306 lines
15 KiB
HTML
306 lines
15 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::data</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_iterator_data 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>data</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-iterator.html">iterator</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-array.html"><array></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-deque.html"><deque></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-forward_list.html"><forward_list></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-iterator.html"><iterator></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-list.html"><list></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-map.html"><map></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-regex.html"><regex></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-set.html"><set></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-span.html"><span></a></code></div>
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</td>
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<td></td>
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<td>
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<div><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></div>
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</td>
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</tr>
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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.html"><string></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-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>
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<div><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></div>
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</td>
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</tr>
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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-unordered_map.html"><unordered_map></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-unordered_set.html"><unordered_set></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-dsc-header">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-vector.html"><vector></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><span class="kw1">class</span> C<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> data<span class="br0">(</span>C<span class="sy3">&</span> c<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>c.<span class="me1">data</span><span class="br0">(</span><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-cxx17">(C++17 起)</span></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><span class="kw1">class</span> C<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> data<span class="br0">(</span><span class="kw4">const</span> C<span class="sy3">&</span> c<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>c.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</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-cxx17">(C++17 起)</span></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><span class="kw1">class</span> T, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> T<span class="sy2">*</span> data<span class="br0">(</span>T <span class="br0">(</span><span class="sy3">&</span>array<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</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-cxx17">(C++17 起)</span></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><span class="kw1">class</span> E<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> <span class="kw4">const</span> E<span class="sy2">*</span> data<span class="br0">(</span><a href="cpp-utility-initializer_list.html"><span class="kw959">std::<span class="me2">initializer_list</span></span></a><span class="sy1"><</span>E<span class="sy1">></span> il<span class="br0">)</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-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>返回指向含有范围元素的内存块的指针。</p>
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<div class="t-li1"><span class="t-li">1,2)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">c.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span></span></span></div>
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<div class="t-li1"><span class="t-li">3)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">array</span></span></div>
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<div class="t-li1"><span class="t-li">4)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">il.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span></span></span></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>c</td>
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<td>-</td>
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<td>有 <span class="t-c"><span class="mw-geshi cpp source-cpp">data<span class="br0">(</span><span class="br0">)</span></span></span> 方法的容器或视图</td>
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</tr>
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<tr class="t-par">
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<td>array</td>
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<td>-</td>
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<td>任意类型的数组</td>
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</tr>
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<tr class="t-par">
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<td>il</td>
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<td>-</td>
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<td>initializer_list</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>指向含有容器范围的内存块的指针。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<div class="t-li1"><span class="t-li">1)</span> 可能抛出实现定义的异常。</div>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>需要对 <span class="t-lc"><a href="cpp-utility-initializer_list.html">std::initializer_list</a></span> 的重载，因为它无成员函数 <code>data</code> 。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<table class="eq-fun-cpp-table">
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<tr>
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<th>版本一</th>
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</tr>
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<tr>
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<td>
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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="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> C<span class="sy1">></span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> data<span class="br0">(</span>C<span class="sy3">&</span> c<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>c.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> c.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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</td>
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</tr>
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<tr>
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<th>版本二</th>
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</tr>
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<tr>
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<td>
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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="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> C<span class="sy1">></span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> data<span class="br0">(</span><span class="kw4">const</span> C<span class="sy3">&</span> c<span class="br0">)</span> <span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>c.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> c.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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</td>
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</tr>
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<tr>
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<th>版本三</th>
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</tr>
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<tr>
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<td>
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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="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> T, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">></span>
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<span class="kw4">constexpr</span> T<span class="sy2">*</span> data<span class="br0">(</span>T <span class="br0">(</span><span class="sy3">&</span>array<span class="br0">)</span><span class="br0">[</span>N<span class="br0">]</span><span class="br0">)</span> <span class="kw1">noexcept</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> array<span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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</td>
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</tr>
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<tr>
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<th>版本四</th>
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</tr>
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<tr>
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<td>
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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="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> E<span class="sy1">></span>
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<span class="kw4">constexpr</span> <span class="kw4">const</span> E<span class="sy2">*</span> data<span class="br0">(</span><a href="cpp-utility-initializer_list.html"><span class="kw959">std::<span class="me2">initializer_list</span></span></a><span class="sy1"><</span>E<span class="sy1">></span> il<span class="br0">)</span> <span class="kw1">noexcept</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> il.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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</td>
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</tr>
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</table>
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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 <string></span>
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<span class="co2">#include <cstring></span>
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<span class="co2">#include <iostream></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="kw1229">std::<span class="me2">string</span></span></a> s <span class="br0">{</span><span class="st0">"Hello world!<span class="es1">\n</span>"</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">char</span> a<span class="br0">[</span><span class="nu0">20</span><span class="br0">]</span><span class="sy4">;</span> <span class="co1">// C-style 风格字符串的存储</span>
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<a href="cpp-string-byte-strcpy.html"><span class="kw1139">std::<span class="me2">strcpy</span></span></a><span class="br0">(</span>a, std<span class="sy4">::</span><span class="me2">data</span><span class="br0">(</span>s<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// C++11 起 [s.data(), s.data() + s.size()] 保证为 NTBS</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> a<span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>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">Hello world!</pre></div>
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</div>
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</div>
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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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<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-ranges-data.html"><span class="t-lines"><span>ranges::data</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>
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<td>获得指向连续范围的起始的指针<br />
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<span class="t-mark">(定制点对象)</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-ranges-cdata.html"><span class="t-lines"><span>ranges::cdata</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>
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<td>获得指向只读连续范围的起始的指针<br />
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<span class="t-mark">(定制点对象)</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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</div>
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</div>
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</body>
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</html>
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