255 lines
20 KiB
HTML
255 lines
20 KiB
HTML
<!DOCTYPE html>
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<title>std::ranges::move, std::ranges::move_result</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_ranges_move 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::ranges::</span>move, <span style="font-size:0.7em; line-height:130%">std::ranges::</span>move_result</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-algorithm.html">algorithm</a>‎ | <a href="cpp-algorithm-ranges.html">ranges</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-algorithm.html"><algorithm></a></code></div>
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<td></td>
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<div>调用签名</div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> std<span class="sy4">::</span><span class="me2">input_iterator</span> I, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I<span class="sy1">></span> S, std<span class="sy4">::</span><span class="me2">weakly_incrementable</span> O <span class="sy1">></span><br /></span>
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<p>requires std<span class="sy4">::</span><span class="me2">indirectly_movable</span><span class="sy1"><</span>I, O<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> move_result<span class="sy1"><</span>I, O<span class="sy1">></span><br /></p>
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move<span class="br0">(</span> I first, S last, O result <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> ranges<span class="sy4">::</span><span class="me2">input_range</span> R, std<span class="sy4">::</span><span class="me2">weakly_incrementable</span> O <span class="sy1">></span><br /></span>
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<p>requires std<span class="sy4">::</span><span class="me2">indirectly_movable</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>, O<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> move_result<span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>, O<span class="sy1">></span><br /></p>
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move<span class="br0">(</span> R<span class="sy3">&&</span> r, O result <span class="br0">)</span><span class="sy4">;</span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div>辅助类型</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> I, <span class="kw1">class</span> O <span class="sy1">></span><br />
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<span class="kw1">using</span> move_result <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">in_out_result</span><span class="sy1"><</span>I, O<span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div class="t-li1"><span class="t-li">1)</span> 赋值 <code>[first, last)</code> 所定义的范围重点元素到始于 <code>result</code> 的另一范围。 若 <code>result</code> 在范围 <code>[first, last)</code> 内则行为未定义。此情况下可能可以用 <span class="t-lc">ranges::move_backward</span> 代替。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ,但以 <code>r</code> 为源范围,如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 为 <code>first</code> 并以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 为 <code>last</code> 。</div>
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<p><i>被移动</i>的范围的元素将仍然含有适当类型的合法值,但不必为与移动前相同的值。</p>
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<p>此页面上描述的仿函数实体是 <i>niebloid</i> ,即:</p>
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<ul>
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<li>调用它们中的任何一者时不可指定显式模板实参。</li>
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<li>它们无一对<a href="cpp-language-adl.html">实参依赖查找</a>可见。</li>
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<li>在<a href="cpp-language-unqualified_lookup.html">通常无限定查找</a>寻找函数调用运算符左侧的名称找到它们之一时,它禁止<a href="cpp-language-adl.html">实参依赖查找</a>。</li>
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</ul>
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<p>实际上,它们能以函数对象,或以某些特殊编译器扩展实现。</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>first</td>
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<td>-</td>
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<td>要移动的元素范围的起始</td>
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</tr>
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<tr class="t-par">
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<td>last</td>
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<td>-</td>
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<td>要移动元素范围的末尾</td>
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</tr>
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<tr class="t-par">
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<td>r</td>
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<td>-</td>
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<td>要移动的元素范围</td>
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</tr>
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<tr class="t-par">
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<td>result</td>
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<td>-</td>
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<td>目标范围的起始</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">{</span>last, result <span class="sy2">+</span> N<span class="br0">}</span></span></span> ,其中</p>
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<div class="t-li1"><span class="t-li">1)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">N <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>first, last<span class="br0">)</span></span></span> ;</div>
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<div class="t-li1"><span class="t-li">2)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">N <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>r<span class="br0">)</span></span></span> 。</div>
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<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6_2">复杂度</span></h3>
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<p>准确赋值 <span class="t-c"><span class="mw-geshi cpp source-cpp">N</span></span> 次。</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>移动重叠的范围时, <code>ranges::move</code> 适合向左移动(目标范围的起始在源范围外),而 <span class="t-lc">ranges::move_backward</span> 适合向右移动(目标范围的末尾在源范围外)。</p>
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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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<table class="eq-fun-cpp-table">
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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="kw1">struct</span> move_fn <span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">input_iterator</span> I, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I<span class="sy1">></span> S, std<span class="sy4">::</span><span class="me2">weakly_incrementable</span> O<span class="sy1">></span>
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requires std<span class="sy4">::</span><span class="me2">indirectly_movable</span><span class="sy1"><</span>I, O<span class="sy1">></span>
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">move_result</span><span class="sy1"><</span>I, O<span class="sy1">></span>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span> I first, S last, O result <span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> first <span class="sy3">!</span><span class="sy1">=</span> last<span class="sy4">;</span> <span class="sy2">++</span>first, <span class="sy2">++</span>result<span class="br0">)</span>
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<span class="sy2">*</span>result <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">iter_move</span><span class="br0">(</span>first<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">return</span> <span class="br0">{</span>std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>first<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>result<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">input_range</span> R, std<span class="sy4">::</span><span class="me2">weakly_incrementable</span> O<span class="sy1">></span>
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requires std<span class="sy4">::</span><span class="me2">indirectly_movable</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>, O<span class="sy1">></span>
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">move_result</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">borrowed_iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span>, O<span class="sy1">></span>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span> R<span class="sy3">&&</span> r, O result <span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span><span class="br0">(</span>ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r<span class="br0">)</span>, ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>result<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">inline</span> <span class="kw4">constexpr</span> move_fn move<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></pre></div>
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</div>
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</td>
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</tr>
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</table>
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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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<p>以下代码从一个容器移动线程对象(它们自身<i>不可复制</i>)到另一容器。</p>
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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 <iostream></span>
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<span class="co2">#include <vector></span>
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<span class="co2">#include <list></span>
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<span class="co2">#include <iterator></span>
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<span class="co2">#include <thread></span>
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<span class="co2">#include <chrono></span>
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<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">::</span><span class="me2">chrono_literals</span><span class="sy4">;</span>
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<span class="kw4">void</span> f<span class="br0">(</span><a href="cpp-chrono-duration.html"><span class="kw996">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">milliseconds</span></span></a> n<span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-thread-sleep_for.html"><span class="kw2149">std::<span class="me2">this_thread</span><span class="sy4">::</span><span class="me2">sleep_for</span></span></a><span class="br0">(</span>n<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">"thread with n="</span> <span class="sy1"><<</span> n.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"ms ended"</span> <span class="sy1"><<</span> <a href="cpp-io-manip-endl.html"><span class="kw1791">std::<span class="me2">endl</span></span></a><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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<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">jthread</span><span class="sy1">></span> v<span class="sy4">;</span>
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v.<span class="me1">emplace_back</span><span class="br0">(</span>f, 400ms<span class="br0">)</span><span class="sy4">;</span>
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v.<span class="me1">emplace_back</span><span class="br0">(</span>f, 600ms<span class="br0">)</span><span class="sy4">;</span>
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v.<span class="me1">emplace_back</span><span class="br0">(</span>f, 800ms<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-container-list.html"><span class="kw1275">std::<span class="me2">list</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">jthread</span><span class="sy1">></span> l<span class="sy4">;</span>
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<span class="co1">// std::ranges::copy() 不能编译,因为 std::jthread 不可复制</span>
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std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>v, <a href="cpp-iterator-back_inserter.html"><span class="kw665">std::<span class="me2">back_inserter</span></span></a><span class="br0">(</span>l<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">thread with n=400ms ended
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thread with n=600ms ended
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thread with n=800ms ended</pre></div>
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</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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<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-algorithm-ranges-move_backward.html"><span class="t-lines"><span>ranges::move_backword</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>按从后往前的顺序移动某一范围的元素到新的位置<br />
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<span class="t-mark">(niebloid)</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-algorithm-ranges-copy.html"><span class="t-lines"><span>ranges::copy</span><span>ranges::copy_if</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><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>将某一范围的元素复制到一个新的位置<br />
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<span class="t-mark">(niebloid)</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-algorithm-ranges-copy_backward.html"><span class="t-lines"><span>ranges::copy_backward</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>按从后往前的顺序复制一个范围内的元素<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
|
|
<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-algorithm-move.html"><span class="t-lines"><span>move</span></span></a></div>
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<div><span class="t-lines"><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>将某一范围的元素移动到一个新的位置<br />
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<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-utility-move.html"><span class="t-lines"><span>move</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>获得右值引用<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<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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