\n#include &lt;string&gt;\n\nint main()\n{\n  // int, char, std::string\u306e\u3044\u305a\u308c\u304b\u306e\u578b\u306e\u5024\u3092\u4fdd\u6301\u3067\u304d\u308b\u578b\n  std::variant&lt;int, char, std::string&gt; v = 3; // int\u578b\u306e\u5024\u3092\u4ee3\u5165\n\n  // \u5019\u88dc\u578b\u306e0\u756a\u76ee\u306e\u578b (int) \u3092\u4fdd\u6301\u3057\u3066\u3044\u308b\u304b\n  if (v.index() == 0) {\n    int&amp; x = std::get&lt;0&gt;(v); // \u578b\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u6307\u5b9a\u3057\u3066\u3001\u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u3092\u53d6\u5f97\n    std::cout &lt;&lt; x &lt;&lt; std::endl;\n  }\n\n  v = std::string(\&#34;Hello\&#34;); // std::string\u578b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4ee3\u5165\n\n  // std::string\u578b\u3092\u4fdd\u6301\u3057\u3066\u3044\u308b\u304b\n  if (std::holds_alternative&lt;std::string&gt;(v)) {\n    std::string&amp; x = std::get&lt;std::string&gt;(v); // \u578b\u3092\u6307\u5b9a\u3057\u3066\u3001\u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u3092\u53d6\u5f97\n    std::cout &lt;&lt; x &lt;&lt; std::endl;\n  }\n}\n&#34;}], &#34;page_id&#34;: [&#34;reference&#34;, &#34;variant&#34;, &#34;variant&#34;]}">
+<header data-kunai-mdinfo="{&#34;meta&#34;: {&#34;header&#34;: [&#34;variant&#34;], &#34;namespace&#34;: [&#34;std&#34;], &#34;id-type&#34;: [&#34;class template&#34;], &#34;cpp&#34;: [&#34;cpp17&#34;]}, &#34;sources&#34;: [{&#34;id&#34;: &#34;3b47c816ac6bb87d13aeb5f8ce7fe81e0ebcf57d&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;variant&gt;\n#include &lt;string&gt;\n\nint main()\n{\n  // int, char, std::string\u306e\u3044\u305a\u308c\u304b\u306e\u578b\u306e\u5024\u3092\u4fdd\u6301\u3067\u304d\u308b\u578b\n  std::variant&lt;int, char, std::string&gt; v = 3; // int\u578b\u306e\u5024\u3092\u4ee3\u5165\n\n  // \u5019\u88dc\u578b\u306e0\u756a\u76ee\u306e\u578b (int) \u3092\u4fdd\u6301\u3057\u3066\u3044\u308b\u304b\n  if (v.index() == 0) {\n    int&amp; x = std::get&lt;0&gt;(v); // \u578b\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u3092\u6307\u5b9a\u3057\u3066\u3001\u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u3092\u53d6\u5f97\n    std::cout &lt;&lt; x &lt;&lt; std::endl;\n  }\n\n  v = std::string(\&#34;Hello\&#34;); // std::string\u578b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4ee3\u5165\n\n  // std::string\u578b\u3092\u4fdd\u6301\u3057\u3066\u3044\u308b\u304b\n  if (std::holds_alternative&lt;std::string&gt;(v)) {\n    std::string&amp; x = std::get&lt;std::string&gt;(v); // \u578b\u3092\u6307\u5b9a\u3057\u3066\u3001\u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u3092\u53d6\u5f97\n    std::cout &lt;&lt; x &lt;&lt; std::endl;\n  }\n}\n&#34;}, {&#34;id&#34;: &#34;4ac7c00fd45ad81619e340a74863eafb82c72340&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;variant&gt;\n#include &lt;string&gt;\n\n// variant\u3092\u7d99\u627f\u3057\u3001\u72ec\u81ea\u306e\u64cd\u4f5c\u3092\u8ffd\u52a0\u3059\u308b\nstruct Value : std::variant&lt;int, std::string&gt; {\n  using variant::variant;\n\n  bool is_string() const\n  {\n    return std::holds_alternative&lt;std::string&gt;(*this);\n  }\n};\n\nint main()\n{\n  Value v = std::string(\&#34;Hello\&#34;);\n\n  std::cout &lt;&lt; std::boolalpha &lt;&lt; v.is_string() &lt;&lt; std::endl;\n\n  // C++23\u304b\u3089\u3001\u7d99\u627f\u3057\u305f\u578b\u3082std::visit()\u306b\u6e21\u305b\u308b\n  std::visit([](const auto&amp; x) { std::cout &lt;&lt; x &lt;&lt; std::endl; }, v);\n}\n&#34;}], &#34;page_id&#34;: [&#34;reference&#34;, &#34;variant&#34;, &#34;variant&#34;]}">
   <nav class="navbar navbar-default" role="navigation">
     <div class="container-fluid">
       <div class="navbar-header">
@@ -189,8 +189,8 @@
     <p class="text-right"><small>
       最終更新日時:
       <time itemprop="datePublished" class="js-local-time"
-            datetime="2026-08-24T23:57:44+09:00">
-        2026年08月24日 23時57分44秒 (JST)
+            datetime="2026-08-31T12:27:20+09:00">
+        2026年08月31日 12時27分20秒 (JST)
       </time>
       <br/>
       <span itemprop="author" itemscope itemtype="http://schema.org/Person">
@@ -510,6 +510,7 @@ <h2>ハッシュサポート</h2>
 </tbody>
 </table>
 <h2>例</h2>
+<h3>基本的な使い方</h3>
 <p><div class="yata" id="3b47c816ac6bb87d13aeb5f8ce7fe81e0ebcf57d"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
 <span class="cp">#include <a href="../variant.html">&lt;variant&gt;</a></span>
 <span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
@@ -535,10 +536,40 @@ <h2>例</h2>
 <span class="p">}</span>
 </code></pre></div>
 </div></p>
-<h3>出力</h3>
+<h4>出力</h4>
 <p><pre><code>3
 Hello
 </code></pre></p>
+<h3><code>variant</code>を継承して操作を追加する (C++23)</h3>
+<p><div class="yata" id="4ac7c00fd45ad81619e340a74863eafb82c72340"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html">&lt;iostream&gt;</a></span>
+<span class="cp">#include <a href="../variant.html">&lt;variant&gt;</a></span>
+<span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
+
+<span class="c1">// variantを継承し、独自の操作を追加する</span>
+<span class="k">struct</span><span class="w"> </span><span class="nc">Value</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n"><a href="">std::variant</a></span><span class="o">&lt;</span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">&gt;</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">variant</span><span class="o">::</span><span class="n">variant</span><span class="p">;</span>
+
+<span class="w">  </span><span class="kt">bool</span><span class="w"> </span><span class="nf">is_string</span><span class="p">()</span><span class="w"> </span><span class="k">const</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="holds_alternative.html">std::holds_alternative</a></span><span class="o">&lt;</span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">&gt;</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="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">Value</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="p">(</span><span class="s">"Hello"</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">&lt;&lt;</span><span class="w"> </span><span class="n"><a href="../ios/boolalpha.html">std::boolalpha</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">v</span><span class="p">.</span><span class="n">is_string</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</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="c1">// C++23から、継承した型も<a href="visit.html">std::visit</a>()に渡せる</span>
+<span class="w">  </span><span class="n"><a href="visit.html">std::visit</a></span><span class="p">([](</span><span class="k">const</span><span class="w"> </span><span class="k">auto</span><span class="o">&amp;</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"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">&lt;&lt;</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="p">},</span><span class="w"> </span><span class="n">v</span><span class="p">);</span>
+<span class="p">}</span>
+</code></pre></div>
+</div></p>
+<h4>出力</h4>
+<p><pre><code>true
+Hello
+</code></pre></p>
 <h2>バージョン</h2>
 <h3>言語</h3>
 <ul>
@@ -573,6 +604,10 @@ <h2>参照</h2>
 <li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0110r0.html" target="_blank">P0110R0 Implementing the strong guarantee for <code>variant&lt;&gt;</code> assignment</a></li>
 <li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0308r0.html" target="_blank">P0308R0 Valueless Variants Considered Harmful</a></li>
 <li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0510r0.html" target="_blank">P0510R0 Disallowing references, incomplete types, arrays, and empty variants</a></li>
+<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2162r2.html" target="_blank">P2162R2 Inheriting from <code>std::variant</code></a><ul>
+<li>C++23で、<code>variant</code>をpublic継承した型も<code><a href="visit.html">std::visit()</a></code>に渡せるようになった</li>
+</ul>
+</li>
 <li><a href="https://cplusplus.github.io/LWG/issue2901" target="_blank">LWG Issue 2901. <code>variant</code>s cannot properly support allocators</a><ul>
 <li>C++17の策定中に、アロケータ対応のコンストラクタと<code>uses_allocator</code>の特殊化が削除された（公開されたC++17にはこれらは存在しない）。<code>variant</code>は後続の値の代入で構築時のアロケータが失われるため、適切なアロケータ対応ができないという理由による</li>
 </ul>