603 lines
34 KiB
HTML
603 lines
34 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</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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</head>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_basic_string_view 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::</span>basic_string_view</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></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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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-string_view.html"><string_view></a></code></div>
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</td>
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<td></td>
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<td></td>
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</tr>
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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="kw1">template</span><span class="sy1"><</span><br /></span>
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<p> <span class="kw1">class</span> CharT,<br />
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<span class="kw1">class</span> Traits <span class="sy1">=</span> <a href="cpp-string-char_traits.html"><span class="kw1262">std::<span class="me2">char_traits</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span><br /></p>
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<span class="sy1">></span> <span class="kw1">class</span> basic_string_view<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-cxx17">(C++17 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>类模板 <code>basic_string_view</code> 描述一个能指代常量连续仿 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span> 对象序列的对象，序列首元素在零位置。</p>
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<table class="t-rev-begin">
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<tr class="t-rev t-since-cxx23">
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<td>
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<p><code>std::basic_string_view</code> 的每个特化均为<a href="cpp-named_req-TriviallyCopyable.html"><span style="font-style:italic">可平凡复制</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TriviallyCopyable)</span></a> 类型。</p>
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</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</span></td>
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</tr>
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</table>
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<p>典型的实现仅保有二个成员：指向常 <code>CharT</code> 的指针和大小。</p>
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<p>提供数种对常用字符类型的 typedef ：</p>
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<table class="t-dsc-begin">
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<tr class="t-dsc-header">
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<td colspan="2">
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<div>定义于头文件 <code><a href="cpp-header-string_view.html"><string_view></a></code></div>
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</td>
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</tr>
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<tr class="t-dsc-hitem">
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<td>类型</td>
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<td>定义</td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::string_view</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::wstring_view</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span><span class="kw4">wchar_t</span><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc">std::u8string_view</span> <span class="t-mark-rev t-since-cxx20">(C++20)</span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span>char8_t<span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::u16string_view</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span><span class="kw4">char16_t</span><span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><span class="t-lc"><strong class="selflink">std::u32string_view</strong></span></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span><span class="kw4">char32_t</span><span class="sy1">></span></span></span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.A8.A1.E6.9D.BF.E5.BD.A2.E5.8F.82">模板形参</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>CharT</td>
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<td>-</td>
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<td>字符类型</td>
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</tr>
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<tr class="t-par">
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<td>Traits</td>
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<td>-</td>
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<td>指定字符类型上操作的<a href="cpp-named_req-CharTraits.html"><span style="font-style:italic">字符特征</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CharTraits)</span></a> 类。同 <code>basic_string</code> ， <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">char_type</span></span></span> 必须指名同 <span class="t-c"><span class="mw-geshi cpp source-cpp">CharT</span></span> 的类型，否则程序为谬构。</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.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>
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<tr class="t-dsc">
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<td><code>traits_type</code></td>
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<td><code>Traits</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>value_type</code></td>
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<td><code>CharT</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>pointer</code></td>
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<td><code>CharT*</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>const_pointer</code></td>
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<td><code>const CharT*</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>reference</code></td>
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<td><code>CharT&</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>const_reference</code></td>
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<td><code>const CharT&</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>const_iterator</code></td>
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<td>实现定义的常<a href="cpp-named_req-RandomAccessIterator.html"><span style="font-style:italic">老式随机访问迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyRandomAccessIterator)</span></a> <span class="t-rev-inl t-since-cxx20"><span>、<a href="cpp-named_req-ConstexprIterator.html"><span style="font-style:italic">常量表达式迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(ConstexprIterator)</span></a></span> <span><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></span>兼<a href="cpp-named_req-ContiguousIterator.html"><span style="font-style:italic">老式连续迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyContiguousIterator)</span></a> ，其 <code>value_type</code> 为 <code>CharT</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>iterator</code></td>
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<td><code>const_iterator</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>const_reverse_iterator</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-reverse_iterator.html"><span class="kw658">std::<span class="me2">reverse_iterator</span></span></a><span class="sy1"><</span>const_iterator<span class="sy1">></span></span></span></td>
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</tr>
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<tr class="t-dsc">
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<td><code>reverse_iterator</code></td>
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<td><code>const_reverse_iterator</code></td>
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</tr>
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<tr class="t-dsc">
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<td><code>size_type</code></td>
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<td><span class="t-lc"><a href="cpp-types-size_t.html">std::size_t</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></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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</table>
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<p>注解： <code>iterator</code> 与 <code>const_iterator</code> 是同一类型，因为 <code>string_view</code> 是到常字符序列中的视图。</p>
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<p><a href="cpp-named_req-Container.html"><span style="font-style:italic">容器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Container)</span></a> 的迭代器类型上的所有要求亦应用于 <code>basic_string_view</code> 的 <code>iterator</code> 和 <code>const_iterator</code> 类型。</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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<table class="t-dsc-begin">
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<tr class="t-dsc">
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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><a href="cpp-string-basic_string_view-basic_string_view.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造 <code>basic_string_view</code><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><a href="cpp-string-basic_string_view-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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</td>
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<td>对视图赋值<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>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E8.BF.AD.E4.BB.A3.E5.99.A8">迭代器</span></h5>
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</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><a href="cpp-string-basic_string_view-begin.html"><span class="t-lines"><span>begin</span><span>cbegin</span></span></a></div>
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</div>
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</td>
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<td>返回指向起始位置的迭代器<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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<tr class="t-dsc">
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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-end.html"><span class="t-lines"><span>end</span><span>cend</span></span></a></div>
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</div>
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</td>
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<td>返回指向结尾的迭代器<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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<tr class="t-dsc">
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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-rbegin.html"><span class="t-lines"><span>rbegin</span><span>crbegin</span></span></a></div>
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</div>
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</td>
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<td>返回指向起始的反向迭代器<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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<tr class="t-dsc">
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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-rend.html"><span class="t-lines"><span>rend</span><span>crend</span></span></a></div>
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</div>
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</td>
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<td>返回指向结尾的反向迭代器<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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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E5.85.83.E7.B4.A0.E8.AE.BF.E9.97.AE">元素访问</span></h5>
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</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><a href="cpp-string-basic_string_view-operator_at.html"><span class="t-lines"><span>operator[]</span></span></a></div>
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</div>
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</td>
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<td>访问指定字符<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><a href="cpp-string-basic_string_view-at.html"><span class="t-lines"><span>at</span></span></a></div>
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</div>
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</td>
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<td>访问指定字符，带有边界检查<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><a href="cpp-string-basic_string_view-front.html"><span class="t-lines"><span>front</span></span></a></div>
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</div>
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</td>
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<td>访问首个字符<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><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>
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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><a href="cpp-string-basic_string_view-data.html"><span class="t-lines"><span>data</span></span></a></div>
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</div>
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</td>
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<td>返回指向视图首字符的指针<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>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E5.AE.B9.E9.87.8F">容量</span></h5>
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</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><a href="cpp-string-basic_string_view-size.html"><span class="t-lines"><span>size</span><span>length</span></span></a></div>
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</div>
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</td>
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<td>返回字符数<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><a href="cpp-string-basic_string_view-max_size.html"><span class="t-lines"><span>max_size</span></span></a></div>
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</div>
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</td>
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<td>返回最大字符数<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><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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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E4.BF.AE.E6.94.B9.E5.99.A8">修改器</span></h5>
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</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><a href="cpp-string-basic_string_view-remove_prefix.html"><span class="t-lines"><span>remove_prefix</span></span></a></div>
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</div>
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</td>
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<td>以后移起点收缩视图<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><a href="cpp-string-basic_string_view-remove_suffix.html"><span class="t-lines"><span>remove_suffix</span></span></a></div>
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</div>
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</td>
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<td>以前移终点收缩视图<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><a href="cpp-string-basic_string_view-swap.html"><span class="t-lines"><span>swap</span></span></a></div>
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</div>
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</td>
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<td>交换内容<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">
|
|
<h5><span class="mw-headline" id=".E6.93.8D.E4.BD.9C">操作</span></h5>
|
|
</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-copy.html"><span class="t-lines"><span>copy</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>复制字符<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-substr.html"><span class="t-lines"><span>substr</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>返回子串<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-compare.html"><span class="t-lines"><span>compare</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>比较二个视图<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-starts_with.html"><span class="t-lines"><span>starts_with</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>检查 string_view 是否始于给定前缀<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-ends_with.html"><span class="t-lines"><span>ends_with</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>检查 string_view 是否终于给定后缀<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-contains.html"><span class="t-lines"><span>contains</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>检查字符串视图是否含有给定的子串或字符<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-find.html"><span class="t-lines"><span>find</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>在视图中查找字符<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-rfind.html"><span class="t-lines"><span>rfind</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>寻找子串的最后一次出现<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-find_first_of.html"><span class="t-lines"><span>find_first_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>查找字符的首次出现<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-find_last_of.html"><span class="t-lines"><span>find_last_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>查找字符的最后一次出现<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-find_first_not_of.html"><span class="t-lines"><span>find_first_not_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>查找字符的首次不出现<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-find_last_not_of.html"><span class="t-lines"><span>find_last_not_of</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>查找字符的最后一次不出现<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">
|
|
<h3><span class="mw-headline" id=".E5.B8.B8.E9.87.8F">常量</span></h3>
|
|
</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-npos.html"><span class="t-lines"><span>npos</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>特殊值。准确含义依赖于语境。<br />
|
|
<span class="t-mark">(公开静态成员常量)</span></td>
|
|
</tr>
|
|
</table>
|
|
<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>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-operator_cmp.html"><span class="t-lines"><span>operator==</span><span>operator!=</span><span>operator<</span><span>operator></span><span>operator<=</span><span>operator>=</span><span>operator<=></span></span></a></div>
|
|
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-until-cxx20">(C++20 中移除)</span></span><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>以字典序比较两个字符串视图<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">
|
|
<h5><span class="mw-headline" id=".E8.BE.93.E5.85.A5.2F.E8.BE.93.E5.87.BA">输入/输出</span></h5>
|
|
</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-operator_ltlt.html"><span class="t-lines"><span>operator<<</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>进行字符串视图的流输出<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.AD.97.E9.9D.A2.E9.87.8F">字面量</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc-header">
|
|
<td colspan="2">
|
|
<div>定义于内联命名空间 <code>std::literals::string_view_literals</code></div>
|
|
</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-operator_22_22sv.html"><span class="t-lines"><span>operator""sv</span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>创建一个字符数组字面量的字符串视图<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BE.85.E5.8A.A9.E7.B1.BB">辅助类</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-string-basic_string_view-hash.html"><span class="t-lines"><span>std::hash<span class="t-dsc-small"><std::string_view></span></span><span>std::hash<span class="t-dsc-small"><std::wstring_view></span></span><span>std::hash<span class="t-dsc-small"><std::u8string_view></span></span><span>std::hash<span class="t-dsc-small"><std::u16string_view></span></span><span>std::hash<span class="t-dsc-small"><std::u32string_view></span></span></span></a></div>
|
|
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>string_view 的散列支持<br />
|
|
<span class="t-mark">(类模板特化)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BE.85.E5.8A.A9.E6.A8.A1.E6.9D.BF">辅助模板</span></h3>
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dcl t-since-cxx20">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> CharT, <span class="kw1">class</span> Traits<span class="sy1">></span><br />
|
|
<span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> ranges<span class="sy4">::</span><span class="me2">enable_borrowed_range</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span> <span class="sy1">=</span> <span class="kw2">true</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p><a href="cpp-ranges-borrowed_range.html"><tt>std::ranges::enable_borrowed_range</tt></a> 的此特化使得 <code>basic_string_view</code> 满足 <a href="cpp-ranges-borrowed_range.html"><code>borrowed_range</code></a> 。</p>
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dcl t-since-cxx20">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> CharT, <span class="kw1">class</span> Traits<span class="sy1">></span><br />
|
|
<span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> ranges<span class="sy4">::</span><span class="me2">enable_view</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">basic_string_view</span><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span> <span class="sy1">=</span> <span class="kw2">true</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p><a href="cpp-ranges-view.html"><tt>std::ranges::enable_view</tt></a> 的此特化使得 <code>basic_string_view</code> 满足 <a href="cpp-ranges-view.html"><code>view</code></a> 。</p>
|
|
<h3><span class="mw-headline" id=".E6.8E.A8.E5.AF.BC.E6.8C.87.E5.BC.95.28C.2B.2B20_.E8.B5.B7.29"><a href="cpp-string-basic_string_view-deduction_guides.html">推导指引</a><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></h3>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p>程序员负责确保 <code>std::string_view</code> 不在被指向数组的生存期外继续生存：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1">std<span class="sy4">::</span><span class="me2">string_view</span> good<span class="br0">(</span><span class="st0">"a string literal"</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK ： "good" 指向静态数组</span>
|
|
std<span class="sy4">::</span><span class="me2">string_view</span> bad<span class="br0">(</span><span class="st0">"a temporary string"</span>s<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// "bad" 保有悬垂指针</span></pre></div>
|
|
</div>
|
|
<p>即使在 C++23 中引入的正式要求前，所有既存实现中 <code>std::basic_string_view</code> 的特化已经为可平凡复制类型。</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 <iostream></span>
|
|
<span class="co2">#include <string_view></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw4">constexpr</span> std<span class="sy4">::</span><span class="me2">string_view</span> unicode<span class="br0">[</span><span class="br0">]</span> <span class="br0">{</span>
|
|
<span class="st0">"▀▄─"</span>, <span class="st0">"▄▀─"</span>, <span class="st0">"▀─▄"</span>, <span class="st0">"▄─▀"</span>
|
|
<span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> y<span class="br0">{</span><span class="br0">}</span>, p<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> y <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">6</span><span class="sy4">;</span> <span class="sy2">++</span>y, p <span class="sy1">=</span> <span class="br0">(</span><span class="br0">(</span>p <span class="sy2">+</span> <span class="nu0">1</span><span class="br0">)</span> <span class="sy2">%</span> <span class="nu0">4</span><span class="br0">)</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> x<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> x <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">16</span><span class="sy4">;</span> <span class="sy2">++</span>x<span class="br0">)</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1753">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> unicode<span class="br0">[</span>p<span class="br0">]</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1753">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>可能的输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─
|
|
▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─
|
|
▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄▀─▄
|
|
▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀
|
|
▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─▀▄─
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