84 lines
6.9 KiB
HTML
84 lines
6.9 KiB
HTML
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<title>std::packaged_task<R(Args...)>::reset</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::packaged_task<R(Args...)>::</span>reset</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-thread.html">thread</a>‎ | <a href="cpp-thread-packaged_task.html">packaged task</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> reset<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<p>重置状态，抛弃先前执行的结果。构造共享状态。</p>
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<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this <span class="sy1">=</span> packaged_task<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>f<span class="br0">)</span><span class="br0">)</span></span></span> ，其中 <code>f</code> 是存储的任务。</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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<p>（无）</p>
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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>（无）</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<ul>
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<li>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 无共享状态则为 <span class="t-lc"><a href="cpp-thread-future_error.html">std::future_error</a></span> 。设置 error_condition 为 <a href="cpp-thread-future_errc.html"><tt>no_state</tt></a> 。</li>
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<li>若无足够内存以分配新的共享状态则为 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 。</li>
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<li>新 <code>packaged_task</code> 的<a href="cpp-thread-packaged_task-packaged_task.html">移动构造函数</a>所抛的任何异常</li>
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</ul>
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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="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <cmath></span>
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<span class="co2">#include <thread></span>
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<span class="co2">#include <future></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-thread-packaged_task.html"><span class="kw2183">std::<span class="me2">packaged_task</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="br0">(</span><span class="kw4">int</span>,<span class="kw4">int</span><span class="br0">)</span><span class="sy1">></span> task<span class="br0">(</span><span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">int</span> a, <span class="kw4">int</span> b<span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-numeric-math-pow.html"><span class="kw1332">std::<span class="me2">pow</span></span></a><span class="br0">(</span>a, b<span class="br0">)</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-thread-future.html"><span class="kw2180">std::<span class="me2">future</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> result <span class="sy1">=</span> task.<span class="me1">get_future</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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task<span class="br0">(</span><span class="nu0">2</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> <span class="st0">"2^9 = "</span> <span class="sy1"><<</span> result.<span class="me1">get</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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task.<span class="me1">reset</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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result <span class="sy1">=</span> task.<span class="me1">get_future</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-thread-thread.html"><span class="kw2146">std::<span class="me2">thread</span></span></a> task_td<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>task<span class="br0">)</span>, <span class="nu0">2</span>, <span class="nu0">10</span><span class="br0">)</span><span class="sy4">;</span>
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task_td.<span class="me1">join</span><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">"2^10 = "</span> <span class="sy1"><<</span> result.<span class="me1">get</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">2^9 = 512
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2^10 = 1024</pre></div>
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