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<header data-kunai-mdinfo="{&#34;meta&#34;: {&#34;header&#34;: [&#34;span&#34;], &#34;namespace&#34;: [&#34;std&#34;], &#34;id-type&#34;: [&#34;class template&#34;], &#34;cpp&#34;: [&#34;cpp20&#34;]}, &#34;sources&#34;: [{&#34;id&#34;: &#34;1c1514617d524e9e263396b695f419703b93ea43&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;span&gt;\n#include &lt;vector&gt;\n#include &lt;utility&gt;\n\n// \u30e1\u30e2\u30ea\u9023\u7d9a\u6027\u3092\u3082\u3064\u3042\u3089\u3086\u308b\u7bc4\u56f2\u3092\u51fa\u529b\u3059\u308b\u95a2\u6570\u3002\n// std::span\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306f\u30b3\u30d4\u30fc\u3067\u53d7\u3051\u53d6\u308b\u306e\u304c\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\ntemplate &lt;class T, std::size_t Extent&gt;\nvoid print(std::span&lt;T, Extent&gt; s)\n{\n  const char* delimiter = \&#34;\&#34;;\n\n  std::cout &lt;&lt; &#39;{&#39;;\n  for (const T&amp; x : s) {\n    std::cout &lt;&lt; std::exchange(delimiter, \&#34;,\&#34;) &lt;&lt; x;\n  }\n  std::cout &lt;&lt; &#39;}&#39; &lt;&lt; std::endl;\n}\n\nint main()\n{\n  std::vector&lt;int&gt; v = {1, 2, 3, 4, 5};\n  int ar[] = {1, 2, 3, 4, 5};\n\n  // span\u306b\u5909\u63db\u3057\u3066\u30b3\u30f3\u30c6\u30ca\u5168\u4f53\u3092\u51fa\u529b\n  print(std::span{v});\n\n  // \u30b3\u30f3\u30c6\u30ca\u306e\u4e00\u90e8\u306e\u8981\u7d20\u3092\u51fa\u529b\n  print(std::span{v}.subspan(1, 3));\n\n  // \u30dd\u30a4\u30f3\u30bf\u3068\u8981\u7d20\u6570\u3092\u6307\u5b9a\u3057\u305f\u7bc4\u56f2\u3092\u53c2\u7167\u3057\u3066\u3001\n  // \u7bc4\u56f2for\u6587\u3092\u4f7f\u7528\u3059\u308b\n  print(std::span&lt;int&gt;{ar, 3});\n}\n&#34;}, {&#34;id&#34;: &#34;51692b14f9ba98a4e9f5a59b321045957d16073f&#34;, &#34;source&#34;: &#34;#include &lt;iostream&gt;\n#include &lt;span&gt;\n#include &lt;vector&gt;\n#include &lt;utility&gt;\n\ntemplate &lt;class T&gt;\nvoid process_header(std::span&lt;T&gt; s)\n{\n  const char* delimiter = \&#34;\&#34;;\n\n  std::cout &lt;&lt; \&#34;[header] : \&#34;;\n  for (int x : s) {\n    std::cout &lt;&lt; std::exchange(delimiter, \&#34;,\&#34;) &lt;&lt; x;\n  }\n  std::cout &lt;&lt; std::endl;\n}\n\ntemplate &lt;class T&gt;\nvoid process_body(std::span&lt;T&gt; s)\n{\n  const char* delimiter = \&#34;\&#34;;\n\n  std::cout &lt;&lt; \&#34;[body] : \&#34;;\n  for (int x : s) {\n    std::cout &lt;&lt; std::exchange(delimiter, \&#34;,\&#34;) &lt;&lt; x;\n  }\n  std::cout &lt;&lt; std::endl;\n}\n\ntemplate &lt;class T&gt;\nvoid f(std::span&lt;T&gt; s)\n{\n  std::size_t header_size = 3;\n  process_header(s.first(header_size));\n  process_body(s.last(s.size() - header_size));\n}\n\nint main()\n{\n  std::vector&lt;int&gt; data = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};\n  f(std::span{data});\n}\n&#34;}], &#34;page_id&#34;: [&#34;reference&#34;, &#34;span&#34;, &#34;span&#34;]}">
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  <div class="identifier-type">class template</div><div class="header">&lt;span&gt;</div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">span</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="k">template</span><span class="w"> </span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">ElementType</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../cstddef/size_t.html">size_t</a></span><span class="w"> </span><span class="n">Extent</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="dynamic_extent.html">dynamic_extent</a></span><span class="o">&gt;</span>
<span class="w">  </span><span class="k">class</span><span class="w"> </span><span class="nc">span</span><span class="p">;</span>
<span class="w">  </span><span class="c1">// <a href="../ranges/view.html">view</a>コンセプトを有効化する</span>
<span class="w">  </span><span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">ElementType</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../cstddef/size_t.html">size_t</a></span><span class="w"> </span><span class="n">Extent</span><span class="o">&gt;</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="kt">bool</span><span class="w"> </span><span class="n">ranges</span><span class="o">::</span><span class="n"><a href="../ranges/enable_view.html">enable_view</a></span><span class="o">&lt;</span><span class="n">span</span><span class="o">&lt;</span><span class="n">ElementType</span><span class="p">,</span><span class="w"> </span><span class="n">Extent</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">true</span><span class="p">;</span>
<span class="w">  </span><span class="c1">// <a href="../ranges/borrowed_range.html">borrowed_range</a>コンセプトを有効化する</span>
<span class="w">  </span><span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">ElementType</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../cstddef/size_t.html">size_t</a></span><span class="w"> </span><span class="n">Extent</span><span class="o">&gt;</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="kt">bool</span><span class="w"> </span><span class="n">ranges</span><span class="o">::</span><span class="n"><a href="../ranges/enable_borrowed_range.html">enable_borrowed_range</a></span><span class="o">&lt;</span><span class="n">span</span><span class="o">&lt;</span><span class="n">ElementType</span><span class="p">,</span><span class="w"> </span><span class="n">Extent</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">true</span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
<h2>概要</h2>
<p><code>std::span</code>は、シーケンスの所有権を保持せず、部分シーケンスを参照するクラスである。</p>
<p>このクラスは、<code><a href="../vector/vector.html">std::vector</a></code>や配列といったコンテナから一部の連続的な要素を抽出し、それらの要素にのみなんらかの処理を適用する、という目的に使用できる。</p>
<p>文字列操作に特化したクラスとして<code><a href="../string_view/basic_string_view.html">std::basic_string_view</a></code>が定義されているが、こちらはメモリ連続性をもつあらゆるコンテナに適用できる。</p>
<p>このクラスは、<a href="../type_traits/is_trivially_copyable.html">トリビアルコピー可能</a>である（C++23）</p>
<h3>メモリ連続性</h3>
<p>このクラスの対象は、メモリの連続性を持つシーケンスである。例として、以下は対象のシーケンスである：</p>
<li>組み込み配列</li>
<li>要素を指すポインタと要素数の組</li>
<li>先頭要素を指すポインタと、末尾要素の次を指すポインタの組</li>
<li><code><a href="../array/array.html">std::array</a></code></li>
<li><code><a href="../vector/vector.html">std::vector</a></code></li>
<p>メモリ連続性をもつクラスは、非メンバ関数<code><a href="../iterator/data.html">data()</a></code>によってポインタを取得でき、非メンバ関数<code><a href="../iterator/size.html">size()</a></code>によって要素数を取得できること。それらの関数は、<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>によって呼び出される。</p>
<h3>静的な要素数と、動的な要素数</h3>
<p><code>std::span</code>は、静的な要素数をもつ場合と、動的な要素数をもつ場合の両方をサポートする。それはテンプレートパラメータ<code>Extent</code>によって表される。動的な要素数をもつ場合は、<code>Extent</code>として<code><a href="dynamic_extent.html">std::dynamic_extent</a></code>を指定する。動的な要素数は、<code><a href="../vector/vector.html">std::vector</a></code>を参照したり、ポインタと要素数の組を扱ったり、参照範囲を動的に変更したりする場合に必要となる。</p>
<p>静的な要素数をもつ場合、メンバ定数<code>extent</code>に要素数が保持されるため、メンバ変数として要素数を保持する必要がなく、領域を節約する最適化を行える。</p>
<h3><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Constraints。関数であればオーバーロード解決に参加するための条件、それ以外であれば受け付ける型の条件">テンプレートパラメータ制約</a></h3>
<li><code>ElementType</code>は、抽象型ではない完全オブジェクト型であること</li>
<h3>備考</h3>
<li><code>std::span</code>が参照する範囲<code>[s.<a href="span/data.html">data()</a>, s.<a href="span/data.html">data()</a> + s.<a href="span/size.html">size()</a>)</code>に含まれるポインタを無効にする操作を行った場合、<code>std::span</code>オブジェクトのメンバ関数から返されるその範囲のポインタ、イテレータ、<code>*this</code>以外の参照が無効になる</li>
<h2>メンバ関数</h2>
<h3>構築・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="span/op_constructor.html">(constructor)</a></code></td>
<td>コンストラクタ</td>
<td>C++20</td>
<td><code>~span() = default;</code></td>
<td>デストラクタ</td>
<td>C++20</td>
<td><code>span&amp; operator=(const span&amp;) = default;</code><br /> <code>span&amp; operator=(span&amp;&amp;) = default;</code></td>
<td>代入演算子</td>
<td>C++20</td>
<h3>サブシーケンスの参照</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="span/first.html">first</a></code></td>
<td>先頭N個の要素を参照する<code>span</code>オブジェクトを取得する</td>
<td>C++20</td>
<td><code><a href="span/last.html">last</a></code></td>
<td>末尾N個の要素を参照する<code>span</code>オブジェクトを取得する</td>
<td>C++20</td>
<td><code><a href="span/subspan.html">subspan</a></code></td>
<td>任意の位置からN個の要素を参照する<code>span</code>オブジェクトを取得する</td>
<td>C++20</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="span/size.html">size</a></code></td>
<td>参照している要素数を取得する</td>
<td>C++20</td>
<td><code><a href="span/size_bytes.html">size_bytes</a></code></td>
<td>参照している範囲のバイト数を取得する</td>
<td>C++20</td>
<td><code><a href="span/empty.html">empty</a></code></td>
<td>参照している範囲が空かどうかを判定する</td>
<td>C++20</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="span/op_at.html">operator[]</a></code></td>
<td>参照範囲から、任意の位置の要素を取得する</td>
<td>C++20</td>
<td><code><a href="span/at.html">at</a></code></td>
<td>参照範囲から、任意の位置の要素を取得する</td>
<td>C++26</td>
<td><code><a href="span/front.html">front</a></code></td>
<td>参照範囲の先頭要素を取得する</td>
<td>C++20</td>
<td><code><a href="span/back.html">back</a></code></td>
<td>参照範囲の末尾要素を取得する</td>
<td>C++20</td>
<td><code><a href="span/data.html">data</a></code></td>
<td>参照範囲の先頭を指すポインタを取得する</td>
<td>C++20</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="span/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++20</td>
<td><code><a href="span/end.html">end</a></code></td>
<td>末尾要素の次を指すイテレータを取得する</td>
<td>C++20</td>
<td><code><a href="span/rbegin.html">rbegin</a></code></td>
<td>末尾要素を指す逆順イテレータを取得する</td>
<td>C++20</td>
<td><code><a href="span/rend.html">rend</a></code></td>
<td>先頭要素の前を指す逆順イテレータを取得する</td>
<td>C++20</td>
<td><code><a href="span/cbegin.html">cbegin</a></code></td>
<td>先頭の要素を指す読み取り専用イテレータを取得する</td>
<td>C++23</td>
<td><code><a href="span/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++23</td>
<td><code><a href="span/crbegin.html">crbegin</a></code></td>
<td>末尾を指す読み取り専用逆イテレータを取得する</td>
<td>C++23</td>
<td><code><a href="span/crend.html">crend</a></code></td>
<td>先頭の前を指す読み取り専用逆イテレータを取得する</td>
<td>C++23</td>
<h3>メンバ定数</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>static constexpr size_type extent = Extent;</code></td>
<td>要素数。値が<code>-1</code>であれば動的な要素数、そうでなければ静的な固定要素数</td>
<td>C++20</td>
<h3>メンバ型</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>element_type</code></td>
<td>要素型 <code>ElementType</code></td>
<td>C++20</td>
<td><code>value_type</code></td>
<td><a class="cpprefjp-defined-word" data-desc="型をconstおよび・もしくはvolatileで修飾すること">CV修飾</a>を除いた要素型 <code><a href="../type_traits/remove_cv.html">remove_cv_t</a>&lt;ElementType&gt;</code></td>
<td>C++20</td>
<td><code>size_type</code></td>
<td>インデックスを表す符号なし整数型 <code><a href="../cstddef/size_t.html">size_t</a></code></td>
<td>C++20</td>
<td><code>difference_type</code></td>
<td>イテレータの差を表す符号付き整数型 <code><a href="../cstddef/ptrdiff_t.html">ptrdiff_t</a></code></td>
<td>C++20</td>
<td><code>pointer</code></td>
<td>ポインタ型 <code>element_type*</code></td>
<td>C++20</td>
<td><code>const_pointer</code></td>
<td><code>const</code>ポインタ型 <code>const element_type*</code></td>
<td>C++20</td>
<td><code>reference</code></td>
<td>参照型 <code>element_type&amp;</code></td>
<td>C++20</td>
<td><code>const_reference</code></td>
<td><code>const</code>参照型 <code>const element_type&amp;</code></td>
<td>C++20</td>
<td><code>iterator</code></td>
<td><a class="cpprefjp-defined-word" data-desc="処理系定義の動作。処理系によって事前に定めた動作をする" href="../../implementation-compliance.html#dfn-implementation-defined-behavior">実装定義</a>のイテレータ型。<code><a href="../iterator/contiguous_iterator.html">contiguous_iterator</a></code>、<code><a href="../iterator/random_access_iterator.html">random_access_iterator</a></code>、constexprイテレータのモデルであり、コンテナのイテレータに対するすべての要件を満たす</td>
<td>C++20</td>
<td><code>reverse_iterator</code></td>
<td>逆順イテレータ <code><a href="../iterator/reverse_iterator.html">reverse_iterator</a>&lt;iterator&gt;</code></td>
<td>C++20</td>
<td><code>const_iterator</code></td>
<td>読み取り専用イテレータ <code><a href="../iterator/const_iterator.html">std::const_iterator</a>&lt;iterator&gt;</code></td>
<td>C++23</td>
<td><code>const_reverse_iterator</code></td>
<td>読み取り専用逆イテレータ <code><a href="../iterator/const_iterator.html">std::const_iterator</a>&lt;reverse_iterator&gt;</code></td>
<td>C++23</td>
<h2>非メンバ関数</h2>
<h3>オブジェクトのバイト表現</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="span/as_bytes.html">as_bytes</a></code></td>
<td>読み取り専用バイト列としてシーケンスを参照する</td>
<td>C++20</td>
<td><code><a href="span/as_writable_bytes.html">as_writable_bytes</a></code></td>
<td>書込み可能なバイト列としてシーケンスを参照する</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="span/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++20</td>
<h3>基本的な使い方</h3>
<p><div class="yata" id="1c1514617d524e9e263396b695f419703b93ea43"><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="../span.html">&lt;span&gt;</a></span>
<span class="cp">#include <a href="../vector.html">&lt;vector&gt;</a></span>
<span class="cp">#include <a href="../utility.html">&lt;utility&gt;</a></span>
<span class="c1">// メモリ連続性をもつあらゆる範囲を出力する関数。</span>
<span class="c1">// <a href="">std::span</a>オブジェクトはコピーで受け取るのが基本的な使い方</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="n"><a href="../cstddef/size_t.html">std::size_t</a></span><span class="w"> </span><span class="n">Extent</span><span class="o">&gt;</span>
<span class="kt">void</span><span class="w"> </span><span class="n">print</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="o">&lt;</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">Extent</span><span class="o">&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">)</span>
<span class="p">{</span>
<span class="w">  </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">delimiter</span><span class="w"> </span><span class="o">=</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="sc">'{'</span><span class="p">;</span>
<span class="w">  </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">T</span><span class="o">&amp;</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">s</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"><a href="../utility/exchange.html">std::exchange</a></span><span class="p">(</span><span class="n">delimiter</span><span class="p">,</span><span class="w"> </span><span class="s">","</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</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="sc">'}'</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="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="n"><a href="../vector/vector.html">std::vector</a></span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">v</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="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">};</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">ar</span><span class="p">[]</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="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">};</span>
<span class="w">  </span><span class="c1">// spanに変換してコンテナ全体を出力</span>
<span class="w">  </span><span class="n">print</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="p">{</span><span class="n">v</span><span class="p">});</span>
<span class="w">  </span><span class="c1">// コンテナの一部の要素を出力</span>
<span class="w">  </span><span class="n">print</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="p">{</span><span class="n">v</span><span class="p">}.</span><span class="n"><a href="span/subspan.html">subspan</a></span><span class="p">(</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="c1">// ポインタと要素数を指定した範囲を参照して、</span>
<span class="w">  </span><span class="c1">// 範囲for文を使用する</span>
<span class="w">  </span><span class="n">print</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="p">{</span><span class="n">ar</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">});</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>{1,2,3,4,5}
</code></pre></p>
<h3>データのヘッダ情報とボディ情報をコピーなしで分割する</h3>
<p><div class="yata" id="51692b14f9ba98a4e9f5a59b321045957d16073f"><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="../span.html">&lt;span&gt;</a></span>
<span class="cp">#include <a href="../vector.html">&lt;vector&gt;</a></span>
<span class="cp">#include <a href="../utility.html">&lt;utility&gt;</a></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="kt">void</span><span class="w"> </span><span class="n">process_header</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">)</span>
<span class="p">{</span>
<span class="w">  </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">delimiter</span><span class="w"> </span><span class="o">=</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">"[header] : "</span><span class="p">;</span>
<span class="w">  </span><span class="k">for</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="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">s</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"><a href="../utility/exchange.html">std::exchange</a></span><span class="p">(</span><span class="n">delimiter</span><span class="p">,</span><span class="w"> </span><span class="s">","</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</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"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</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="kt">void</span><span class="w"> </span><span class="n">process_body</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">)</span>
<span class="p">{</span>
<span class="w">  </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">delimiter</span><span class="w"> </span><span class="o">=</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">"[body] : "</span><span class="p">;</span>
<span class="w">  </span><span class="k">for</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="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">s</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"><a href="../utility/exchange.html">std::exchange</a></span><span class="p">(</span><span class="n">delimiter</span><span class="p">,</span><span class="w"> </span><span class="s">","</span><span class="p">)</span><span class="w"> </span><span class="o">&lt;&lt;</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"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</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="kt">void</span><span class="w"> </span><span class="n">f</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="w"> </span><span class="n">s</span><span class="p">)</span>
<span class="p">{</span>
<span class="w">  </span><span class="n"><a href="../cstddef/size_t.html">std::size_t</a></span><span class="w"> </span><span class="n">header_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span>
<span class="w">  </span><span class="n">process_header</span><span class="p">(</span><span class="n"><a href="span/first.html">s.first</a></span><span class="p">(</span><span class="n">header_size</span><span class="p">));</span>
<span class="w">  </span><span class="n">process_body</span><span class="p">(</span><span class="n"><a href="span/last.html">s.last</a></span><span class="p">(</span><span class="n"><a href="span/size.html">s.size()</a></span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">header_size</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="n"><a href="../vector/vector.html">std::vector</a></span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">data</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="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">};</span>
<span class="w">  </span><span class="n">f</span><span class="p">(</span><span class="n"><a href="">std::span</a></span><span class="p">{</span><span class="n">data</span><span class="p">});</span>
<span class="p">}</span>
</code></pre></div>
<h4>出力</h4>
<p><pre><code>[header] : 1,2,3
[body] : 4,5,6,7,8,9,10
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<li>C++20</li>
<h3>処理系</h3>
<li><a href="../../implementation.html#clang">Clang</a>: 9.0 <span aria-label="検証済" role="img" title="検証済">✅</span></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>: 2019 Update 6 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<h2>参照</h2>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0122r7.pdf" target="_blank">P0122R7 <code>&lt;span&gt;</code> (n4740でwording changeあり)</a><ul>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/n4740.html" target="_blank">N4740 2018年03月 Jacksonville会議</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1085r2.md" target="_blank">P1085R2 Should <code>span</code> be regular?</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1227r2.html" target="_blank">P1227R2 Signed <code>ssize()</code> functions, unsigned <code>size()</code> functions</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1024r3.pdf" target="_blank">P1024R3 Usability enhancements for <code>std::span</code></a></li>
<li><a href="https://wg21.cmeerw.net/lwg/issue3102" target="_blank">LWG Issue 3102 Clarify <code>span iterator</code> and <code>const_iterator</code> behavior</a></li>
<li><a href="https://wg21.cmeerw.net/lwg/issue3144" target="_blank">LWG Issue 3144. <code>span</code> does not have a <code>const_pointer</code> typedef</a></li>
<li><a href="https://cplusplus.github.io/LWG/lwg-active.html#3203" target="_blank">LWG Issue 3203. <code>span</code> element access invalidation</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1872r0.pdf" target="_blank">P1872R0 <code>span</code> should have <code>size_type</code>, not <code>index_type</code></a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2051r0.html" target="_blank">P2051R0 C++ Standard Library Issues to be moved in Prague</a><ul>
<li><code>const_iterator</code>, <code>const_reverse_iterator</code>, <code>cbegin()</code>, <code>cend()</code>, <code>crbegin()</code>, <code>crend()</code>を削除</li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2116r0.html" target="_blank">P2116R0 Remove tuple-like protocol support from fixed-extent <code>span</code></a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0896r4.pdf" target="_blank">P0896R4 The One Ranges Proposal (was Merging the Ranges TS)</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2325r3.html" target="_blank">P2325R3 Views should not be required to be default constructible</a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2251r1.pdf" target="_blank">Require <code>span</code> &amp; <code>basic_string_view</code> to be Trivially Copyable</a><ul>
<li>C++23から、トリビアルコピー可能が保証される。</li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2278r4.html" target="_blank">P2278R4 <code>cbegin</code> should always return a constant iterator</a></li>
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