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<header data-kunai-mdinfo="{"meta": {"header": ["mdspan"], "id-type": ["function template"], "namespace": ["std"], "cpp": ["cpp26"]}, "sources": [{"id": "e0290321d286586529963e74c83e922689ccd679", "source": "#include <mdspan>\n#include <numeric>\n#include <print>\n#include <string_view>\n#include <utility>\n\n// 2\u6b21\u5143\u914d\u5217\u30d3\u30e5\u30fc(Matrix)\u306e\u8981\u7d20\u8868\u793a\ntemplate <class T, class E, class L, class A>\nvoid print_mat(std::string_view name, const std::mdspan<T, E, L, A>& mat)\n{\n static_assert(mat.rank() == 2);\n std::println(\"{}:\", name);\n for (size_t i = 0; i < mat.extent(0); ++i) {\n for (size_t j = 0; j < mat.extent(1); ++j) {\n std::print(\" {:2}\", mat[i, j]);\n }\n std::println(\"\");\n }\n}\n\n// 1\u6b21\u5143\u914d\u5217\u30d3\u30e5\u30fc(Vector)\u306e\u8981\u7d20\u8868\u793a\ntemplate <class T, class E, class L, class A>\nvoid print_vec(std::string_view name, const std::mdspan<T, E, L, A>& mat)\n{\n static_assert(mat.rank() == 1);\n std::println(\"{}:\", name);\n for (size_t i = 0; i < mat.extent(0); ++i) {\n std::print(\" {:2}\", mat[i]);\n }\n std::println(\"\");\n}\n\nint main()\n{\n int arr[20];\n std::ranges::iota(arr, 1);\n\n // 4x5\u8981\u7d20\u306e2\u6b21\u5143\u914d\u5217\u30d3\u30e5\u30fc\n using Ext2D = std::dextents<size_t, 2>;\n std::mdspan mat{arr, Ext2D{4, 5}};\n print_mat(\"mat\", mat);\n\n // \u30a4\u30f3\u30c7\u30af\u30b9\u5024\u6307\u5b9a\uff0b\u5168\u8981\u7d20\u6307\u5b9a\uff082\u6b21\u5143\u21921\u6b21\u5143\uff09\n auto row1 = std::submdspan(mat, 1, std::full_extent);\n print_vec(\"mat[1,M]\", row1);\n auto col2 = std::submdspan(mat, std::full_extent, 2);\n print_vec(\"mat[N,2]\", col2);\n\n // \u5358\u4e00\u8981\u7d20\u306e\u53d6\u308a\u51fa\u3057\uff082\u6b21\u5143\u21920\u6b21\u5143\uff09\n auto elem = std::submdspan(mat, 1, 2);\n std::println(\"mat[1,2]:\\n {:2}\", elem[]);\n\n // \u30a4\u30f3\u30c7\u30af\u30b9\u7bc4\u56f2\u6307\u5b9a\n auto submat = std::submdspan(mat, std::pair{1,3}, std::pair{1,4});\n print_mat(\"submat\", submat);\n\n // \u30b9\u30c8\u30e9\u30a4\u30c9\u30fb\u30b9\u30e9\u30a4\u30b9\u6307\u5b9a\n auto strided = std::submdspan(mat,\n std::strided_slice{.offset=1, .extent=3, .stride=2}, \n std::strided_slice{.offset=0, .extent=5, .stride=2});\n print_mat(\"strided\", strided);\n}\n"}, {"id": "154d20bbd1a205c8572508587ad781937b65c78d", "source": "#include <concepts>\n#include <mdspan>\n#include <numeric>\n#include <print>\n#include <utility>\n\n// \u6574\u6570\u5b9a\u6570\u578b\ntemplate <int N>\nconstexpr auto Int = std::integral_constant<int, N>{};\n\nint main()\n{\n int arr[20];\n std::ranges::iota(arr, 1);\n\n // \u9759\u7684\u8981\u7d20\u6570 4x5 \u306e2\u6b21\u5143\u914d\u5217\u30d3\u30e5\u30fc\n std::mdspan mat{arr, std::extents<size_t, 4, 5>{}};\n\n // \u52d5\u7684\u8981\u7d20\u6570 2x3 \u306e2\u6b21\u5143\u914d\u5217\u90e8\u5206\u30d3\u30e5\u30fc\u3092\u53d6\u308a\u51fa\u3057\n auto submat_dyn = std::submdspan(mat,\n std::pair{1, 3},\n std::strided_slice{.offset=0, .extent=5, .stride=2});\n static_assert(std::same_as<decltype(submat_dyn)::extents_type, std::dextents<size_t, 2>>);\n std::println(\"submat_dyn {}x{}\", submat_dyn.extent(0), submat_dyn.extent(1));\n\n // \u9759\u7684\u8981\u7d20\u6570 2x3 \u306e2\u6b21\u5143\u914d\u5217\u90e8\u5206\u30d3\u30e5\u30fc\u3092\u53d6\u308a\u51fa\u3057\n auto submat_2x3 = std::submdspan(mat,\n std::pair{Int<1>, Int<3>},\n std::strided_slice{.offset=0, .extent=Int<5>, .stride=Int<2>});\n // (strided_slice::offset \u306f\u623b\u308a\u5024\u578b\u306b\u5f71\u97ff\u3092\u4e0e\u3048\u306a\u3044)\n static_assert(std::same_as<decltype(submat_2x3)::extents_type, std::extents<size_t, 2, 3>>);\n std::println(\"submat_2x3 {}x{}\", submat_2x3.extent(0), submat_2x3.extent(1));\n}\n"}, {"id": "4a6f4af3a755612953df799a2870a4ab692364db", "source": "#include <mdspan>\n#include <utility>\n\nint main()\n{\n int arr[6] = {1, 2, 3, 4, 5, 6};\n\n // 3x2\u8981\u7d20\u306e2\u6b21\u5143\u914d\u5217\u30d3\u30e5\u30fc\uff08\u884c\u512a\u5148\u30ec\u30a4\u30a2\u30a6\u30c8\uff09\n std::mdspan mat{arr, std::extents<size_t, 3, 2>{}};\n static_assert(std::same_as<decltype(mat)::layout_type, std::layout_right>);\n // 1 2\n // 3 4\n // 5 6\n\n // \u884c\u512a\u5148\u30ec\u30a4\u30a2\u30a6\u30c8 std::layout_right \u3092\u7dad\u6301\n auto row0 = std::submdspan(mat, 0, std::full_extent);\n // 1 2\n auto row12 = std::submdspan(mat, std::pair{1,3}, std::full_extent);\n // 3 4\n // 5 6\n static_assert(std::same_as<decltype(row0)::layout_type, std::layout_right>);\n static_assert(std::same_as<decltype(row12)::layout_type, std::layout_right>);\n\n // \u6c4e\u7528\u30b9\u30c8\u30e9\u30a4\u30c9\u6307\u5b9a\u30ec\u30a4\u30a2\u30a6\u30c8 std::layout_stride \u306b\u5909\u63db\n auto col1 = std::submdspan(mat, std::full_extent, 1);\n // 2 4 6\n auto row02 = std::submdspan(mat,\n std::strided_slice{.offset=0, .extent=3, .stride=2},\n std::full_extent);\n // 1 2\n // 5 6\n static_assert(std::same_as<decltype(col1)::layout_type, std::layout_stride>);\n static_assert(std::same_as<decltype(row02)::layout_type, std::layout_stride>);\n}\n"}], "page_id": ["reference", "mdspan", "submdspan"]}">
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2026年08月12日 17時16分46秒 (JST)
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<div class="identifier-type">function template</div><div class="header"><mdspan></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">submdspan</span><span class="cpp cpp26" title="C++26で追加">(C++26)</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="o"><</span>
<span class="w"> </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="k">class</span><span class="w"> </span><span class="nc"><a href="extents.html">Extents</a></span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc"><a href="LayoutMappingPolicy.html">LayoutPolicy</a></span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc"><a href="AccessorPolicy.html">AccessorPolicy</a></span><span class="p">,</span>
<span class="w"> </span><span class="k">class</span><span class="p">...</span><span class="w"> </span><span class="n">SliceSpecifiers</span><span class="o">></span>
<span class="w"> </span><span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">submdspan</span><span class="p">(</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="mdspan.html">mdspan</a></span><span class="o"><</span><span class="n">ElementType</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="extents.html">Extents</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="LayoutMappingPolicy.html">LayoutPolicy</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="AccessorPolicy.html">AccessorPolicy</a></span><span class="o">>&</span><span class="w"> </span><span class="n">src</span><span class="p">,</span>
<span class="w"> </span><span class="n">SliceSpecifiers</span><span class="p">...</span><span class="w"> </span><span class="n">slices</span><span class="p">)</span><span class="w"> </span><span class="o">-></span><span class="w"> </span><span class="n"><i>see below</i></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p>多次元配列ビュー<code><a href="mdspan.html">mdspan</a></code>と各次元からの要素取り出し（スライス）方式を指定して、メモリブロックに対する新しい多次元配列ビュー<code><a href="mdspan.html">mdspan</a></code>を取得する。</p>
<h3>スライス指定</h3>
<p>各次元からの要素取り出し方式は、下記の4種類をサポートする。
スライス指定子リスト<code>slices...</code>にインデクス値指定が含まれる場合、<a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a>の次元数(rank)は元の多次元配列ビューに対してインデクス値指定した次元数だけ削減される。</p>
<ul>
<li>インデクス値指定 : 整数値。指定次元に対する多次元インデクス値を固定する。</li>
<li>インデクス範囲指定 : <a href="index-pair-like.html">インデクス・ペア互換型</a>の値。開始位置(begin)と終了位置(end)で表現される半開区間から要素群を取り出す。</li>
<li>ストライド・スライス指定 : <code><a href="strided_slice.html">std::strided_slice</a></code>の値。オフセット(offset)と要素数(extent)とストライド幅(stride)で指定される要素群を取り出す。</li>
<li>全要素指定 : <code><a href="full_extent_t.html">std::full_extent</a></code>。指定次元の全要素を取り出す。</li>
</ul>
<h3>カスタマイゼーションポイント</h3>
<p><code>submdspan</code>関数により<code><a href="mdspan.html">mdspan</a></code>から部分ビューを取り出すには、変換元の<a href="LayoutMapping.html">レイアウトマッピング型</a>がカスタマイゼーションポイント<code>submdspan_mapping</code>を実装している必要がある。</p>
<h2><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></h2>
<ul>
<li><code>sizeof...(slices)</code>が<code><a href="extents/rank.html">Extents::rank()</a></code>と等しい</li>
<li><code>LayoutPolicy::mapping<Extents></code>が<code><a href="sliceable-mapping.html">sliceable-mapping</a></code>のモデルである。</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Mandates。満たさなければプログラムが不適格となる要件。この要件は、オーバーロード解決によって選択された関数内での`static_assert`の定数条件式や、関数に対するdelete宣言などで表現できる">適格要件</a></h2>
<p><code>src</code>の各次元インデクス<code>k</code>に対して、</p>
<ul>
<li><code>SliceSpecifiers...[k]</code>が<code>index_type</code>の<code>submdspan</code>スライス型であり、かつ</li>
<li><code>decltype(slices...[k])</code>が<code>Extents</code>のk番目の次元に対する有効な<code>submdspan</code>スライス型であること。</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Preconditions。関数呼び出し時に満たされていると関数が想定する条件。満たさなければ未定義の動作。契約属性の`[[expects]]`に相当">事前条件</a></h2>
<p><code><a href="mdspan/extents.html">src.extents()</a></code>の各次元インデクス<code>k</code>に対して、<code>slices...[k]</code>が<code>src.extents()</code>のk番目の要素に対する有効な<code>submdspan</code>スライスであること。</p>
<h2>効果</h2>
<p>以下と等価</p>
<p><div class="codehilite"><pre><span></span><code><span class="k">auto</span><span class="w"> </span><span class="p">[...</span><span class="n">slices</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="canonical_slices.html">canonical_slices</a></span><span class="p">(</span><span class="n">src</span><span class="p">,</span><span class="w"> </span><span class="n">raw_slices</span><span class="p">...);</span>
<span class="k">auto</span><span class="w"> </span><span class="n"><a href="submdspan_mapping_result.html">sub_map_offset</a></span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">submdspan_mapping</span><span class="p">(</span><span class="n"><a href="mdspan/mapping.html">src.mapping()</a></span><span class="p">,</span><span class="w"> </span><span class="n">slices</span><span class="p">...);</span>
<span class="k">return</span><span class="w"> </span><span class="n"><a href="mdspan.html">mdspan</a></span><span class="p">(</span><span class="n"><a href="mdspan/accessor.html">src.accessor()</a></span><span class="p">.</span><span class="n">offset</span><span class="p">(</span><span class="n"><a href="mdspan/data_handle.html">src.data_handle()</a></span><span class="p">,</span><span class="w"> </span><span class="n"><a href="submdspan_mapping_result.html">sub_map_offset</a></span><span class="p">.</span><span class="n">offset</span><span class="p">),</span>
<span class="w"> </span><span class="n"><a href="submdspan_mapping_result.html">sub_map_offset</a></span><span class="p">.</span><span class="n">mapping</span><span class="p">,</span>
<span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc"><a href="AccessorPolicy.html">AccessorPolicy::offset_policy</a></span><span class="p">(</span><span class="n"><a href="mdspan/accessor.html">src.accessor()</a></span><span class="p">));</span>
</code></pre></div>
</p>
<h2>例</h2>
<h3>基本的な使い方</h3>
<p><div class="yata" id="e0290321d286586529963e74c83e922689ccd679"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../mdspan.html"><mdspan></a></span>
<span class="cp">#include <a href="../numeric.html"><numeric></a></span>
<span class="cp">#include <a href="../print.html"><print></a></span>
<span class="cp">#include <a href="../string_view.html"><string_view></a></span>
<span class="cp">#include <a href="../utility.html"><utility></a></span>
<span class="c1">// 2次元配列ビュー(Matrix)の要素表示</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</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">E</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">L</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">A</span><span class="o">></span>
<span class="kt">void</span><span class="w"> </span><span class="n">print_mat</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">name</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="mdspan.html">std::mdspan</a></span><span class="o"><</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">L</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">mat</span><span class="p">)</span>
<span class="p">{</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">mat</span><span class="p">.</span><span class="n">rank</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"{}:"</span><span class="p">,</span><span class="w"> </span><span class="n">name</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">size_t</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">mat</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">0</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="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">size_t</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">j</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">mat</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span><span class="w"> </span><span class="o">++</span><span class="n">j</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="../print/print.html">std::print</a></span><span class="p">(</span><span class="s">" {:2}"</span><span class="p">,</span><span class="w"> </span><span class="n">mat</span><span class="p">[</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">]);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">""</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
<span class="c1">// 1次元配列ビュー(Vector)の要素表示</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</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">E</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">L</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">A</span><span class="o">></span>
<span class="kt">void</span><span class="w"> </span><span class="n">print_vec</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">name</span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="mdspan.html">std::mdspan</a></span><span class="o"><</span><span class="n">T</span><span class="p">,</span><span class="w"> </span><span class="n">E</span><span class="p">,</span><span class="w"> </span><span class="n">L</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">mat</span><span class="p">)</span>
<span class="p">{</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">mat</span><span class="p">.</span><span class="n">rank</span><span class="p">()</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="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"{}:"</span><span class="p">,</span><span class="w"> </span><span class="n">name</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">size_t</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">mat</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">0</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="../print/print.html">std::print</a></span><span class="p">(</span><span class="s">" {:2}"</span><span class="p">,</span><span class="w"> </span><span class="n">mat</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"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">""</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="kt">int</span><span class="w"> </span><span class="n">arr</span><span class="p">[</span><span class="mi">20</span><span class="p">];</span>
<span class="w"> </span><span class="n"><a href="../numeric/ranges_iota.html">std::ranges::iota</a></span><span class="p">(</span><span class="n">arr</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">// 4x5要素の2次元配列ビュー</span>
<span class="w"> </span><span class="k">using</span><span class="w"> </span><span class="n">Ext2D</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="extents.html">std::dextents</a></span><span class="o"><</span><span class="kt">size_t</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="o">></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="mdspan.html">std::mdspan</a></span><span class="w"> </span><span class="n">mat</span><span class="p">{</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n">Ext2D</span><span class="p">{</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="n">print_mat</span><span class="p">(</span><span class="s">"mat"</span><span class="p">,</span><span class="w"> </span><span class="n">mat</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// インデクス値指定＋全要素指定（2次元→1次元）</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">row1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="full_extent_t.html">std::full_extent</a></span><span class="p">);</span>
<span class="w"> </span><span class="n">print_vec</span><span class="p">(</span><span class="s">"mat[1,M]"</span><span class="p">,</span><span class="w"> </span><span class="n">row1</span><span class="p">);</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">col2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="full_extent_t.html">std::full_extent</a></span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span>
<span class="w"> </span><span class="n">print_vec</span><span class="p">(</span><span class="s">"mat[N,2]"</span><span class="p">,</span><span class="w"> </span><span class="n">col2</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 単一要素の取り出し（2次元→0次元）</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">elem</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"mat[1,2]:</span><span class="se">\n</span><span class="s"> {:2}"</span><span class="p">,</span><span class="w"> </span><span class="n">elem</span><span class="p">[]);</span>
<span class="w"> </span><span class="c1">// インデクス範囲指定</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">submat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../utility/pair.html">std::pair</a></span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="n"><a href="../utility/pair.html">std::pair</a></span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">4</span><span class="p">});</span>
<span class="w"> </span><span class="n">print_mat</span><span class="p">(</span><span class="s">"submat"</span><span class="p">,</span><span class="w"> </span><span class="n">submat</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// ストライド・スライス指定</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">strided</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span>
<span class="w"> </span><span class="n"><a href="strided_slice.html">std::strided_slice</a></span><span class="p">{.</span><span class="n">offset</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">extent</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">stride</span><span class="o">=</span><span class="mi">2</span><span class="p">},</span><span class="w"> </span>
<span class="w"> </span><span class="n"><a href="strided_slice.html">std::strided_slice</a></span><span class="p">{.</span><span class="n">offset</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">extent</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">stride</span><span class="o">=</span><span class="mi">2</span><span class="p">});</span>
<span class="w"> </span><span class="n">print_mat</span><span class="p">(</span><span class="s">"strided"</span><span class="p">,</span><span class="w"> </span><span class="n">strided</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code>mat:
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
mat[1,M]:
6 7 8 9 10
mat[N,2]:
3 8 13 18
mat[1,2]:
8
submat:
7 8 9
12 13 14
strided:
6 8 10
16 18 20
</code></pre></p>
<h3>静的要素数mdspanの生成</h3>
<p><div class="yata" id="154d20bbd1a205c8572508587ad781937b65c78d"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../concepts.html"><concepts></a></span>
<span class="cp">#include <a href="../mdspan.html"><mdspan></a></span>
<span class="cp">#include <a href="../numeric.html"><numeric></a></span>
<span class="cp">#include <a href="../print.html"><print></a></span>
<span class="cp">#include <a href="../utility.html"><utility></a></span>
<span class="c1">// 整数定数型</span>
<span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="kt">int</span><span class="w"> </span><span class="n">N</span><span class="o">></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">Int</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../type_traits/integral_constant.html">std::integral_constant</a></span><span class="o"><</span><span class="kt">int</span><span class="p">,</span><span class="w"> </span><span class="n">N</span><span class="o">></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="kt">int</span><span class="w"> </span><span class="n">arr</span><span class="p">[</span><span class="mi">20</span><span class="p">];</span>
<span class="w"> </span><span class="n"><a href="../numeric/ranges_iota.html">std::ranges::iota</a></span><span class="p">(</span><span class="n">arr</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">// 静的要素数 4x5 の2次元配列ビュー</span>
<span class="w"> </span><span class="n"><a href="mdspan.html">std::mdspan</a></span><span class="w"> </span><span class="n">mat</span><span class="p">{</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="extents.html">std::extents</a></span><span class="o"><</span><span class="kt">size_t</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="o">></span><span class="p">{}};</span>
<span class="w"> </span><span class="c1">// 動的要素数 2x3 の2次元配列部分ビューを取り出し</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">submat_dyn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span>
<span class="w"> </span><span class="n"><a href="../utility/pair.html">std::pair</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="n"><a href="strided_slice.html">std::strided_slice</a></span><span class="p">{.</span><span class="n">offset</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">extent</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">stride</span><span class="o">=</span><span class="mi">2</span><span class="p">});</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">submat_dyn</span><span class="p">)</span><span class="o">::</span><span class="n">extents_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="extents.html">std::dextents</a></span><span class="o"><</span><span class="kt">size_t</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="o">>></span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"submat_dyn {}x{}"</span><span class="p">,</span><span class="w"> </span><span class="n">submat_dyn</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">0</span><span class="p">),</span><span class="w"> </span><span class="n">submat_dyn</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">1</span><span class="p">));</span>
<span class="w"> </span><span class="c1">// 静的要素数 2x3 の2次元配列部分ビューを取り出し</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">submat_2x3</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span>
<span class="w"> </span><span class="n"><a href="../utility/pair.html">std::pair</a></span><span class="p">{</span><span class="n">Int</span><span class="o"><</span><span class="mi">1</span><span class="o">></span><span class="p">,</span><span class="w"> </span><span class="n">Int</span><span class="o"><</span><span class="mi">3</span><span class="o">></span><span class="p">},</span>
<span class="w"> </span><span class="n"><a href="strided_slice.html">std::strided_slice</a></span><span class="p">{.</span><span class="n">offset</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">extent</span><span class="o">=</span><span class="n">Int</span><span class="o"><</span><span class="mi">5</span><span class="o">></span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">stride</span><span class="o">=</span><span class="n">Int</span><span class="o"><</span><span class="mi">2</span><span class="o">></span><span class="p">});</span>
<span class="w"> </span><span class="c1">// (strided_slice::offset は戻り値型に影響を与えない)</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">submat_2x3</span><span class="p">)</span><span class="o">::</span><span class="n">extents_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="extents.html">std::extents</a></span><span class="o"><</span><span class="kt">size_t</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="o">>></span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"submat_2x3 {}x{}"</span><span class="p">,</span><span class="w"> </span><span class="n">submat_2x3</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">0</span><span class="p">),</span><span class="w"> </span><span class="n">submat_2x3</span><span class="p">.</span><span class="n">extent</span><span class="p">(</span><span class="mi">1</span><span class="p">));</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code>submat_dyn 2x3
submat_2x3 2x3
</code></pre></p>
<h3>レイアウトマッピング互換性</h3>
<p><div class="yata" id="4a6f4af3a755612953df799a2870a4ab692364db"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../mdspan.html"><mdspan></a></span>
<span class="cp">#include <a href="../utility.html"><utility></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="kt">int</span><span class="w"> </span><span class="n">arr</span><span class="p">[</span><span class="mi">6</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="mi">6</span><span class="p">};</span>
<span class="w"> </span><span class="c1">// 3x2要素の2次元配列ビュー（行優先レイアウト）</span>
<span class="w"> </span><span class="n"><a href="mdspan.html">std::mdspan</a></span><span class="w"> </span><span class="n">mat</span><span class="p">{</span><span class="n">arr</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="extents.html">std::extents</a></span><span class="o"><</span><span class="kt">size_t</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">2</span><span class="o">></span><span class="p">{}};</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">mat</span><span class="p">)</span><span class="o">::</span><span class="n">layout_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="layout_right.html">std::layout_right</a></span><span class="o">></span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 1 2</span>
<span class="w"> </span><span class="c1">// 3 4</span>
<span class="w"> </span><span class="c1">// 5 6</span>
<span class="w"> </span><span class="c1">// 行優先レイアウト <a href="layout_right.html">std::layout_right</a> を維持</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">row0</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="full_extent_t.html">std::full_extent</a></span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 1 2</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">row12</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../utility/pair.html">std::pair</a></span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">},</span><span class="w"> </span><span class="n"><a href="full_extent_t.html">std::full_extent</a></span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 3 4</span>
<span class="w"> </span><span class="c1">// 5 6</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">row0</span><span class="p">)</span><span class="o">::</span><span class="n">layout_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="layout_right.html">std::layout_right</a></span><span class="o">></span><span class="p">);</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">row12</span><span class="p">)</span><span class="o">::</span><span class="n">layout_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="layout_right.html">std::layout_right</a></span><span class="o">></span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 汎用ストライド指定レイアウト <a href="layout_stride.html">std::layout_stride</a> に変換</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">col1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="full_extent_t.html">std::full_extent</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">// 2 4 6</span>
<span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">row02</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::submdspan</span></span><span class="p">(</span><span class="n">mat</span><span class="p">,</span>
<span class="w"> </span><span class="n"><a href="strided_slice.html">std::strided_slice</a></span><span class="p">{.</span><span class="n">offset</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">extent</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="p">.</span><span class="n">stride</span><span class="o">=</span><span class="mi">2</span><span class="p">},</span>
<span class="w"> </span><span class="n"><a href="full_extent_t.html">std::full_extent</a></span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 1 2</span>
<span class="w"> </span><span class="c1">// 5 6</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">col1</span><span class="p">)</span><span class="o">::</span><span class="n">layout_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="layout_stride.html">std::layout_stride</a></span><span class="o">></span><span class="p">);</span>
<span class="w"> </span><span class="k">static_assert</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n"><a href="../concepts/same_as.html">same_as</a></span><span class="o"><</span><span class="k">decltype</span><span class="p">(</span><span class="n">row02</span><span class="p">)</span><span class="o">::</span><span class="n">layout_type</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="layout_stride.html">std::layout_stride</a></span><span class="o">></span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code></code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++26</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: ??</li>
<li><a href="../../implementation.html#gcc">GCC</a>: ??</li>
<li><a href="../../implementation.html#icc">ICC</a>: ??</li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: ??</li>
</ul>
<h2>関連項目</h2>
<ul>
<li><code><a href="mdspan.html">mdspan</a></code></li>
<li><code><a href="full_extent_t.html">full_extent</a></code></li>
<li><code><a href="strided_slice.html">strided_slice</a></code></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2630r4.html" target="_blank">P2630R4 Submdspan</a></li>
<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2025/p3663r3.html" target="_blank">P3663R3 Future-proof <code>submdspan_mapping</code></a></li>
</ul></div>
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