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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::counted_iterator&lt;I&gt;::</span>operator[]</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-iterator.html">iterator</a>&lrm; | <a href="cpp-iterator-counted_iterator.html">counted iterator</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> decltype<span class="br0">(</span><span class="kw4">auto</span><span class="br0">)</span> operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span> std<span class="sy4">::</span><span class="me2">iter_difference_t</span><span class="sy1">&lt;</span>I<span class="sy1">&gt;</span> n <span class="br0">)</span> <span class="kw4">const</span><br />
&nbsp; &nbsp; requires std<span class="sy4">::</span><span class="me2">random_access_iterator</span><span class="sy1">&lt;</span>I<span class="sy1">&gt;</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<p>&#35775;&#38382;&#20301;&#20110;&#32473;&#23450;&#20301;&#32622;&#30340;&#20803;&#32032;&#12290;&#33509; <code>n</code> &#19981;&#23567;&#20110;&#35760;&#24405;&#30340;&#21040;&#26411;&#23614;&#30340;&#36317;&#31163;&#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>n</td>
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<td>&#30456;&#23545;&#24403;&#21069;&#20301;&#32622;&#30340;&#20301;&#31227;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p><span class="t-c"><span class="mw-geshi cpp source-cpp">this<span class="sy2">-</span><span class="sy1">&gt;</span>base<span class="br0">(</span><span class="br0">)</span><span class="br0">[</span>n<span class="br0">]</span></span></span> &#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;iterator&gt;</span>
<span class="co2">#include &lt;array&gt;</span>
<span class="co2">#include &lt;list&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a> array<span class="br0">{</span><span class="st0">&#39;A&#39;</span>, <span class="st0">&#39;B&#39;</span>, <span class="st0">&#39;C&#39;</span>, <span class="st0">&#39;D&#39;</span>, <span class="st0">&#39;E&#39;</span><span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">counted_iterator</span> it<span class="br0">{</span> array.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">+</span> <span class="nu0">1</span>, <span class="coMULTI">/*count:*/</span> <span class="nu0">3</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> it.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> it<span class="br0">[</span>i<span class="br0">]</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> it.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span>
it<span class="br0">[</span>i<span class="br0">]</span> <span class="sy2">+</span><span class="sy1">=</span> <span class="br0">(</span><span class="st0">&#39;E&#39;</span> <span class="sy2">-</span> <span class="st0">&#39;A&#39;</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> it.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> it<span class="br0">[</span>i<span class="br0">]</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<a href="cpp-container-list.html"><span class="kw1275">std::<span class="me2">list</span></span></a> list <span class="br0">{</span><span class="st0">&#39;X&#39;</span>, <span class="st0">&#39;Y&#39;</span>, <span class="st0">&#39;Z&#39;</span>, <span class="st0">&#39;W&#39;</span><span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">counted_iterator</span> it2<span class="br0">{</span> list.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">3</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="co1">// char x = it2[0]; // &#38169;&#35823;&#65306;&#19981;&#28385;&#36275;&#35201;&#27714; `random_access_iterator`</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="sy2">*</span>it2 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span> <span class="co1">// OK</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">B C D
F G H
X</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-iterator-counted_iterator-operator*.html"><span class="t-lines"><span>operator*</span><span>operator-&gt;</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>&#35775;&#38382;&#34987;&#25351;&#21521;&#30340;&#20803;&#32032;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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