182 lines
15 KiB
HTML
182 lines
15 KiB
HTML
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<title>std::cos(std::valarray)</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_numeric_valarray_cos 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>cos<span style="font-size:0.7em; line-height:130%">(std::valarray)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-numeric.html">numeric</a>‎ | <a href="cpp-numeric-valarray.html">valarray</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-valarray.html"><valarray></a></code></div>
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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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valarray<span class="sy1"><</span>T<span class="sy1">></span> cos<span class="br0">(</span> <span class="kw4">const</span> valarray<span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span> va <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>对 <code>va</code> 中每个元素计算元素值的余弦。</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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<td>va</td>
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<td>-</td>
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<td>要应用操作到的值数组</td>
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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>含有 <code>va</code> 中值的余弦的值数组。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>用无限定函数 (<span class="t-c"><span class="mw-geshi cpp source-cpp">cos</span></span>) 进行计算。若该函数不可用，则因参数依赖查找使用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-numeric-math-cos.html"><span class="kw1334">std::<span class="me2">cos</span></span></a></span></span> 。</p>
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<p>函数能实现为拥有不同于 <span class="t-lc"><a href="cpp-numeric-valarray.html">std::valarray</a></span> 的返回类型。此情况下，替换类型拥有下列属性：</p>
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<li>提供 <span class="t-lc"><a href="cpp-numeric-valarray.html">std::valarray</a></span> 的所有 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span></span></span> 成员函数。</li>
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<li>能从替换类型构造 <span class="t-lc"><a href="cpp-numeric-valarray.html">std::valarray</a></span> 、 <span class="t-lc"><a href="cpp-numeric-valarray-slice_array.html">std::slice_array</a></span> 、 <span class="t-lc"><a href="cpp-numeric-valarray-gslice_array.html">std::gslice_array</a></span> 、 <span class="t-lc"><a href="cpp-numeric-valarray-mask_array.html">std::mask_array</a></span> 和 <span class="t-lc"><a href="cpp-numeric-valarray-indirect_array.html">std::indirect_array</a></span> 。</li>
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<li>所有接受一个 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy3">&</span></span></span> 类型参数的函数<span class="t-rev-inl t-since-cxx11"><span>，除了 <a href="cpp-numeric-valarray-begin2.html"><tt>begin()</tt></a> 和 <a href="cpp-numeric-valarray-end2.html"><tt>end()</tt></a></span> <span><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></span></span>也应该接受替换类型。</li>
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<li>所有接受二个 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy3">&</span></span></span> 类型参数的函数都应该接受 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy3">&</span></span></span> 和替换类型的每种组合。</li>
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<li>返回类型添加不多于二层嵌套在最深层嵌套的参数类型上的模板。</li>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> T<span class="sy1">></span>
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valarray<span class="sy1"><</span>T<span class="sy1">></span> cos<span class="br0">(</span><span class="kw4">const</span> valarray<span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span> va<span class="br0">)</span>
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<span class="br0">{</span>
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valarray<span class="sy1"><</span>T<span class="sy1">></span> other <span class="sy1">=</span> va<span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span>T <span class="sy3">&</span>i <span class="sy4">:</span> other<span class="br0">)</span> <span class="br0">{</span>
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i <span class="sy1">=</span> cos<span class="br0">(</span>i<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">return</span> other<span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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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 <cmath></span>
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<span class="co2">#include <iomanip></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <valarray></span>
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<span class="kw4">void</span> show<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> title, <span class="kw4">const</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span><span class="sy3">&</span> data<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">const</span> <span class="kw4">int</span> w <span class="br0">{</span> <span class="nu0">9</span> <span class="br0">}</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> <a href="cpp-io-manip-setw.html"><span class="kw1797">std::<span class="me2">setw</span></span></a><span class="br0">(</span>w<span class="br0">)</span> <span class="sy1"><<</span> title <span class="sy1"><<</span> <span class="st0">" | "</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">float</span> x <span class="sy4">:</span> data<span class="br0">)</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> <a href="cpp-io-manip-setw.html"><span class="kw1797">std::<span class="me2">setw</span></span></a><span class="br0">(</span>w<span class="br0">)</span> <span class="sy1"><<</span> x <span class="sy1"><<</span> <span class="st0">" | "</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">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</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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<span class="kw4">const</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span><span class="kw4">float</span><span class="sy1">></span> x <span class="br0">{</span> <span class="nu18">.1</span>, <span class="nu18">.2</span>, <span class="nu18">.3</span>, <span class="nu18">.4</span> <span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> sin <span class="sy1">=</span> <a href="cpp-numeric-math-sin.html"><span class="kw1333">std::<span class="me2">sin</span></span></a><span class="br0">(</span>x<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> cos <span class="sy1">=</span> <a href="cpp-numeric-math-cos.html"><span class="kw1334">std::<span class="me2">cos</span></span></a><span class="br0">(</span>x<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> z <span class="sy1">=</span> <span class="br0">(</span>sin <span class="sy2">*</span> sin<span class="br0">)</span> <span class="sy2">+</span> <span class="br0">(</span>cos <span class="sy2">*</span> cos<span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"x"</span> , x <span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"sin(x)"</span>, sin<span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"cos(x)"</span>, cos<span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"z"</span> , z <span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</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">
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x | 0.1 | 0.2 | 0.3 | 0.4 |
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sin(x) | 0.0998334 | 0.198669 | 0.29552 | 0.389418 |
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cos(x) | 0.995004 | 0.980067 | 0.955337 | 0.921061 |
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z | 1 | 1 | 1 | 1 |</pre></div>
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</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-valarray-sin.html"><span class="t-lines"><span>sin<span class="t-dsc-small">(std::valarray)</span></span></span></a></div>
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</div>
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</td>
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<td>对 valarray 的每个元素应用<span class="t-lc"><a href="cpp-numeric-math-sin.html">std::sin</a></span>函数<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-valarray-tan.html"><span class="t-lines"><span>tan<span class="t-dsc-small">(std::valarray)</span></span></span></a></div>
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</div>
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</td>
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<td>应用函数 <span class="t-lc"><a href="cpp-numeric-math-tan.html">std::tan</a></span> 到 valarray 的每个元素<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-valarray-acos.html"><span class="t-lines"><span>acos<span class="t-dsc-small">(std::valarray)</span></span></span></a></div>
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</div>
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</td>
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<td>应用函数 <span class="t-lc"><a href="cpp-numeric-math-acos.html">std::acos</a></span> 到 valarray 的每个元素<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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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-math-cos.html"><span class="t-lines"><span>cos</span><span>cosf</span><span>cosl</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>计算余弦（ <span class="mjax" style="display:none">\({\small\cos{x} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">cos(x)</span> ）<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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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-numeric-complex-cos.html"><span class="t-lines"><span>cos<span class="t-dsc-small">(std::complex)</span></span></span></a></div>
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</div>
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</td>
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<td>计算复数的余弦（ <span class="mjax" style="display:none">\({\small\cos{z} }\)</span><span class="mjax-fallback texhtml" style="white-space: nowrap;">cos(z)</span> ）<br />
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<span class="t-mark">(函数模板)</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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