89 lines
5.9 KiB
HTML
89 lines
5.9 KiB
HTML
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<title>std::hash (std::string_view, std::wstring_view, std::u16string_view, std::u32string_view)</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_basic_string_view_hash 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::</span>hash <small>(std::string_view, std::wstring_view, std::u16string_view, std::u32string_view)</small></h1>
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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>定义于头文件 <code><a href="cpp-header-string_view.html"><string_view></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span> <span class="kw1">struct</span> hash<span class="sy1"><</span><a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></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">struct</span> hash<span class="sy1"><</span><a href="cpp-string-basic_string_view.html"><span class="kw1250">std::<span class="me2">wstring_view</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></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">struct</span> hash<span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">u8string_view</span><span class="sy1">></span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span> <span class="kw1">struct</span> hash<span class="sy1"><</span><a href="cpp-string-basic_string_view.html"><span class="kw1252">std::<span class="me2">u16string_view</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></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">struct</span> hash<span class="sy1"><</span><a href="cpp-string-basic_string_view.html"><span class="kw1254">std::<span class="me2">u32string_view</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<p><span class="t-lc"><a href="cpp-utility-hash.html">std::hash</a></span> 对各种视图类的模板特化，目的是对视图哈希。</p>
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<p>这些哈希等于对应的 <span class="t-lc"><a href="cpp-string-basic_string.html">std::basic_string</a></span> 类的哈希：若 <code>S</code> 是标准 <code>basic_string</code> 类型，而 <code>SV</code> 是对应的 string_view 类型，且 <code>s</code> 是 <code>S</code> 类型对象，则 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-hash.html"><span class="kw1124">std::<span class="me2">hash</span></span></a><span class="sy1"><</span>S<span class="sy1">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>s<span class="br0">)</span> <span class="sy1">==</span> <a href="cpp-utility-hash.html"><span class="kw1124">std::<span class="me2">hash</span></span></a><span class="sy1"><</span>SV<span class="sy1">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>SV<span class="br0">(</span>s<span class="br0">)</span><span class="br0">)</span></span></span> 。</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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<div><a href="cpp-utility-hash.html"><span class="t-lines"><span>hash</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>散列函数对象<br />
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<span class="t-mark">(类模板)</span></td>
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