117 lines
10 KiB
HTML
117 lines
10 KiB
HTML
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<title>std::rotr</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_rotr skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>rotr</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-numeric.html">numeric</a></span></div>
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<td>
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<div>定义于头文件 <code><a href="cpp-header-bit.html"><bit></a></code></div>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> T<span class="sy1">></span><br />
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<span class="br0">[</span><span class="br0">[</span>nodiscard<span class="br0">]</span><span class="br0">]</span> <span class="kw4">constexpr</span> T rotr<span class="br0">(</span>T x, <span class="kw4">int</span> s<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<td></td>
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<p>计算将 <code>x</code> 右旋转 <code>s</code> 位的结果。此运算被称为<a rel="nofollow" class="external text" href="https://en.wikipedia.org/wiki/Circular_shift">循环移位</a>。</p>
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<p>正式而言，令 <code>N</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-numeric_limits.html"><span class="kw344">std::<span class="me2">numeric_limits</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="sy4">::</span><span class="me2">digits</span></span></span> ， <code>r</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp">s <span class="sy2">%</span> N</span></span> 。</p>
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<ul>
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<li>若 <code>r</code> 为 0 ，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">x</span></span> ；</li>
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<li>若 <code>r</code> 为正，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span>x <span class="sy1">>></span> r<span class="br0">)</span> <span class="sy3">|</span> <span class="br0">(</span>x <span class="sy1"><<</span> <span class="br0">(</span>N <span class="sy2">-</span> r<span class="br0">)</span><span class="br0">)</span></span></span> ；</li>
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<li>若 <code>r</code> 为负，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">rotl</span><span class="br0">(</span>x, <span class="sy2">-</span>r<span class="br0">)</span></span></span> 。</li>
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</ul>
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<p>此重载仅若 <code>T</code> 为无符号整数类型（即 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">char</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">short</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">int</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span></span></span> 、 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">long</span> <span class="kw4">long</span></span></span> 或扩展无符号整数类型）才参与重载决议。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>x</td>
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<td>-</td>
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<td>无符号整数类型的值</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>将 <code>x</code> 右旋转 <code>s</code> 位的结果。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <bit></span>
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<span class="co2">#include <bitset></span>
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<span class="co2">#include <cstdint></span>
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<span class="co2">#include <iostream></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-types-integer.html"><span class="kw120">std::<span class="me2">uint8_t</span></span></a> i <span class="sy1">=</span> <span class="nu6">0b00011101</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"i = "</span> <span class="sy1"><<</span> <a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1"><</span><span class="nu0">8</span><span class="sy1">></span><span class="br0">(</span>i<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"rotr(i,0) = "</span> <span class="sy1"><<</span> <a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1"><</span><span class="nu0">8</span><span class="sy1">></span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">rotr</span><span class="br0">(</span>i,<span class="nu0">0</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"rotr(i,1) = "</span> <span class="sy1"><<</span> <a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1"><</span><span class="nu0">8</span><span class="sy1">></span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">rotr</span><span class="br0">(</span>i,<span class="nu0">1</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"rotr(i,9) = "</span> <span class="sy1"><<</span> <a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1"><</span><span class="nu0">8</span><span class="sy1">></span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">rotr</span><span class="br0">(</span>i,<span class="nu0">9</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"rotr(i,-1) = "</span> <span class="sy1"><<</span> <a href="cpp-utility-bitset.html"><span class="kw1027">std::<span class="me2">bitset</span></span></a><span class="sy1"><</span><span class="nu0">8</span><span class="sy1">></span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">rotr</span><span class="br0">(</span>i,<span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">i = 00011101
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rotr(i,0) = 00011101
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rotr(i,1) = 10001110
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rotr(i,9) = 10001110
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rotr(i,-1) = 00111010</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-rotl.html"><span class="t-lines"><span>rotl</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>计算逐位左旋转的结果<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-bitset-operator_ltltgtgt.html"><span class="t-lines"><span>operator<<=</span><span>operator>>=</span><span>operator<<</span><span>operator>></span></span></a></div>
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</div>
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</td>
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<td>进行二进制左移和右移<br />
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<span class="t-mark">(<code>std::bitset<N></code> 的公开成员函数)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</body>
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