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<title>std::reverse_iterator&lt;Iter&gt;::operator[]</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::reverse_iterator&lt;Iter&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-reverse_iterator.html">reverse iterator</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*unspecified*/</span> operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span> difference_type n <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx17">(C++17 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="coMULTI">/*unspecified*/</span> operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span> difference_type n <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p>&#36820;&#22238;&#22312;&#25351;&#23450;&#30456;&#30456;&#23545;&#20301;&#32622;&#30340;&#24341;&#29992;&#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;&#20110;&#24403;&#21069;&#20301;&#32622;&#30340;&#20301;&#32622;&#12290;</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>&#21040;&#22312;&#30456;&#23545;&#20301;&#32622;&#30340;&#20803;&#32032;&#30340;&#24341;&#29992;&#65292;&#21363; <span class="t-c"><span class="mw-geshi cpp source-cpp">base<span class="br0">(</span><span class="br0">)</span><span class="br0">[</span><span class="sy2">-</span>n<span class="sy2">-</span><span class="nu0">1</span><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;array&gt;</span>
<span class="co2">#include &lt;cstddef&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;iterator&gt;</span>
<span class="co2">#include &lt;list&gt;</span>
<span class="co2">#include &lt;vector&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="br0">{</span>
<span class="kw4">int</span> a<span class="br0">[</span><span class="br0">]</span><span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-iterator-reverse_iterator.html"><span class="kw658">std::<span class="me2">reverse_iterator</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy2">*</span><span class="sy1">&gt;</span> iter<span class="br0">{</span><a href="cpp-iterator-rbegin.html"><span class="kw678">std::<span class="me2">rbegin</span></span></a><span class="br0">(</span>a<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> i<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> <a href="cpp-iterator-size.html"><span class="kw684">std::<span class="me2">size</span></span></a><span class="br0">(</span>a<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> iter<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> <span class="co1">// decltype(iter[i]) &#20026; `int&amp;`</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="br0">}</span>
<span class="br0">{</span>
<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a> v<span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-iterator-reverse_iterator.html"><span class="kw658">std::<span class="me2">reverse_iterator</span></span></a><span class="sy1">&lt;</span><a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">iterator</span><span class="sy1">&gt;</span> iter<span class="br0">{</span><a href="cpp-iterator-rbegin.html"><span class="kw678">std::<span class="me2">rbegin</span></span></a><span class="br0">(</span>v<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> i<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> i <span class="sy3">!</span><span class="sy1">=</span> <a href="cpp-iterator-size.html"><span class="kw684">std::<span class="me2">size</span></span></a><span class="br0">(</span>v<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> iter<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> <span class="co1">// decltype(iter[i]) &#20026; `int&amp;`</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="br0">}</span>
<span class="br0">{</span>
<span class="co1">// constexpr context</span>
<span class="kw4">constexpr</span> <span class="kw4">static</span> <a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="nu0">4</span><span class="sy1">&gt;</span> z<span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">constexpr</span> <a href="cpp-iterator-reverse_iterator.html"><span class="kw658">std::<span class="me2">reverse_iterator</span></span></a><span class="sy1">&lt;</span>decltype<span class="br0">(</span>z<span class="br0">)</span><span class="sy4">::</span><span class="me2">const_iterator</span><span class="sy1">&gt;</span> it<span class="br0">{</span><a href="cpp-iterator-rbegin.html"><span class="kw679">std::<span class="me2">crbegin</span></span></a><span class="br0">(</span>z<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
static_assert<span class="br0">(</span>it<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span> <span class="sy1">==</span> <span class="nu0">2</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">{</span>
<a href="cpp-container-list.html"><span class="kw1275">std::<span class="me2">list</span></span></a> li<span class="br0">{</span><span class="nu0">0</span>, <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span><span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-iterator-reverse_iterator.html"><span class="kw658">std::<span class="me2">reverse_iterator</span></span></a><span class="sy1">&lt;</span><a href="cpp-container-list.html"><span class="kw1275">std::<span class="me2">list</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">iterator</span><span class="sy1">&gt;</span> iter<span class="br0">{</span><a href="cpp-iterator-rbegin.html"><span class="kw678">std::<span class="me2">rbegin</span></span></a><span class="br0">(</span>li<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
<span class="sy2">*</span>iter <span class="sy1">=</span> <span class="nu0">42</span><span class="sy4">;</span> <span class="co1">// OK</span>
<span class="co1">// iter[0] = 13; // &#32534;&#35793;&#38169;&#35823; ~ &#24213;&#23618;&#36845;&#20195;&#22120;&#19981;&#23454;&#29616;&#38543;&#26426;&#35775;&#38382;&#36845;&#20195;&#22120;</span>
<span class="br0">}</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">3 2 1 0
3 2 1 0</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-reverse_iterator-operator*.html"><span class="t-lines"><span>operator*</span><span>operator-&gt;</span></span></a></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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