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<div class="identifier-type">class template</div><div class="header"><random></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">uniform_int_distribution</span><span class="cpp cpp11" title="C++11で追加">(C++11)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">IntType</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kt">int</span><span class="o">></span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">uniform_int_distribution</span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code>uniform_int_distribution</code>は、指定された範囲の値が等確率で発生するよう離散分布するクラスである。
このクラスは、離散一様分布(Discrete Uniform Distribution)の整数に特化したバージョンである。実数が必要な場合は、<code><a href="uniform_real_distribution.html">uniform_real_distribution</a></code>クラスを使用する。</p>
<p>一様分布の整数は、以下のような用途で使用できる：</p>
<ul>
<li>サイコロを振る</li>
<li>カードデッキから1枚を選ぶ</li>
</ul>
<p>テンプレートパラメータは、以下を意味する：</p>
<ul>
<li><code>IntType</code> : 生成する整数の型。標準の符号付き／符号なし整数型 (<code>signed char</code>、<code>unsigned char</code>を含む) 、拡張整数型 (ビット幅が<code>char</code>以上<code>long long</code>以下) 、または<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">処理系定義</a>のサブセットの整数型でなければならない。</li>
</ul>
<h2>メンバ関数</h2>
<h3>構築・リセット</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="uniform_int_distribution/op_constructor.html">(constructor)</a></code></td>
<td>コンストラクタ</td>
<td>C++11</td>
</tr>
<tr>
<td><code>~uniform_int_distribution() = default;</code></td>
<td>デストラクタ</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/reset.html">reset</a></code></td>
<td>状態をリセットする</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h3>生成</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="uniform_int_distribution/op_call.html">operator()</a></code></td>
<td>乱数を生成する</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h3>プロパティ</h3>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="uniform_int_distribution/a.html">a</a></code></td>
<td>生成し得る値の下限を取得する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/b.html">b</a></code></td>
<td>生成し得る値の上限を取得する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/param.html">param</a></code></td>
<td>分布のパラメータを取得／設定する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/min.html">min</a></code></td>
<td>生成し得る値の下限を取得する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/max.html">max</a></code></td>
<td>生成し得る値の上限を取得する</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>メンバ型</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>型</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>result_type</code></td>
<td>乱数生成結果の整数型 <code>IntType</code>。符号なし整数型でもよい。</td>
<td>C++11</td>
</tr>
<tr>
<td><code>param_type</code></td>
<td>分布パラメータの型。<a class="cpprefjp-defined-word" data-desc="未規定の動作。事前の断りなく処理系によって異なる動作をする" href="../../implementation-compliance.html#dfn-unspecified-behavior">未規定</a>。</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>非メンバ関数</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="uniform_int_distribution/op_equal.html">operator==</a></code></td>
<td>等値比較</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/op_not_equal.html">operator!=</a></code></td>
<td>非等値比較</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/op_ostream.html">operator<<</a></code></td>
<td>ストリームへの出力</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="uniform_int_distribution/op_istream.html">operator>></a></code></td>
<td>ストリームからの入力</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>例</h2>
<p><div class="yata" id="3a92bace3f98043df4b0b23c0ee020884b973582"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../random.html"><random></a></span>
<span class="cp">#include <a href="../fstream.html"><fstream></a></span>
<span class="cp">#include <a href="../cstdint.html"><cstdint></a></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"><a href="random_device.html">std::random_device</a></span><span class="w"> </span><span class="n">seed_gen</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../cstdint/uint32_t.html">std::uint32_t</a></span><span class="w"> </span><span class="n">seed</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">seed_gen</span><span class="p">();</span>
<span class="w"> </span><span class="n"><a href="default_random_engine.html">std::default_random_engine</a></span><span class="w"> </span><span class="n">engine</span><span class="p">(</span><span class="n">seed</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 0以上9以下の値を等確率で発生させる</span>
<span class="w"> </span><span class="n"><span style="color:#ff0000">std::uniform_int_distribution</span></span><span class="o"><></span><span class="w"> </span><span class="n">dist</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../fstream/basic_ofstream.html">std::ofstream</a></span><span class="w"> </span><span class="n">result_file</span><span class="p">(</span><span class="s">"uniform_int_distribution.tsv"</span><span class="p">);</span>
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n"><a href="../cstddef/size_t.html">std::size_t</a></span><span class="w"> </span><span class="n">n</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">n</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">1000</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// 一様整数分布で乱数を生成する</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="uniform_int_distribution/op_call.html">dist(engine)</a></span><span class="p">;</span>
<span class="w"> </span><span class="n">result_file</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"</span><span class="se">\t\n</span><span class="s">"</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code></code></pre></p>
<p>このプログラムによってある時に得られた結果（<a href="https://github.com/cpprefjp/image/blob/master/reference/random/uniform_int_distribution/uniform_int_distribution.tsv" target="_blank">uniform_int_distribution.tsv</a>）を図示する。</p>
<p><img alt="" src="../../static/image/reference/random/uniform_int_distribution/uniform_int_distribution.png" /></p>
<p>1,000個程度のデータのため、ある程度は偏りがあるが、誤差の範囲でほぼ等確率で0から9までの値が生成されていることがわかる。</p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++11</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: ??</li>
<li><a href="../../implementation.html#gcc">GCC</a>: 4.7.2 <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>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://lemire.me/blog/2019/09/28/doubling-the-speed-of-stduniform_int_distribution-in-the-gnu-c-library/" target="_blank">Doubling the speed of <code>std::uniform_int_distribution</code> in the GNU C++ library - Daniel Lemire's blog</a></li>
<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2026/p4037r1.html" target="_blank">P4037R1 Supporting <code>signed char</code> and <code>unsigned char</code> in random number generation</a><ul>
<li><code>IntType</code>テンプレートパラメータに<code>signed char</code>／<code>unsigned char</code>を指定できるようになった。この仕様はC++26から導入されたが、仕様の欠陥を修正したものであるためコンパイラは早期に対応している場合がある</li>
</ul>
</li>
</ul></div>
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