67 lines
3.4 KiB
HTML
67 lines
3.4 KiB
HTML
<!DOCTYPE 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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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>std::basic_string_view<CharT,Traits>::front</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_basic_string_view_front skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_string_view<CharT,Traits>::</span>front</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-string.html">string</a>‎ | <a href="cpp-string-basic_string_view.html">basic string 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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<tr class="t-dcl t-since-cxx17">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> const_reference front<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-cxx17">(C++17 起)</span></td>
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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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<p>返回到视图首字符的引用。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">empty<span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> <span class="kw2">true</span></span></span> 则行为未定义。</p>
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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>到首字符的引用，等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="nu0">0</span><span class="br0">)</span></span></span> 。</p>
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<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
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<p>常数。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</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><a href="cpp-string-basic_string_view-back.html"><span class="t-lines"><span>back</span></span></a></div>
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</div>
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</td>
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<td>访问最末字符<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-basic_string_view-empty.html"><span class="t-lines"><span>empty</span></span></a></div>
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</div>
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</td>
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<td>检查视图是否为空<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</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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</body>
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</html>
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