209 lines
21 KiB
HTML
209 lines
21 KiB
HTML
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<title>std::atan2(std::valarray)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>atan2<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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<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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<a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span>T<span class="sy1">></span> atan2<span class="br0">(</span> <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>T<span class="sy1">></span><span class="sy3">&</span> y, <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>T<span class="sy1">></span><span class="sy3">&</span> x <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</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 /></span>
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<p><a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span>T<span class="sy1">></span> atan2<span class="br0">(</span> <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>T<span class="sy1">></span><span class="sy3">&</span> y,<br /></p>
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<span class="kw4">const</span> <span class="kw1">typename</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="sy4">::</span><span class="me2">value_type</span><span class="sy3">&</span> vx <span class="br0">)</span><span class="sy4">;</span></div>
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<td>(2)</td>
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<td class="t-dcl-nopad"></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 /></span>
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<p><a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span>T<span class="sy1">></span> atan2<span class="br0">(</span> <span class="kw4">const</span> <span class="kw1">typename</span> <a href="cpp-numeric-valarray.html"><span class="kw1473">std::<span class="me2">valarray</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="sy4">::</span><span class="me2">value_type</span><span class="sy3">&</span> vy,<br /></p>
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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>T<span class="sy1">></span><span class="sy3">&</span> x <span class="br0">)</span><span class="sy4">;</span></div>
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<td>(3)</td>
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<td class="t-dcl-nopad"></td>
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<td></td>
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<td></td>
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<p>计算 <code>y/x</code> 的反正切，用参数符号正确地确定象限。</p>
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<div class="t-li1"><span class="t-li">1)</span> 计算每对来自 <code>y</code> 与 <code>x</code> 的对应值的反正切。</div>
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<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">x.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> y.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span></span></span> 则行为未定义。</p>
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<div class="t-li1"><span class="t-li">2)</span> 计算 <code>vx</code> 与数值数组 <code>y</code> 中每个值的反正切。</div>
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<div class="t-li1"><span class="t-li">3)</span> 计算 <code>vy</code> 与数值数组 <code>x</code> 中每个值的反正切。</div>
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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, y</td>
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<td>-</td>
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<td>要计算反正切的数值数组</td>
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</tr>
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<tr class="t-par">
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<td>vy, vx</td>
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<td>-</td>
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<td>要计算反正切的值</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>含反正切计算结果的数值数组。</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">atan2</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-atan2.html"><span class="kw1339">std::<span class="me2">atan2</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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<dl>
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<dd>
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<ul>
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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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</ul>
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</dd>
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</dl>
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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 dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <algorithm></span>
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<span class="co2">#include <cmath></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <iomanip></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">char</span> <span class="kw4">const</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">double</span><span class="sy1">></span><span class="sy3">&</span> va<span class="br0">)</span> <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> title <span class="sy1"><<</span> <span class="st0">" "</span><span class="sy4">;</span>
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<a href="cpp-algorithm-for_each.html"><span class="kw1568">std::<span class="me2">for_each</span></span></a><span class="br0">(</span><a href="cpp-iterator-begin.html"><span class="kw676">std::<span class="me2">begin</span></span></a><span class="br0">(</span>va<span class="br0">)</span>, <a href="cpp-iterator-end.html"><span class="kw680">std::<span class="me2">end</span></span></a><span class="br0">(</span>va<span class="br0">)</span>, <span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">double</span> x<span class="br0">)</span> <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> <span class="st0">" "</span> <span class="sy1"><<</span> <a href="cpp-io-manip-left.html"><span class="kw1780">std::<span class="me2">right</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><span class="nu0">4</span><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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<span class="br0">}</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> <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">const</span> <span class="kw4">double</span> pi <span class="sy1">=</span> <a href="cpp-numeric-math-acos.html"><span class="kw1337">std::<span class="me2">acos</span></span></a><span class="br0">(</span><span class="sy2">-</span><span class="nu16">1.0</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// C++20: std::numbers::pi</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">auto</span> degrees_to_radians <span class="sy1">=</span> <span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">double</span> <span class="kw4">const</span><span class="sy3">&</span> x<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="br0">(</span>pi <span class="sy2">*</span> x <span class="sy2">/</span> <span class="nu0">180</span><span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">auto</span> radians_to_degrees <span class="sy1">=</span> <span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">double</span> <span class="kw4">const</span><span class="sy3">&</span> x<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="br0">(</span><span class="nu0">180</span> <span class="sy2">*</span> x <span class="sy2">/</span> pi<span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</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">double</span><span class="sy1">></span> degrees<span class="br0">{</span><span class="sy2">-</span><span class="nu0">90</span>, <span class="sy2">-</span><span class="nu0">60</span>, <span class="sy2">-</span><span class="nu0">45</span>, <span class="sy2">-</span><span class="nu0">30</span>, <span class="nu0">0</span>, <span class="nu0">30</span>, <span class="nu0">45</span>, <span class="nu0">60</span>, <span class="nu0">90</span><span class="br0">}</span><span class="sy4">;</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">double</span><span class="sy1">></span> radians <span class="sy1">=</span> degrees.<span class="me1">apply</span><span class="br0">(</span>degrees_to_radians<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>radians<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>radians<span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"(1)"</span>, <a href="cpp-numeric-math-atan2.html"><span class="kw1339">std::<span class="me2">atan2</span></span></a><span class="br0">(</span>sin, cos<span class="br0">)</span>.<span class="me1">apply</span><span class="br0">(</span>radians_to_degrees<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"(2)"</span>, <a href="cpp-numeric-math-atan2.html"><span class="kw1339">std::<span class="me2">atan2</span></span></a><span class="br0">(</span>sin<span class="sy2">/</span>cos, <span class="nu16">1.0</span><span class="br0">)</span>.<span class="me1">apply</span><span class="br0">(</span>radians_to_degrees<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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show<span class="br0">(</span><span class="st0">"(3)"</span>, <a href="cpp-numeric-math-atan2.html"><span class="kw1339">std::<span class="me2">atan2</span></span></a><span class="br0">(</span><span class="nu16">1.0</span>, cos<span class="sy2">/</span>sin<span class="br0">)</span>.<span class="me1">apply</span><span class="br0">(</span>radians_to_degrees<span class="br0">)</span><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">(1) -90° -60° -45° -30° 0° 30° 45° 60° 90°
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(2) -90° -60° -45° -30° 0° 30° 45° 60° 90°
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(3) 90° 120° 135° 150° 0° 30° 45° 60° 90°</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
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<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
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<table class="dsctable" style="font-size:0.8em">
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<tr>
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<th>DR</th>
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<th>应用于</th>
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<th>出版时的行为</th>
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<th>正确行为</th>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue3074">LWG 3074</a></td>
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<td>C++98</td>
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<td><span class="t-v">(2-3)</span> 从标量和 <code>valarray</code> 两者推导 <code>T</code> ，禁止混合类型的调用</td>
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<td>仅从 <code>valarray</code> 推导 <code>T</code></td>
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</tr>
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</table>
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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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<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-valarray-asin.html"><span class="t-lines"><span>asin<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-asin.html">std::asin</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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<td>
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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>
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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-valarray-atan.html"><span class="t-lines"><span>atan<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-atan.html">std::atan</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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-math-atan2.html"><span class="t-lines"><span>atan2</span><span>atan2f</span><span>atan2l</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>反正切，用符号确定象限<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-arg.html"><span class="t-lines"><span>arg</span></span></a></div>
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</div>
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</td>
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<td>返回辐角<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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</div>
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</div>
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</body>
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</html>
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