107 lines
6.7 KiB
HTML
107 lines
6.7 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::deque<T,Allocator>::operator[]</title>
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_container_deque_operator_at skin-cppreference2 action-view cpp-page-template cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::deque<T,Allocator>::</span>operator[]</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-container.html">container</a>‎ | <a href="cpp-container-deque.html">deque</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<div class="t-page-template" style="">
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<p></p>
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</div>
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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dcl t-since-cxx98">
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<td class="t-dcl-nopad">
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<div><span class="mw-geshi cpp source-cpp">reference operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span> size_type pos <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<tr class="t-dcl t-since-cxx98">
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<td class="t-dcl-nopad">
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<div><span class="mw-geshi cpp source-cpp">const_reference operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span> size_type pos <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td class="t-dcl-nopad"></td>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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</table>
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<p>返回位于指定位置 <code>pos</code> 的元素的引用。不进行边界检查。</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>pos</td>
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<td>-</td>
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<td>要返回的元素的位置</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>到所需元素的引用。</p>
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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>常数。</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>不同于 <span class="t-lc"><a href="cpp-container-map-operator_at.html">std::map::operator[]</a></span> ，此运算符决不插入新元素到容器。通过此运算符访问不存在的元素是未定义行为。</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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<p>下列代码使用 <code>operator[]</code> 读取并写入 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-container-deque.html"><span class="kw1271">std::<span class="me2">deque</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span></span></span> ：</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 <deque></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-container-deque.html"><span class="kw1271">std::<span class="me2">deque</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> numbers <span class="br0">{</span><span class="nu0">2</span>, <span class="nu0">4</span>, <span class="nu0">6</span>, <span class="nu0">8</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">"Second element: "</span> <span class="sy1"><<</span> numbers<span class="br0">[</span><span class="nu0">1</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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numbers<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span> <span class="sy1">=</span> <span class="nu0">5</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">"All numbers:"</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">auto</span> i <span class="sy4">:</span> numbers<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> i<span class="sy4">;</span>
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<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 class="es1">\n</span>'</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">Second element: 4
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All numbers: 5 4 6 8</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-container-deque-at.html"><span class="t-lines"><span>at</span></span></a></div>
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</div>
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</td>
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<td>访问指定的元素，同时进行越界检查<br />
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<span class="t-mark">(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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</div>
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</div>
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</body>
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</html>
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