172 lines
13 KiB
HTML
172 lines
13 KiB
HTML
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<title>std::tuple_size<std:ranges::subrange></title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_ranges_subrange_tuple_size 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>tuple_size<small><std:ranges::subrange></small></h1>
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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-subrange.html">subrange</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-ranges.html"><ranges></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">class</span> I, <span class="kw1">class</span> S, ranges<span class="sy4">::</span><span class="me2">subrange_kind</span> K <span class="sy1">></span><br /></span>
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<p><span class="kw1">struct</span> tuple_size<span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">subrange</span><span class="sy1"><</span>I, S, K<span class="sy1">>></span><br /></p>
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<span class="sy4">:</span> <a href="cpp-types-integral_constant.html"><span class="kw647">std::<span class="me2">integral_constant</span></span></a><span class="sy1"><</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a>, <span class="nu0">2</span><span class="sy1">></span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p><a href="cpp-utility-tuple_size.html"><tt>std::tuple_size</tt></a> 对 <span class="t-lc">std::ranges::subrange</span> 的部分特化提供编译时获得 <code>subrange</code> 的组分数量的方式,该数始终为 2 。它是为结构化绑定支持提供的。</p>
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<div class="t-inherited">
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<h2><span class="mw-headline" id=".E7.BB.A7.E6.89.BF.E8.87.AA_std::integral_constant">继承自 <a href="cpp-types-integral_constant.html"><span style="font-size:0.7em; line-height:130%">std::</span>integral_constant</a></span></h2>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.B8.B8.E9.87.8F">成员常量</span></h3>
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<div><span class="t-lines"><span>value</span></span></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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<td>常量值 2<br />
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<span class="t-mark">(公开静态成员常量)</span></td>
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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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<div><span class="t-lines"><span>operator std::size_t</span></span></div>
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<td>转换对象为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a></span></span> ,返回 <code>value</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div><span class="t-lines"><span>operator()</span></span></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
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<td>返回 <code>value</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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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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<td>类型</td>
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<td>定义</td>
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<td><code>value_type</code></td>
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<td><code>std::size_t</code></td>
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<td><code>type</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-integral_constant.html"><span class="kw647">std::<span class="me2">integral_constant</span></span></a><span class="sy1"><</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a>, value<span class="sy1">></span></span></span></td>
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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 <array></span>
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<span class="co2">#include <iostream></span>
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<span class="co2">#include <iterator></span>
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<span class="co2">#include <ranges></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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static_assert<span class="br0">(</span><span class="nu0">2</span> <span class="sy1">==</span> <a href="cpp-utility-tuple-tuple_size.html"><span class="kw1102">std::<span class="me2">tuple_size_v</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">subrange</span><span class="sy1"><</span><span class="kw4">int</span><span class="sy2">*</span>, <span class="kw4">int</span><span class="sy2">*</span><span class="sy1">>></span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">using</span> array5 <span class="sy1">=</span> <a href="cpp-container-array.html"><span class="kw1268">std::<span class="me2">array</span></span></a><span class="sy1"><</span><span class="kw4">int</span>, <span class="nu0">5</span><span class="sy1">></span><span class="sy4">;</span>
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static_assert<span class="br0">(</span><span class="nu0">2</span> <span class="sy1">==</span> <a href="cpp-utility-tuple-tuple_size.html"><span class="kw1101">std::<span class="me2">tuple_size</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">subrange</span><span class="sy1"><</span>
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array5<span class="sy4">::</span><span class="me2">const_iterator</span>, array5<span class="sy4">::</span><span class="me2">const_iterator</span><span class="sy1">>></span><span class="br0">{</span><span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> array5 a<span class="br0">{</span> <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span> <span class="br0">}</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">subrange</span> sub_a1<span class="br0">{</span>a<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"sub_a1: { "</span><span class="sy4">;</span> <span class="kw4">int</span> e <span class="sy4">:</span> sub_a1<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> e <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span> <span class="br0">}</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">"}<span class="es1">\n</span>"</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">subrange</span> sub_a2<span class="br0">{</span><a href="cpp-iterator-next.html"><span class="kw674">std::<span class="me2">next</span></span></a><span class="br0">(</span>cbegin<span class="br0">(</span>a<span class="br0">)</span><span class="br0">)</span>, <a href="cpp-iterator-prev.html"><span class="kw675">std::<span class="me2">prev</span></span></a><span class="br0">(</span>cend<span class="br0">(</span>a<span class="br0">)</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> <span class="br0">[</span>first, last<span class="br0">]</span> <span class="sy1">=</span> sub_a2<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">"sub_a2 size = "</span> <span class="sy1"><<</span> <a href="cpp-iterator-distance.html"><span class="kw673">std::<span class="me2">distance</span></span></a><span class="br0">(</span>first, last<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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<span class="kw1">for</span> <span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"sub_a2: { "</span><span class="sy4">;</span> <span class="kw4">int</span> e <span class="sy4">:</span> sub_a2<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> e <span class="sy1"><<</span> <span class="st0">' '</span><span class="sy4">;</span> <span class="br0">}</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">"}<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></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">sub_a1: { 1 2 3 4 5 }
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sub_a2 size = 3
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sub_a2: { 2 3 4 }</pre></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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<td><a href="cpp-language-structured_binding.html">结构化绑定</a> <span class="t-mark-rev t-since-cxx17">(C++17)</span></td>
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<td>绑定指定的名字到初始化器的子对象或元组元素</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-utility-tuple_size.html"><span class="t-lines"><span>tuple_size</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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</div>
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</td>
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<td>获得元组式类型的元素数<br />
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<span class="t-mark">(类模板)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-ranges-subrange-tuple_element.html"><span class="t-lines"><span>std::tuple_element<span class="t-dsc-small"><std::ranges::subrange></span></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 <span class="t-lc">std::ranges::subrange</span> 的迭代器或哨位的类型<br />
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<span class="t-mark">(类模板特化)</span></td>
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</div>
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<div class="visualClear"></div>
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