268 lines
15 KiB
HTML
268 lines
15 KiB
HTML
<!DOCTYPE html>
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<title>std::ranges::basic_istream_view::iterator</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_ranges_basic_istream_view_iterator skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ranges::basic_istream_view::</span><i>iterator</i></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-ranges.html">ranges</a>‎ | <a href="cpp-ranges-basic_istream_view.html">basic istream view</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><span class="mw-geshi cpp source-cpp"><span class="kw1">struct</span> <span class="coMULTI">/*iterator*/</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<td></td>
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<td></td>
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<p><code>basic_istream_view::begin</code> 的返回类型。此处展示的名字 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span></span></span> 仅用于阐释。</p>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span></span></span> 为 <a href="cpp-iterator-input_iterator.html"><code>input_iterator</code></a> ，但不满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> ，从而无法用于 C++20 前的<a href="cpp-algorithm.html">算法</a>。</p>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc-hitem">
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<td>成员类型</td>
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<td>定义</td>
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<tr class="t-dsc">
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<td><code>iterator_concept</code><span class="t-mark-rev t-since-cxx20">(C++20)</span></td>
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<td><span class="t-lc"><a href="cpp-iterator-iterator_tags.html">std::input_iterator_tag</a></span></td>
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</tr>
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<tr class="t-dsc">
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<td><code>difference_type</code><span class="t-mark-rev t-since-cxx20">(C++20)</span></td>
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<td><span class="t-lc"><a href="cpp-types-ptrdiff_t.html">std::ptrdiff_t</a></span></td>
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</tr>
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<tr class="t-dsc">
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<td><code>value_type</code><span class="t-mark-rev t-since-cxx20">(C++20)</span></td>
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<td><code>Val</code></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><span class="t-lines"><span>(构造函数)</span></span></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>构造迭代器<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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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>operator=</span></span></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>复制赋值运算符被删除； <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span></span></span> 为仅移动<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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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>operator++</span></span></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>令迭代器前进<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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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>operator*</span></span></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>返回当前元素<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 class="t-member">
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<h2><span class="mw-headline" id="std::ranges::basic_istream_view::iterator::iterator"><span style="font-size:0.7em; line-height:130%">std::ranges::basic_istream_view::<i>iterator</i>::</span><i>iterator</i></span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw1">explicit</span> <span class="coMULTI">/*iterator*/</span><span class="br0">(</span> basic_istream_view<span class="sy3">&</span> parent <span class="br0">)</span><span class="sy4">;</span></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="coMULTI">/*iterator*/</span><span class="br0">(</span> <span class="kw4">const</span> <span class="coMULTI">/*iterator*/</span><span class="sy3">&</span> <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
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</td>
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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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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span><span class="br0">(</span> <span class="coMULTI">/*iterator*/</span><span class="sy3">&&</span> <span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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</td>
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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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</tr>
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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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<div class="t-li1"><span class="t-li">1)</span> 从亲 <code>basic_istream_view</code> 构造迭代器。</div>
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<div class="t-li1"><span class="t-li">2)</span> 复制构造函数被删除。迭代器不可复制。</div>
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<div class="t-li1"><span class="t-li">3)</span> 移动构造函数被默认化。迭代器可移动。</div>
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</div>
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<div class="t-member">
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<h2><span class="mw-headline" id="std::ranges::basic_istream_view::iterator::operator.3D"><span style="font-size:0.7em; line-height:130%">std::ranges::basic_istream_view::<i>iterator</i>::</span>operator=</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span><span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> <span class="coMULTI">/*iterator*/</span><span class="sy3">&</span> <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></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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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span><span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="coMULTI">/*iterator*/</span><span class="sy3">&&</span> <span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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</td>
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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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</tr>
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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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<div class="t-li1"><span class="t-li">1)</span> 复制赋值运算符被删除。迭代器不可复制。</div>
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<div class="t-li1"><span class="t-li">2)</span> 移动赋值运算符被默认化。迭代器可移动。</div>
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</div>
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<div class="t-member">
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<h2><span class="mw-headline" id="std::ranges::basic_istream_view::iterator::operator.2B.2B"><span style="font-size:0.7em; line-height:130%">std::ranges::basic_istream_view::<i>iterator</i>::</span>operator++</span></h2>
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<table class="t-dcl-begin">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*iterator*/</span><span class="sy3">&</span> operator<span class="sy2">++</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></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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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> operator<span class="sy2">++</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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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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</tr>
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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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</table>
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<p>从底层流读取值并将它存储于亲 <code>basic_istream_view</code> 。</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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<div class="t-li1"><span class="t-li">1)</span> <code>*this</code></div>
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<div class="t-li1"><span class="t-li">2)</span> （无）</div>
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</div>
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<div class="t-member">
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<h2><span class="mw-headline" id="std::ranges::basic_istream_view::iterator::operator.2A"><span style="font-size:0.7em; line-height:130%">std::ranges::basic_istream_view::<i>iterator</i>::</span>operator*</span></h2>
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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">Val<span class="sy3">&</span> operator<span class="sy2">*</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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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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</tbody>
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</table>
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<p>返回到存储值的引用。</p>
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</div>
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<h3><span class="mw-headline" id=".E9.9D.9E.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">非成员函数</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>operator==</span></span></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>与 <span class="t-lc">std::default_sentinel_t</span> 比较<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 class="t-member">
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<h2><span class="mw-headline" id="operator.3D.3D.28std::ranges::basic_istream_view::iterator.2C_std::default_sentinel.29">operator==<span style="font-size:0.7em; line-height:130%">(std::ranges::basic_istream_view::<i>iterator</i>, std::default_sentinel)</span></span></h2>
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<table class="t-dcl-begin">
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<tr class="t-dcl t-since-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">friend</span> <span class="kw4">bool</span> operator<span class="sy1">==</span><span class="br0">(</span> <span class="kw4">const</span> <span class="coMULTI">/*iterator*/</span><span class="sy3">&</span> x, std<span class="sy4">::</span><span class="me2">default_sentinel_t</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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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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</tbody>
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</table>
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<p>与 <code>std::default_sentinel_t</code> 比较。</p>
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<p>若 <code>*this</code> 无亲 <code>basic_istream_view</code> 或若底层流发生错误则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 。</p>
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<p>此函数对通常<a href="cpp-language-unqualified_lookup.html">无限定</a>或<a href="cpp-language-qualified_lookup.html">有限定查找</a>不可见，而只能在 <code>std::ranges::basic_istream_view::<i>iterator</i></code> 为参数的关联类时由<a href="cpp-language-adl.html">实参依赖查找</a>找到。</p>
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</div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
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<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
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<table class="dsctable" style="font-size:0.8em">
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<tr>
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<th>DR</th>
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<th>应用于</th>
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<th>出版时的行为</th>
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<th>正确行为</th>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://wg21.link/P2325R3">P2325R3</a></td>
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<td>C++20</td>
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<td>因为 C++20 迭代器必须为 <a href="cpp-concepts-default_initializable.html"><code>default_initializable</code></a> 提供了默认构造函数</td>
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<td>与该要求一同移除</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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