85 lines
6.2 KiB
HTML
85 lines
6.2 KiB
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::ranges::common_view<V>::base</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_ranges_common_view_base 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::common_view<V>::</span>base</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-common_view.html">common view</a></span></div>
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<table class="t-dcl-begin">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> V base<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span><span class="sy3">&</span> requires std<span class="sy4">::</span><span class="me2">copy_constructible</span><span class="sy1"><</span>V<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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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> V base<span class="br0">(</span><span class="br0">)</span> <span class="sy3">&&</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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<td></td>
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<td></td>
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<p>返回底层视图的副本。</p>
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<div class="t-li1"><span class="t-li">1)</span> 从底层视图复制构造结果。</div>
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<div class="t-li1"><span class="t-li">2)</span> 从底层视图移动构造结果。</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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<p>（无）</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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<p>底层视图的副本。</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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<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 <iostream></span>
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<span class="co2">#include <ranges></span>
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<span class="co2">#include <string></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-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> str <span class="br0">{</span> <span class="st0">"C++20"</span> <span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">auto</span> view <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">views</span><span class="sy4">::</span><span class="me2">common</span><span class="br0">(</span>str<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> copy_of_str <span class="sy1">=</span> view.<span class="me1">base</span><span class="br0">(</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">"copy of str: ["</span> <span class="sy1"><<</span> copy_of_str <span class="sy1"><<</span> <span class="st0">"]<span class="es1">\n</span>"</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">"view.base(): ["</span> <span class="sy1"><<</span> view.<span class="me1">base</span><span class="br0">(</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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<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> move_str <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>view.<span class="me1">base</span><span class="br0">(</span><span class="br0">)</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">"moved str: ["</span> <span class="sy1"><<</span> move_str <span class="sy1"><<</span> <span class="st0">"]<span class="es1">\n</span>"</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">"view.base(): ["</span> <span class="sy1"><<</span> view.<span class="me1">base</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"]<span class="es1">\n</span>"</span><span class="sy4">;</span> <span class="co1">// 未指定</span>
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<span class="br0">}</span></pre></div>
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</div>
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<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">copy of str: [C++20]
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view.base(): [C++20]
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moved str: [C++20]
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view.base(): []</pre></div>
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