547 lines
36 KiB
HTML
547 lines
36 KiB
HTML
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<title>std::ranges::owning_view</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_ranges_owning_view skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ranges::</span>owning_view</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-ranges.html">ranges</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-ranges.html"><ranges></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">range</span> R<span class="sy1">></span><br /></span>
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<p> requires std<span class="sy4">::</span><span class="me2">movable</span><span class="sy1"><</span>R<span class="sy1">></span> <span class="sy3">&&</span> <span class="br0">(</span><span class="sy3">!</span><span class="coMULTI">/*is-initializer-list*/</span><span class="sy1"><</span>R<span class="sy1">></span><span class="br0">)</span><br /></p>
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<span class="kw1">class</span> owning_view <span class="sy4">:</span> <span class="kw1">public</span> ranges<span class="sy4">::</span><span class="me2">view_interface</span><span class="sy1"><</span>owning_view<span class="sy1"><</span>R<span class="sy1">>></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p><code>owning_view</code> 是拥有 <a href="cpp-ranges-range.html"><code>range</code></a> 的独占所有权的 <a href="cpp-ranges-view.html"><code>view</code></a> 。它为仅移动并在其内部存储该 <code>range</code> 。</p>
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<p>requires 子句中的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="coMULTI">/*is-initializer-list*/</span><span class="sy1"><</span>R<span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 当且仅当 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>R<span class="sy1">></span></span></span> 为 <span class="t-lc"><a href="cpp-utility-initializer_list.html">std::initializer_list</a></span> 的特化。</p>
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<h3><span class="mw-headline" id=".E6.95.B0.E6.8D.AE.E6.88.90.E5.91.98">数据成员</span></h3>
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<p><code>owning_view</code> 的典型实现仅拥有一个非静态数据成员： <code>R</code> 类型的底层范围。此处显示该成员为 <code><i>r_</i></code> （名字仅用于阐释）。</p>
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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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<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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</td>
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<td>通过值初始化或移动构造存储的范围构造 <code>owning_view</code><br />
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<span class="t-mark">(公开成员函数)</span></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>移动赋值存储的范围<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>base</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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</td>
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<td>返回到存储的范围的引用<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>begin</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>返回存储的范围的起始迭代器<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>end</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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</td>
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<td>返回存储的范围的哨位<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>empty</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>检查存储的范围是否为空<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div><span class="t-lines"><span>size</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>返回存储的 <a href="cpp-ranges-sized_range.html"><code>sized_range</code></a> 的大小<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>data</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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<td>返回指向存储的 <a href="cpp-ranges-contiguous_range.html"><code>contiguous_range</code></a> 起始的指针<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<h5><span class="mw-headline" id=".E7.BB.A7.E6.89.BF.E8.87.AA_std::ranges::view_interface">继承自 <span class="t-lc">std::ranges::view_interface</span></span></h5>
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<div><a href="cpp-ranges-view_interface-operator_bool.html"><span class="t-lines"><span>operator bool</span></span></a></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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<td>返回派生视图是否为非空。若 <span class="t-lc">ranges::empty</span> 可应用于它则提供。<br />
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<span class="t-mark">(<code>std::ranges::view_interface<D></code> 的公开成员函数)</span></td>
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<div><a href="cpp-ranges-view_interface-front.html"><span class="t-lines"><span>front</span></span></a></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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<td>返回派生视图中的首元素。若视图满足 <a href="cpp-ranges-forward_range.html"><code>forward_range</code></a> 则提供。<br />
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<span class="t-mark">(<code>std::ranges::view_interface<D></code> 的公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-ranges-view_interface-back.html"><span class="t-lines"><span>back</span></span></a></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>返回派生视图中的末元素。若视图满足 <a href="cpp-ranges-bidirectional_range.html"><code>bidirectional_range</code></a> 与 <a href="cpp-ranges-common_range.html"><code>common_range</code></a> 则提供。<br />
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<span class="t-mark">(<code>std::ranges::view_interface<D></code> 的公开成员函数)</span></td>
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</tr>
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<div class="t-dsc-member-div">
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<div><a href="cpp-ranges-view_interface-operator_at.html"><span class="t-lines"><span>operator[]</span></span></a></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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<td>返回派生视图中的第 n 个元素。若视图满足 <a href="cpp-ranges-random_access_range.html"><code>random_access_range</code></a> 则提供。<br />
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<span class="t-mark">(<code>std::ranges::view_interface<D></code> 的公开成员函数)</span></td>
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<div class="t-member">
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<h2><span class="mw-headline" id="std::ranges::owning_view::owning_view"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>owning_view</span></h2>
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<div><span class="mw-geshi cpp source-cpp">owning_view<span class="br0">(</span><span class="br0">)</span> requires std<span class="sy4">::</span><span class="me2">default_initializable</span><span class="sy1"><</span>R<span class="sy1">></span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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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">owning_view<span class="br0">(</span> owning_view<span class="sy3">&&</span> other <span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">default</span><span class="sy4">;</span></span></div>
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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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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> owning_view<span class="br0">(</span> R<span class="sy3">&&</span> t <span class="br0">)</span><span class="sy4">;</span></span></div>
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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 t-since-cxx20">
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<div><span class="mw-geshi cpp source-cpp">owning_view<span class="br0">(</span> <span class="kw4">const</span> owning_view<span class="sy3">&</span> <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
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<td>(4)</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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<div class="t-li1"><span class="t-li">1)</span> 默认构造函数。由其默认成员初始化器（<span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy1">=</span> R<span class="br0">(</span><span class="br0">)</span></span></span>）值初始化存储的范围。</div>
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<div class="t-li1"><span class="t-li">2)</span> 复制构造函数。从 <code>other</code> 的存储范围移动构造存储范围。</div>
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<div class="t-li1"><span class="t-li">3)</span> 从 <code>t</code> 移动构造存储范围。</div>
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<div class="t-li1"><span class="t-li">4)</span> 复制构造函数被删除。 <code>owning_view</code> 为仅移动。</div>
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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>other</td>
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<td>-</td>
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<td>要移动的 <code>owning_view</code></td>
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</tr>
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<tr class="t-par">
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<td>t</td>
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<td>-</td>
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<td>要移动的范围</td>
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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::owning_view::operator.3D"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>operator=</span></h2>
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<div><span class="mw-geshi cpp source-cpp">owning_view<span class="sy3">&</span> opeartor<span class="sy1">=</span><span class="br0">(</span> owning_view<span class="sy3">&&</span> other <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>(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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<div><span class="mw-geshi cpp source-cpp">owning_view<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> owning_view<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-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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<div class="t-li1"><span class="t-li">1)</span> 移动赋值运算符。从 <code>other</code> 的存储范围移动赋值存储范围。</div>
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<div class="t-li1"><span class="t-li">2)</span> 复制赋值运算符被删除。 <code>owning_view</code> 为仅移动。</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0_2">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>other</td>
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<td>-</td>
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<td>要移动的另一 <code>owning_view</code></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><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 。</p>
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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::owning_view::base"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>base</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> R<span class="sy3">&</span> base<span class="br0">(</span><span class="br0">)</span> <span class="sy3">&</span> <span class="kw1">noexcept</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">constexpr</span> <span class="kw4">const</span> R<span class="sy3">&</span> base<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="sy3">&</span> <span class="kw1">noexcept</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 t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> R<span class="sy3">&&</span> base<span class="br0">(</span><span class="br0">)</span> <span class="sy3">&&</span> <span class="kw1">noexcept</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 t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">const</span> R<span class="sy3">&&</span> base<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="sy3">&&</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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</td>
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<td>(4)</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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<p>返回到存储的范围的引用，保持值类别与 const 限定。</p>
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<div class="t-li1"><span class="t-li">1-2)</span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> r_<span class="sy4">;</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">3-4)</span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</span></span></span> 。</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::owning_view::begin"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>begin</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"><span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R<span class="sy1">></span> begin<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">constexpr</span> <span class="kw4">auto</span> begin<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> requires ranges<span class="sy4">::</span><span class="me2">range</span><span class="sy1"><</span><span class="kw4">const</span> R<span class="sy1">></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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<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</span></span></span> 。</p>
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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::owning_view::end"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>end</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"><span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">sentinel_t</span><span class="sy1"><</span>R<span class="sy1">></span> end<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">constexpr</span> <span class="kw4">auto</span> end<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> requires ranges<span class="sy4">::</span><span class="me2">range</span><span class="sy1"><</span><span class="kw4">const</span> R<span class="sy1">></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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<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</span></span></span> 。</p>
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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::owning_view::empty"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>empty</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"><span class="kw4">constexpr</span> <span class="kw4">bool</span> empty<span class="br0">(</span><span class="br0">)</span> requires requires <span class="br0">{</span> ranges<span class="sy4">::</span><span class="me2">empty</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</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">constexpr</span> <span class="kw4">bool</span> empty<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> requires requires <span class="br0">{</span> ranges<span class="sy4">::</span><span class="me2">empty</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</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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</tr>
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</tbody>
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</table>
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<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> ranges<span class="sy4">::</span><span class="me2">empty</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</span></span></span> 。</p>
|
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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::owning_view::size"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>size</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"><span class="kw4">constexpr</span> <span class="kw4">auto</span> size<span class="br0">(</span><span class="br0">)</span> requires ranges<span class="sy4">::</span><span class="me2">sized_range</span><span class="sy1"><</span>R<span class="sy1">></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>
|
|
<tr class="t-dcl t-since-cxx20">
|
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<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">auto</span> size<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> requires ranges<span class="sy4">::</span><span class="me2">sized_range</span><span class="sy1"><</span><span class="kw4">const</span> R<span class="sy1">></span><span class="sy4">;</span></span></div>
|
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</td>
|
|
<td>(2)</td>
|
|
<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">
|
|
<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>
|
|
<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> ranges<span class="sy4">::</span><span class="me2">size</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</span></span></span> 。</p>
|
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</div>
|
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<div class="t-member">
|
|
<h2><span class="mw-headline" id="std::ranges::owning_view::data"><span style="font-size:0.7em; line-height:130%">std::ranges::owning_view::</span>data</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"><span class="kw4">constexpr</span> <span class="kw4">auto</span> data<span class="br0">(</span><span class="br0">)</span> requires ranges<span class="sy4">::</span><span class="me2">contiguous_range</span><span class="sy1"><</span>R<span class="sy1">></span><span class="sy4">;</span></span></div>
|
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</td>
|
|
<td>(1)</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<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">constexpr</span> <span class="kw4">auto</span> data<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> requires ranges<span class="sy4">::</span><span class="me2">contiguous_range</span><span class="sy1"><</span><span class="kw4">const</span> R<span class="sy1">></span><span class="sy4">;</span></span></div>
|
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</td>
|
|
<td>(2)</td>
|
|
<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">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
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</tr>
|
|
</tbody>
|
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</table>
|
|
<p>等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> ranges<span class="sy4">::</span><span class="me2">data</span><span class="br0">(</span>r_<span class="br0">)</span><span class="sy4">;</span></span></span> 。</p>
|
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</div>
|
|
<h3><span class="mw-headline" id=".E8.BE.85.E5.8A.A9.E6.A8.A1.E6.9D.BF">辅助模板</span></h3>
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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"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> T<span class="sy1">></span><br /></span>
|
|
<p><span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> enable_borrowed_range<span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">owning_view</span><span class="sy1"><</span>T<span class="sy1">>></span> <span class="sy1">=</span><br /></p>
|
|
std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">enable_borrowed_range</span><span class="sy1"><</span>T<span class="sy1">></span><span class="sy4">;</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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</tr>
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</tbody>
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</table>
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<p><a href="cpp-ranges-borrowed_range.html"><tt>std::ranges::enable_borrowed_range</tt></a> 的此特化使得 <code>owning_view</code> 在底层范围满足 <a href="cpp-ranges-borrowed_range.html"><code>borrowed_range</code></a> 时满足它。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <ranges></span>
|
|
<span class="co2">#include <string></span>
|
|
<span class="co2">#include <cassert></span>
|
|
<span class="co2">#include <iostream></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">owning_view</span> ov<span class="br0">{</span> <span class="st0">"cosmos"</span>s <span class="br0">}</span><span class="sy4">;</span> <span class="co1">// 推导的 R 类型为 std::string ；</span>
|
|
<span class="co1">// `ov` 为此字符串的唯一所有者</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>
|
|
<span class="sy1"><<</span> <a href="cpp-io-manip-boolalpha.html"><span class="kw1764">std::<span class="me2">boolalpha</span></span></a>
|
|
<span class="sy1"><<</span> <span class="st0">"call empty() : "</span> <span class="sy1"><<</span> ov.<span class="me1">empty</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
|
|
<span class="sy1"><<</span> <span class="st0">"call size() : "</span> <span class="sy1"><<</span> ov.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
|
|
<span class="sy1"><<</span> <span class="st0">"call front() : "</span> <span class="sy1"><<</span> ov.<span class="me1">front</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span> <span class="co1">// 同 *(ov.begin())</span>
|
|
<span class="sy1"><<</span> <span class="st0">"call back() : "</span> <span class="sy1"><<</span> ov.<span class="me1">back</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span> <span class="co1">// 等于 *(ov.end()-1)</span>
|
|
<span class="sy1"><<</span> <span class="st0">"call data() : "</span> <span class="sy1"><<</span> ov.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
|
|
<span class="sy1"><<</span> <span class="st0">"call base() : "</span> <span class="sy1"><<</span> ov.<span class="me1">base</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span> <span class="co1">// ~> ov.size()</span>
|
|
<span class="sy1"><<</span> <span class="st0">"sizeof(ov) : "</span> <span class="sy1"><<</span> sizeof<span class="br0">(</span>ov<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span> <span class="co1">// 常等于 sizeof(R)</span>
|
|
<span class="sy1"><<</span> <span class="st0">"range-for : <span class="es1">\"</span>"</span><span class="sy4">;</span>
|
|
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span> c<span class="sy4">:</span> ov<span class="br0">)</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> c<span class="sy4">;</span>
|
|
<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">\"</span><span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
|
|
std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">owning_view</span><span class="sy1"><</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="sy1">></span> ov2<span class="sy4">;</span>
|
|
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>ov2.<span class="me1">empty</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="co1">// ov2 = ov; // 编译时错误：复制赋值运算符被删除</span>
|
|
ov2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>ov<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK</span>
|
|
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>ov.<span class="me1">empty</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-error-assert.html"><span class="kw774">assert</span></a><span class="br0">(</span>ov2.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> <span class="nu0">6</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>可能的输出：</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">call empty() : false
|
|
call size() : 6
|
|
call front() : c
|
|
call back() : s
|
|
call data() : cosmos
|
|
call base() : 6
|
|
sizeof(ov) : 32
|
|
range-for : "cosmos"</pre></div>
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</div>
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|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-ranges-ref_view.html"><span class="t-lines"><span>ranges::ref_view</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>某个其他 <a href="cpp-ranges-range.html"><code>range</code></a> 的元素的 <a href="cpp-ranges-view.html"><code>view</code></a><br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-ranges-all_view.html"><span class="t-lines"><span>views::all_t</span><span>views::all</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>包含 <a href="cpp-ranges-range.html"><code>range</code></a> 的所有元素的 <a href="cpp-ranges-view.html"><code>view</code></a><br />
|
|
<span class="t-mark">(别名模板)</span> <span class="t-mark">(范围适配器对象)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
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