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<header data-kunai-mdinfo="{"meta": {"header": ["tuple"], "namespace": ["std"], "id-type": ["class template"], "cpp": ["cpp11"]}, "sources": [{"id": "07164ae34d3e304394695ac8a56ded4eab93763f", "source": "#include <iostream>\n#include <tuple>\n#include <string>\n\nint main()\n{\n // 3\u8981\u7d20\u306e\u30bf\u30d7\u30eb\u3092\u4f5c\u308b\n std::tuple<int, char, std::string> t = std::make_tuple(1, 'a', \"hello\");\n\n // 0\u756a\u76ee\u306e\u8981\u7d20\u3092\u53c2\u7167\n int& i = std::get<0>(t);\n std::cout << i << std::endl;\n\n // 2\u756a\u76ee\u306e\u8981\u7d20\u3092\u53c2\u7167\n std::string& s = std::get<2>(t);\n std::cout << s << std::endl;\n}\n"}, {"id": "ee14232081b3b906eacf22ba5c3e3a62445b0e7e", "source": "#include <iostream>\n#include <tuple>\n#include <string>\n\n// \u95a2\u6570\u304b\u3089\u8907\u6570\u306e\u5024\u3092\u8fd4\u3059\nstd::tuple<int, char, std::string> f()\n{\n // std::make_tuple()\u306f\u307b\u3068\u3093\u3069\u306e\u72b6\u6cc1\u3067\u5fc5\u8981\u306a\u3044\n return {1, 'a', \"hello\"};\n}\n\nint main()\n{\n // \u69cb\u9020\u5316\u675f\u7e1b\u3067\u30bf\u30d7\u30eb\u3092\u5206\u89e3\u3057\u3066\u3001\u305d\u308c\u305e\u308c\u306e\u8981\u7d20\u3092\u4ee3\u5165\n auto [a, b, c] = f();\n\n std::cout << a << std::endl;\n std::cout << b << std::endl;\n std::cout << c << std::endl;\n}\n"}, {"id": "6df5b83a3e1e5e618524fd136245334be760d339", "source": "#include <iostream>\n#include <tuple>\n#include <string_view>\n#include <format>\n#include <utility>\n\nstruct A\n{\n A(int i, double d)\n : i(i)\n , d(d)\n {}\n\n std::tuple<int&, double&> f()\n {\n // this \u304c A* \u306a\u306e\u3067\n // i: int\n // d: double\n // \u3068\u3044\u3046\u3053\u3068\u3068\u540c\u3058\n return {i, d};\n }\n\n std::tuple<const int&, const double&> f() const\n {\n // this \u304c const A* \u306a\u306e\u3067\n // i: const int\n // d: const double\n // \u3068\u3044\u3046\u3053\u3068\u3068\u540c\u3058\n return {i, d};\n }\n\nprivate:\n int i;\n double d;\n};\n\nint main()\n{\n // \u30d7\u30ed\u30ad\u30b7\u53c2\u7167\u3067\u3042\u308b tuple \u306e\u6027\u8cea\n {\n A a{0, 0.0};\n\n // std::tuple<int&, double&>\n /***/ auto /***/ proxy = a.f();\n\n // const std::tuple<int&, double&>\n const auto const_proxy = a.f();\n\n // std::tuple<const int&, const double&>\n /***/ auto /***/ proxy_to_const = std::as_const(a).f();\n\n // const std::tuple<const int&, const double&>\n const auto const_proxy_to_const = std::as_const(a).f();\n\n // OK\uff08\u5404\u8981\u7d20\u304c\u6307\u3059\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u5024\u306b\u3064\u3044\u3066\u3001\u4ee3\u5165\u64cd\u4f5c\u304c\u306a\u3055\u308c\u308b\uff09\n proxy = a.f();\n const_proxy = a.f();\n\n // NG\uff08\u5404\u8981\u7d20\u304c\u6307\u3059\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u5909\u66f4\u3067\u304d\u306a\u3044\uff01\uff09\n // proxy_to_const = a.f();\n // const_proxy_to_const = a.f();\n }\n\n // \u4f7f\u3044\u65b9\n {\n auto print = [](std::string_view prefix, A& a) {\n\n // \u69cb\u9020\u5316\u675f\u7e1b\u3067\u5206\u89e3\n // i: int&\n // d: double&\n auto [i, d] = a.f();\n\n std::cout << std::format(\"{}: i={}, d={}\\n\", prefix, i, d);\n };\n\n A a{0, 0.0}, b{1, 1.0};\n\n print(\"before a\", a);\n print(\"before b\", b);\n\n // \u30d7\u30ed\u30ad\u30b7\u53c2\u7167\u3068\u3057\u3066\u4f7f\u3048\u308b tuple \u540c\u58eb\u306e swap \u64cd\u4f5c\u3067\n // \u554f\u984c\u306a\u304f\u5404\u8981\u7d20\u304c\u6307\u3059\u5148\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306b\u3064\u3044\u3066 swap \u64cd\u4f5c\u304c\u884c\u3048\u308b\n std::ranges::swap(a.f(), b.f());\n\n print(\"after a\", a);\n print(\"after b\", b);\n }\n}\n"}], "page_id": ["reference", "tuple", "tuple"]}">
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<div class="identifier-type">class template</div><div class="header"><tuple></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">tuple</span><span class="cpp cpp11" title="C++11で追加">(C++11)</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">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="p">...</span><span class="w"> </span><span class="n">Args</span><span class="o">></span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc"><a href="">tuple</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code>tuple</code>型は、複数の型の値を保持する「タプル」を表現するためのクラスである。</p>
<p><code><a href="../utility/pair.html">pair</a></code>型は2つの型の値を保持する「組」を表現することができるが、<code>tuple</code>ではN個の型の値を扱うことができる。</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><a href="tuple/op_constructor.html">(constructor)</a></code></td>
<td>コンストラクタ</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/op_assign.html">operator=</a></code></td>
<td>代入演算子</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/swap.html">swap</a></code></td>
<td>異なる<code>tuple</code>オブジェクトと値を入れ替える</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>非メンバ関数</h2>
<h3>タプル生成関数</h3>
<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><a href="ignore.html">ignore</a></code></td>
<td>無視する要素のプレースホルダー(constant variable)</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="make_tuple.html">make_tuple</a></code></td>
<td>引数のコピーからタプルを生成する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="forward_as_tuple.html">forward_as_tuple</a></code></td>
<td>引数の完全な型からタプルを生成する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tie.html">tie</a></code></td>
<td>引数への参照からタプルを生成する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple_cat.html">tuple_cat</a></code></td>
<td>複数のタプルから1つのタプルを生成する</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h3>要素アクセス</h3>
<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><a href="tuple/get.html">get</a></code></td>
<td><code>tuple</code>の<code>i</code>番目の要素を参照する</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h3>入れ替え</h3>
<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><a href="tuple/swap_free.html">swap</a></code></td>
<td>2つの<code>tuple</code>オブジェクトを入れ替える</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h3>比較演算子</h3>
<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><a href="tuple/op_equal.html">operator==</a></code></td>
<td>等値比較を行う</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/op_not_equal.html">operator!=</a></code></td>
<td>非等値比較を行う</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/op_compare_3way.html">operator<=></a></code></td>
<td>三方比較を行う</td>
<td>C++20</td>
</tr>
<tr>
<td><code><a href="tuple/op_less.html">operator<</a></code></td>
<td>左辺が右辺よりも小さいか比較を行う</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/op_less_equal.html">operator<=</a></code></td>
<td>左辺が右辺以下か比較を行う</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/op_greater.html">operator></a></code></td>
<td>左辺が右辺より大きいか比較を行う</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="tuple/op_greater_equal.html">operator>=</a></code></td>
<td>左辺が右辺以上か比較を行う</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>推論補助</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><a href="tuple/op_deduction_guide.html">(deduction_guide)</a></code></td>
<td>クラステンプレートの推論補助</td>
<td>C++17</td>
</tr>
</tbody>
</table>
<h2>tuple-like とのユーティリティ</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><a href="tuple/op_equal.html">operator==</a></code></td>
<td><code><a href="tuple-like.html">tuple-like</a></code>なオブジェクトとの等値比較を行う</td>
<td>C++23</td>
</tr>
<tr>
<td><code><a href="tuple/op_compare_3way.html">operator<=></a></code></td>
<td><code><a href="tuple-like.html">tuple-like</a></code>なオブジェクトとの三方比較を行う</td>
<td>C++23</td>
</tr>
<tr>
<td><code><a href="tuple/common_type.html">common_type</a></code></td>
<td><code><a href="tuple-like.html">tuple-like</a></code>なオブジェクトとの共通型を取得できるようにする特殊化</td>
<td>C++23</td>
</tr>
<tr>
<td><code><a href="tuple/basic_common_reference.html">basic_common_reference</a></code></td>
<td><code><a href="tuple-like.html">tuple-like</a></code>なオブジェクトとの共通の参照型を取得出来るようにする特殊化</td>
<td>C++23</td>
</tr>
</tbody>
</table>
<h2>例</h2>
<h3>基本的な使い方 (C++11)</h3>
<p><div class="yata" id="07164ae34d3e304394695ac8a56ded4eab93763f"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../tuple.html"><tuple></a></span>
<span class="cp">#include <a href="../string.html"><string></a></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="c1">// 3要素のタプルを作る</span>
<span class="w"> </span><span class="n"><a href="">std::tuple</a></span><span class="o"><</span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="kt">char</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">></span><span class="w"> </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="make_tuple.html">std::make_tuple</a></span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="sc">'a'</span><span class="p">,</span><span class="w"> </span><span class="s">"hello"</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 0番目の要素を参照</span>
<span class="w"> </span><span class="kt">int</span><span class="o">&</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="tuple/get.html">std::get</a></span><span class="o"><</span><span class="mi">0</span><span class="o">></span><span class="p">(</span><span class="n">t</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">i</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="c1">// 2番目の要素を参照</span>
<span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">&</span><span class="w"> </span><span class="n">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="tuple/get.html">std::get</a></span><span class="o"><</span><span class="mi">2</span><span class="o">></span><span class="p">(</span><span class="n">t</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">s</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>
<h4>出力</h4>
<p><pre><code>1
hello
</code></pre></p>
<h3>基本的な使い方 (C++17)</h3>
<p><div class="yata" id="ee14232081b3b906eacf22ba5c3e3a62445b0e7e"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../tuple.html"><tuple></a></span>
<span class="cp">#include <a href="../string.html"><string></a></span>
<span class="c1">// 関数から複数の値を返す</span>
<span class="n"><a href="">std::tuple</a></span><span class="o"><</span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="kt">char</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">></span><span class="w"> </span><span class="n">f</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="c1">// <a href="make_tuple.html">std::make_tuple</a>()はほとんどの状況で必要ない</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="sc">'a'</span><span class="p">,</span><span class="w"> </span><span class="s">"hello"</span><span class="p">};</span>
<span class="p">}</span>
<span class="kt">int</span><span class="w"> </span><span class="n">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="c1">// 構造化束縛でタプルを分解して、それぞれの要素を代入</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">,</span><span class="w"> </span><span class="n">c</span><span class="p">]</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="n">a</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="n">b</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="n">c</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>
<h4>出力</h4>
<p><pre><code>1
a
hello
</code></pre></p>
<h3>プロキシ参照としての使い方（C++23）</h3>
<p>C++23 で<code><a href="../ranges/zip_view.html">zip_view</a></code>などが追加されたことに伴い、すべての要素がプロキシ参照であるような<code>tuple</code>は<a href="../iterator/indirectly_writable.html">プロキシ参照</a>として使用することが出来るようになった。</p>
<p><div class="yata" id="6df5b83a3e1e5e618524fd136245334be760d339"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../tuple.html"><tuple></a></span>
<span class="cp">#include <a href="../string_view.html"><string_view></a></span>
<span class="cp">#include <a href="../format.html"><format></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">A</span>
<span class="p">{</span>
<span class="w"> </span><span class="n">A</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">d</span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">i</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">d</span><span class="p">(</span><span class="n">d</span><span class="p">)</span>
<span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="n"><a href="">std::tuple</a></span><span class="o"><</span><span class="kt">int</span><span class="o">&</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="o">&></span><span class="w"> </span><span class="n">f</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// this が A* なので</span>
<span class="w"> </span><span class="c1">// i: int</span>
<span class="w"> </span><span class="c1">// d: double</span>
<span class="w"> </span><span class="c1">// ということと同じ</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">{</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">d</span><span class="p">};</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n"><a href="">std::tuple</a></span><span class="o"><</span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="o">&</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">double</span><span class="o">&></span><span class="w"> </span><span class="n">f</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="c1">// this が const A* なので</span>
<span class="w"> </span><span class="c1">// i: const int</span>
<span class="w"> </span><span class="c1">// d: const double</span>
<span class="w"> </span><span class="c1">// ということと同じ</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">{</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">d</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="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">d</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="c1">// プロキシ参照である <a href="">tuple</a> の性質</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">{</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mf">0.0</span><span class="p">};</span>
<span class="w"> </span><span class="c1">// <a href="">std::tuple</a><int&, double&></span>
<span class="w"> </span><span class="cm">/***/</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="cm">/***/</span><span class="w"> </span><span class="n">proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="c1">// const <a href="">std::tuple</a><int&, double&></span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">const_proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="c1">// <a href="">std::tuple</a><const int&, const double&></span>
<span class="w"> </span><span class="cm">/***/</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="cm">/***/</span><span class="w"> </span><span class="n">proxy_to_const</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">as_const</span><span class="p">(</span><span class="n">a</span><span class="p">).</span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="c1">// const <a href="">std::tuple</a><const int&, const double&></span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">const_proxy_to_const</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">as_const</span><span class="p">(</span><span class="n">a</span><span class="p">).</span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="c1">// OK（各要素が指すオブジェクトの値について、代入操作がなされる）</span>
<span class="w"> </span><span class="n">proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="n">const_proxy</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">f</span><span class="p">();</span>
<span class="w"> </span><span class="c1">// NG（各要素が指すオブジェクトを変更できない！）</span>
<span class="w"> </span><span class="c1">// proxy_to_const = a.f();</span>
<span class="w"> </span><span class="c1">// const_proxy_to_const = a.f();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// 使い方</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">print</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">[](</span><span class="n"><a href="../string_view/basic_string_view.html">std::string_view</a></span><span class="w"> </span><span class="n">prefix</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="o">&</span><span class="w"> </span><span class="n">a</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// 構造化束縛で分解</span>
<span class="w"> </span><span class="c1">// i: int&</span>
<span class="w"> </span><span class="c1">// d: double&</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="p">[</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">d</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span><span class="p">.</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="n">std</span><span class="o">::</span><span class="n">format</span><span class="p">(</span><span class="s">"{}: i={}, d={}</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span><span class="w"> </span><span class="n">prefix</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">d</span><span class="p">);</span>
<span class="w"> </span><span class="p">};</span>
<span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="n">a</span><span class="p">{</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mf">0.0</span><span class="p">},</span><span class="w"> </span><span class="n">b</span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mf">1.0</span><span class="p">};</span>
<span class="w"> </span><span class="n">print</span><span class="p">(</span><span class="s">"before a"</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">);</span>
<span class="w"> </span><span class="n">print</span><span class="p">(</span><span class="s">"before b"</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// プロキシ参照として使える <a href="">tuple</a> 同士の swap 操作で</span>
<span class="w"> </span><span class="c1">// 問題なく各要素が指す先のオブジェクトについて swap 操作が行える</span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ranges</span><span class="o">::</span><span class="n">swap</span><span class="p">(</span><span class="n">a</span><span class="p">.</span><span class="n">f</span><span class="p">(),</span><span class="w"> </span><span class="n">b</span><span class="p">.</span><span class="n">f</span><span class="p">());</span>
<span class="w"> </span><span class="n">print</span><span class="p">(</span><span class="s">"after a"</span><span class="p">,</span><span class="w"> </span><span class="n">a</span><span class="p">);</span>
<span class="w"> </span><span class="n">print</span><span class="p">(</span><span class="s">"after b"</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code>before a: i=0, d=0
before b: i=1, d=1
after a: i=1, d=1
after b: i=0, d=0
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++11</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: 3.0 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#gcc">GCC</a>: 4.3.4 <span aria-label="検証済" role="img" title="検証済">✅</span>, 4.4.4 <span aria-label="検証済" role="img" title="検証済">✅</span>, 4.5.2 <span aria-label="検証済" role="img" title="検証済">✅</span>, 4.6.1 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#icc">ICC</a>: ?</li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: 2008 <span aria-label="検証済" role="img" title="検証済">✅</span>, 2010 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
</ul>
<h2>関連項目</h2>
<ul>
<li><code><a href="../utility/pair.html">std::pair</a></code></li>
<li><a href="../../lang/cpp17/structured_bindings.html">C++17 構造化束縛</a></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://ja.wikipedia.org/wiki/%E3%82%BF%E3%83%97%E3%83%AB" target="_blank">タプル - Wikipedia</a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2321r2.html" target="_blank">P2321R2 <code>zip</code></a></li>
</ul></div>
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