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<header data-kunai-mdinfo="{&#34;meta&#34;: {&#34;header&#34;: [&#34;forward_list&#34;], &#34;namespace&#34;: [&#34;std&#34;], &#34;id-type&#34;: [&#34;class template&#34;], &#34;cpp&#34;: [&#34;cpp11&#34;]}, &#34;sources&#34;: [{&#34;id&#34;: &#34;62631f4cc139fe002cfd3f94e70c19fff00e1291&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;forward_list&gt;\n#include &lt;algorithm&gt;\n#include &lt;utility&gt;\n\nint main()\n{\n  std::forward_list&lt;int&gt; ls;\n\n  ls.push_front(3);               // \u5148\u982d\u306b3\u3092\u8ffd\u52a0\n  ls.insert_after(ls.begin(), 1); // \u5148\u982d\u306e\u5f8c\u308d\u306b1\u3092\u8ffd\u52a0\n\n  // \u30a4\u30c6\u30ec\u30fc\u30bf\u3092\u4ecb\u3057\u3066\u5168\u8981\u7d20\u306b\u5bfe\u3057\u3066\u64cd\u4f5c\u3092\u884c\u3046\n  std::for_each(ls.cbegin(), ls.cend(), [](int x) {\n    std::cout &lt;&lt; x &lt;&lt; std::endl;\n  });\n}\n&#34;}, {&#34;id&#34;: &#34;a4992378a5813cdccb5749675c968b78ed0de5fe&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;forward_list&gt;\n#include &lt;string&gt;\n#include &lt;utility&gt;\n\n//\u7c21\u6613\u306a\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u69cb\u9020\u8868\u73fe\u30af\u30e9\u30b9\n//forward_list\u306e\u7279\u6027\u4e0a\u51fa\u529b\u304c\u9006\u9806\u306b\u306a\u308b\nclass directory {\n\n  //\u4e0d\u5b8c\u5168\u578b\uff08\u30af\u30e9\u30b9\u5b9a\u7fa9\u5185\u3067\u306f\u305d\u306e\u30af\u30e9\u30b9\u81ea\u8eab\u306f\u4e0d\u5b8c\u5168\uff09\u3092\u8981\u7d20\u578b\u306b\u6307\u5b9a\n  std::forward_list&lt;directory&gt; m_subdir{};\n  std::string m_name{};\n\npublic:\n\n  directory(const char* name) : m_name{name}\n  {}\n\n  //\u30b5\u30d6\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u8ffd\u52a0\n  template&lt;typename Dir&gt;\n  void add(Dir&amp;&amp; dir) {\n    m_subdir.emplace_front(std::forward&lt;Dir&gt;(dir));\n  }\n\n  //\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u540d\u53d6\u5f97\n  auto get() const -&gt; const std::string&amp; {\n    return m_name;\n  }\n\n  auto begin() const {\n    return m_subdir.begin();\n  }\n\n  auto end() const {\n    return m_subdir.end();\n  }\n};\n\n//\u30eb\u30fc\u30c8\u3088\u308a\u4e0b\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b\u3064\u3044\u3066\u6574\u5f62\u3057\u3066\u51fa\u529b\nvoid recursive_out(const directory&amp; dir, unsigned int depth) {\n\n  if (1 &lt; depth) std::cout &lt;&lt; \&#34;| \&#34;;\n  for (auto i = depth; 2 &lt; i; --i) {\n    std::cout &lt;&lt; \&#34; \&#34;;\n  }\n  if (2 &lt; depth) std::cout &lt;&lt; \&#34; \&#34;;\n\n  std::cout &lt;&lt; \&#34;|-\&#34; &lt;&lt; dir.get() &lt;&lt; std::endl;\n\n  for (auto&amp; subdir : dir) {\n    recursive_out(subdir, depth + 1);\n  }\n}\n\n//\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u69cb\u9020\u3092\u51fa\u529b\u3059\u308b\nvoid out_directorytree(const directory&amp; dir) {\n  std::cout &lt;&lt; dir.get() &lt;&lt; std::endl;\n\n  for (auto&amp; subdir : dir) {\n    recursive_out(subdir, 1);\n  }\n}\n\nint main() {\n  directory dir{\&#34;root\&#34;};\n  dir.add(\&#34;sub1\&#34;);\n\n  directory sub2{\&#34;sub2\&#34;};\n  sub2.add(\&#34;sub2.1\&#34;);\n\n  directory sub22{\&#34;sub2.2\&#34;};\n  sub22.add(\&#34;sub2.2.1\&#34;);\n\n  sub2.add(std::move(sub22));\n\n  dir.add(std::move(sub2));\n  dir.add(\&#34;sub3\&#34;);\n\n  out_directorytree(dir);\n}\n&#34;}], &#34;page_id&#34;: [&#34;reference&#34;, &#34;forward_list&#34;, &#34;forward_list&#34;]}">
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  <div class="identifier-type">class template</div><div class="header">&lt;forward_list&gt;</div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">forward_list</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">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../memory/allocator.html">allocator</a></span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;&gt;</span>
<span class="w">  </span><span class="k">class</span><span class="w"> </span><span class="nc">forward_list</span><span class="p">;</span>
<span class="w">  </span><span class="k">namespace</span><span class="w"> </span><span class="nn">pmr</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">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">&gt;</span>
<span class="w">      </span><span class="k">using</span><span class="w"> </span><span class="n">forward_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="">std::forward_list</a></span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../memory_resource/polymorphic_allocator.html">polymorphic_allocator</a></span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;&gt;</span><span class="p">;</span><span class="w">  </span><span class="c1">// C++17から</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
<h2>概要</h2>
<p><code>forward_list</code>は、単方向リンクリストのデータ構造をもつクラスである。</p>
<p><code>forward_list</code>は、標準ライブラリではシーケンスコンテナの一種として定義されるが、いくつかの点でシーケンスコンテナの要件を満たさない：</p>
<p><code>size()</code>メンバ関数を提供しない。</p>
<li><code>size()</code>メンバ関数は全てのコンテナにO(1)<a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Complexity。関数が使うアルゴリズムの空間計算量・時間計算量">計算量</a>を要求するため、単方向リストの実装ではサイズのためのメンバ変数が必要になる。<code>forward_list</code>では、サイズメンバ変数を内部に持たないことを示すために<code>size()</code>メンバ関数は提供しない。要素数が必要な場合は<code><a href="../iterator/distance.html">distance()</a></code>を使用して取得する。</li>
<p><code>insert()/emplace()/erase()</code>メンバ関数を提供しない。</p>
<li>双方向リンクリストである<code><a href="../list/list.html">list</a></code>の<code><a href="../list/list/insert.html">insert()</a></code>／<code><a href="../list/list/emplace.html">emplace()</a></code>／<code><a href="../list/list/erase.html">erase()</a></code>はinsert-before方式をとっておりO(1)<a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Complexity。関数が使うアルゴリズムの空間計算量・時間計算量">計算量</a>だが、単方向リストの典型的なinsert-beforeの実装ではO(N)<a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Complexity。関数が使うアルゴリズムの空間計算量・時間計算量">計算量</a>になってしまう。</li>
<li><code>forward_list</code>では、単方向リンクリストでO(1)<a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Complexity。関数が使うアルゴリズムの空間計算量・時間計算量">計算量</a>であるinsert-after方式を使用することを示す<code><a href="forward_list/insert_after.html">insert_after()</a></code>／<code><a href="forward_list/emplace_after.html">emplace_after()</a></code>／<code><a href="forward_list/erase_after.html">erase_after()</a></code>メンバ関数を提供する。先頭に挿入するために<code><a href="forward_list/before_begin.html">before_begin()</a></code>メンバ関数を提供する。</li>
<p><code>forward_list</code>は、C言語で単方向リンクリストを実装する場合と比べ、空間的にもパフォーマンス的にもゼロオーバーヘッドであるよう設計されている。<br />
また、<code>forward_list</code>はリンクリストの性質上、挿入・削除のような破壊的操作を行なってもイテレータは無効にならない。</p>
<p>各テンプレートパラメータの意味は次の通りである。</p>
<li><code>T</code>: 格納される要素の型、C++17以降は<a class="cpprefjp-defined-word" data-desc="型のサイズを決定できない、完全には定義されていない型。例えば先行宣言のみのクラス型、要素数不明の配列型、`void`など。クラス定義内部ではそのクラス自身は不完全型">不完全型</a>をサポートしている</li>
<li><code>Allocator</code>: メモリ確保に使用されるアロケータの型。無指定の場合は標準の<code><a href="../memory/allocator.html">allocator</a></code>クラスが使用される。</li>
<h2>メンバ関数</h2>
<h3>構築／コピー／破棄</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/op_constructor.html">(constructor)</a></code></td>
<td>コンストラクタ</td>
<td>C++11</td>
<td><code><a href="forward_list/op_destructor.html">(destructor)</a></code></td>
<td>デストラクタ</td>
<td>C++11</td>
<td><code><a href="forward_list/op_assign.html">operator=</a></code></td>
<td>代入演算子</td>
<td>C++11</td>
<td><code><a href="forward_list/assign.html">assign</a></code></td>
<td>コンテナの再代入</td>
<td>C++11</td>
<td><code><a href="forward_list/assign_range.html">assign_range</a></code></td>
<td>Rangeの要素を再代入</td>
<td>C++23</td>
<h3>イテレータ</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/before_begin.html">before_begin</a></code></td>
<td>先頭要素の前を指すイテレータを取得する</td>
<td>C++11</td>
<td><code><a href="forward_list/begin.html">begin</a></code></td>
<td>先頭要素を指すイテレータを取得する</td>
<td>C++11</td>
<td><code><a href="forward_list/end.html">end</a></code></td>
<td>末尾の次を指すイテレータを取得する</td>
<td>C++11</td>
<td><code><a href="forward_list/cbegin.html">cbegin</a></code></td>
<td>先頭要素を指す読み取り専用イテレータを取得する</td>
<td>C++11</td>
<td><code><a href="forward_list/cbefore_begin.html">cbefore_begin</a></code></td>
<td>先頭要素の前を指す読み取り専用イテレータを取得する</td>
<td>C++11</td>
<td><code><a href="forward_list/cend.html">cend</a></code></td>
<td>末尾の次を指す読み取り専用イテレータを取得する</td>
<td>C++11</td>
<h3>領域</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/empty.html">empty</a></code></td>
<td>コンテナが空かどうかを判定する</td>
<td>C++11</td>
<td><code><a href="forward_list/max_size.html">max_size</a></code></td>
<td>格納可能な最大の要素数を取得する</td>
<td>C++11</td>
<h3>要素アクセス</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/front.html">front</a></code></td>
<td>先頭要素への参照を取得する</td>
<td>C++11</td>
<h3>コンテナの変更</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/emplace_front.html">emplace_front</a></code></td>
<td>先頭への直接構築による要素追加</td>
<td>C++11</td>
<td><code><a href="forward_list/push_front.html">push_front</a></code></td>
<td>先頭に要素を追加する</td>
<td>C++11</td>
<td><code><a href="forward_list/prepend_range.html">prepend_range</a></code></td>
<td>先頭にRangeの要素を追加する</td>
<td>C++23</td>
<td><code><a href="forward_list/pop_front.html">pop_front</a></code></td>
<td>先頭から要素を削除</td>
<td>C++11</td>
<td><code><a href="forward_list/emplace_after.html">emplace_after</a></code></td>
<td>任意の位置への直接構築による要素挿入</td>
<td>C++11</td>
<td><code><a href="forward_list/insert_after.html">insert_after</a></code></td>
<td>任意の位置への要素挿入</td>
<td>C++11</td>
<td><code><a href="forward_list/insert_range_after.html">insert_range_after</a></code></td>
<td>任意の位置へRangeの要素挿入</td>
<td>C++23</td>
<td><code><a href="forward_list/erase_after.html">erase_after</a></code></td>
<td>指定したイテレータの次の要素を削除する</td>
<td>C++11</td>
<td><code><a href="forward_list/swap.html">swap</a></code></td>
<td>コンテナの交換</td>
<td>C++11</td>
<td><code><a href="forward_list/resize.html">resize</a></code></td>
<td>要素数を変更する</td>
<td>C++11</td>
<td><code><a href="forward_list/clear.html">clear</a></code></td>
<td>全要素削除</td>
<td>C++11</td>
<h3>単方向リスト操作</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/splice_after.html">splice_after</a></code></td>
<td>他のコンテナから要素を移動する</td>
<td>C++11</td>
<td><code><a href="forward_list/remove.html">remove</a></code></td>
<td>コンテナから指定された値の要素を削除する</td>
<td>C++11</td>
<td><code><a href="forward_list/remove_if.html">remove_if</a></code></td>
<td>コンテナから条件に合った要素を削除する</td>
<td>C++11</td>
<td><code><a href="forward_list/unique.html">unique</a></code></td>
<td>重複した要素をコンテナから削除する</td>
<td>C++11</td>
<td><code><a href="forward_list/merge.html">merge</a></code></td>
<td>2つのコンテナを併合する</td>
<td>C++11</td>
<td><code><a href="forward_list/sort.html">sort</a></code></td>
<td>コンテナを並べ替える</td>
<td>C++11</td>
<td><code><a href="forward_list/reverse.html">reverse</a></code></td>
<td>コンテナを反転する</td>
<td>C++11</td>
<h3>アロケータ</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/get_allocator.html">get_allocator</a></code></td>
<td>アロケータオブジェクトの取得</td>
<td>C++11</td>
<h2>メンバ型</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code>reference</code></td>
<td><code>T&amp;</code></td>
<td>C++11</td>
<td><code>const_reference</code></td>
<td><code>const T&amp;</code></td>
<td>C++11</td>
<td><code>iterator</code></td>
<td>前方向イテレータ</td>
<td>C++11</td>
<td><code>const_iterator</code></td>
<td>読み取り専用前方向イテレータ</td>
<td>C++11</td>
<td><code>size_type</code></td>
<td>符号なし整数型(通常は<code><a href="../cstddef/size_t.html">size_t</a></code>)</td>
<td>C++11</td>
<td><code>difference_type</code></td>
<td>符号付き整数型(通常は<code><a href="../cstddef/ptrdiff_t.html">ptrdiff_t</a></code>)</td>
<td>C++11</td>
<td><code>value_type</code></td>
<td><code>T</code></td>
<td>C++11</td>
<td><code>allocator_type</code></td>
<td><code>Allocator</code></td>
<td>C++11</td>
<td><code>pointer</code></td>
<td><code><a href="../memory/allocator_traits.html">allocator_traits</a>&lt;Allocator&gt;::pointer</code></td>
<td>C++11</td>
<td><code>const_pointer</code></td>
<td><code><a href="../memory/allocator_traits.html">allocator_traits</a>&lt;Allocator&gt;::const_pointer</code></td>
<td>C++11</td>
<h2>非メンバ関数</h2>
<h3>比較演算子</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/op_equal.html">operator==</a></code></td>
<td>等値比較</td>
<td>C++11</td>
<td><code><a href="forward_list/op_not_equal.html">operator!=</a></code></td>
<td>非等値比較</td>
<td>C++11</td>
<td><code><a href="forward_list/op_compare_3way.html">operator&lt;=&gt;</a></code></td>
<td>三方比較</td>
<td>C++20</td>
<td><code><a href="forward_list/op_less.html">operator&lt;</a></code></td>
<td>左辺が右辺より小さいかの判定を行う</td>
<td>C++11</td>
<td><code><a href="forward_list/op_less_equal.html">operator&lt;=</a></code></td>
<td>左辺が右辺以下かの判定を行う</td>
<td>C++11</td>
<td><code><a href="forward_list/op_greater.html">operator&gt;</a></code></td>
<td>左辺が右辺より大きいかの判定を行う</td>
<td>C++11</td>
<td><code><a href="forward_list/op_greater_equal.html">operator&gt;=</a></code></td>
<td>左辺が右辺以上かの判定を行う</td>
<td>C++11</td>
<h3>入れ替え</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/swap_free.html">swap</a></code></td>
<td>2つの<code>forward_list</code>オブジェクトを入れ替える</td>
<td>C++11</td>
<h3>要素削除</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/erase_free.html">erase</a></code></td>
<td>指定した値をもつ要素とその分の領域を、コンテナから削除する</td>
<td>C++20</td>
<td><code><a href="forward_list/erase_if_free.html">erase_if</a></code></td>
<td>指定した条件に合致する要素とその分の領域を、コンテナから削除する</td>
<td>C++20</td>
<h2>推論補助</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
<td><code><a href="forward_list/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>
<h3>基本的な使い方</h3>
<p><div class="yata" id="62631f4cc139fe002cfd3f94e70c19fff00e1291"><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="../forward_list.html">&lt;forward_list&gt;</a></span>
<span class="cp">#include <a href="../algorithm.html">&lt;algorithm&gt;</a></span>
<span class="cp">#include <a href="../utility.html">&lt;utility&gt;</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="n"><span style="color:#ff0000">std::forward_list</span></span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">ls</span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="forward_list/push_front.html">ls.push_front</a></span><span class="p">(</span><span class="mi">3</span><span class="p">);</span><span class="w">               </span><span class="c1">// 先頭に3を追加</span>
<span class="w">  </span><span class="n"><a href="forward_list/insert_after.html">ls.insert_after</a></span><span class="p">(</span><span class="n"><a href="forward_list/begin.html">ls.begin()</a></span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// 先頭の後ろに1を追加</span>
<span class="w">  </span><span class="c1">// イテレータを介して全要素に対して操作を行う</span>
<span class="w">  </span><span class="n"><a href="../algorithm/for_each.html">std::for_each</a></span><span class="p">(</span><span class="n"><a href="forward_list/cbegin.html">ls.cbegin()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="forward_list/cend.html">ls.cend()</a></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">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="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>3
</code></pre></p>
<h3><a class="cpprefjp-defined-word" data-desc="型のサイズを決定できない、完全には定義されていない型。例えば先行宣言のみのクラス型、要素数不明の配列型、`void`など。クラス定義内部ではそのクラス自身は不完全型">不完全型</a>を要素にする例 (C++17)</h3>
<p><a class="cpprefjp-defined-word" data-desc="型のサイズを決定できない、完全には定義されていない型。例えば先行宣言のみのクラス型、要素数不明の配列型、`void`など。クラス定義内部ではそのクラス自身は不完全型">不完全型</a>を要素型に出来るようになった事で、階層構造や多分木などの再帰的データ構造を実装することが容易になる。<br />
他にも、<code><a href="../vector/vector.html">vector</a></code>と<code><a href="../list/list.html">list</a></code>が<a class="cpprefjp-defined-word" data-desc="型のサイズを決定できない、完全には定義されていない型。例えば先行宣言のみのクラス型、要素数不明の配列型、`void`など。クラス定義内部ではそのクラス自身は不完全型">不完全型</a>をサポートしている。</p>
<p><div class="yata" id="a4992378a5813cdccb5749675c968b78ed0de5fe"><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="../forward_list.html">&lt;forward_list&gt;</a></span>
<span class="cp">#include <a href="../string.html">&lt;string&gt;</a></span>
<span class="cp">#include <a href="../utility.html">&lt;utility&gt;</a></span>
<span class="c1">//簡易なディレクトリ構造表現クラス</span>
<span class="c1">//forward_listの特性上出力が逆順になる</span>
<span class="k">class</span><span class="w"> </span><span class="nc">directory</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="c1">//不完全型（クラス定義内ではそのクラス自身は不完全）を要素型に指定</span>
<span class="w">  </span><span class="n"><span style="color:#ff0000">std::forward_list</span></span><span class="o">&lt;</span><span class="n">directory</span><span class="o">&gt;</span><span class="w"> </span><span class="n">m_subdir</span><span class="p">{};</span>
<span class="w">  </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">m_name</span><span class="p">{};</span>
<span class="k">public</span><span class="o">:</span>
<span class="w">  </span><span class="n">directory</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">m_name</span><span class="p">{</span><span class="n">name</span><span class="p">}</span>
<span class="w">  </span><span class="p">{}</span>
<span class="w">  </span><span class="c1">//サブディレクトリ追加</span>
<span class="w">  </span><span class="k">template</span><span class="o">&lt;</span><span class="k">typename</span><span class="w"> </span><span class="nc">Dir</span><span class="o">&gt;</span>
<span class="w">  </span><span class="kt">void</span><span class="w"> </span><span class="n">add</span><span class="p">(</span><span class="n">Dir</span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">dir</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n">m_subdir</span><span class="p">.</span><span class="n"><a href="forward_list/emplace_front.html">emplace_front</a></span><span class="p">(</span><span class="n"><a href="../utility/forward.html">std::forward</a></span><span class="o">&lt;</span><span class="n">Dir</span><span class="o">&gt;</span><span class="p">(</span><span class="n">dir</span><span class="p">));</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="c1">//ディレクトリ名取得</span>
<span class="w">  </span><span class="k">auto</span><span class="w"> </span><span class="n">get</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="o">-&gt;</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">&amp;</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">m_name</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"><a href="forward_list/begin.html">begin</a></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">m_subdir</span><span class="p">.</span><span class="n"><a href="forward_list/begin.html">begin</a></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"><a href="forward_list/end.html">end</a></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">m_subdir</span><span class="p">.</span><span class="n"><a href="forward_list/end.html">end</a></span><span class="p">();</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">};</span>
<span class="c1">//ルートより下のディレクトリについて整形して出力</span>
<span class="kt">void</span><span class="w"> </span><span class="nf">recursive_out</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">directory</span><span class="o">&amp;</span><span class="w"> </span><span class="n">dir</span><span class="p">,</span><span class="w"> </span><span class="kt">unsigned</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">depth</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">depth</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="s">"| "</span><span class="p">;</span>
<span class="w">  </span><span class="n"><a href="../../lang/cpp11/range_based_for.html">for</a></span><span class="w"> </span><span class="p">(</span><span class="k">auto</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">depth</span><span class="p">;</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">i</span><span class="p">;</span><span class="w"> </span><span class="o">--</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"><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="s">" "</span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>
<span class="w">  </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">depth</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="s">" "</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="s">"|-"</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">dir</span><span class="p">.</span><span class="n">get</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="n"><a href="../../lang/cpp11/range_based_for.html">for</a></span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="o">&amp;</span><span class="w"> </span><span class="n">subdir</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">dir</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n">recursive_out</span><span class="p">(</span><span class="n">subdir</span><span class="p">,</span><span class="w"> </span><span class="n">depth</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span>
<span class="w">  </span><span class="p">}</span>
<span class="p">}</span>
<span class="c1">//ディレクトリ構造を出力する</span>
<span class="kt">void</span><span class="w"> </span><span class="nf">out_directorytree</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">directory</span><span class="o">&amp;</span><span class="w"> </span><span class="n">dir</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">dir</span><span class="p">.</span><span class="n">get</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="n"><a href="../../lang/cpp11/range_based_for.html">for</a></span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="o">&amp;</span><span class="w"> </span><span class="n">subdir</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">dir</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w">    </span><span class="n">recursive_out</span><span class="p">(</span><span class="n">subdir</span><span class="p">,</span><span class="w"> </span><span class="mi">1</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="w"> </span><span class="p">{</span>
<span class="w">  </span><span class="n">directory</span><span class="w"> </span><span class="n">dir</span><span class="p">{</span><span class="s">"root"</span><span class="p">};</span>
<span class="w">  </span><span class="n">dir</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="s">"sub1"</span><span class="p">);</span>
<span class="w">  </span><span class="n">directory</span><span class="w"> </span><span class="n">sub2</span><span class="p">{</span><span class="s">"sub2"</span><span class="p">};</span>
<span class="w">  </span><span class="n">sub2</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="s">"sub2.1"</span><span class="p">);</span>
<span class="w">  </span><span class="n">directory</span><span class="w"> </span><span class="n">sub22</span><span class="p">{</span><span class="s">"sub2.2"</span><span class="p">};</span>
<span class="w">  </span><span class="n">sub22</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="s">"sub2.2.1"</span><span class="p">);</span>
<span class="w">  </span><span class="n">sub2</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="n"><a href="../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">sub22</span><span class="p">));</span>
<span class="w">  </span><span class="n">dir</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="n"><a href="../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">sub2</span><span class="p">));</span>
<span class="w">  </span><span class="n">dir</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="s">"sub3"</span><span class="p">);</span>
<span class="w">  </span><span class="n">out_directorytree</span><span class="p">(</span><span class="n">dir</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>root
|   |-sub2.2.1
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<li>C++11</li>
<h3>処理系</h3>
<li><a href="../../implementation.html#clang">Clang</a>: ??</li>
<li><a href="../../implementation.html#gcc">GCC</a>: 4.7.0 <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>: ??</li>
<h2>参照</h2>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2543.htm" target="_blank">N2543 STL singly linked lists (revision 3)</a> [<a href="http://faithandbrave.hateblo.jp/entry/20080905/1220611240" target="_blank">概要の日本語訳</a>]</li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4510.html" target="_blank">N4510 Minimal incomplete type support for standard containers, revision 4</a></li>
</ul></div>
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