147 lines
14 KiB
HTML
147 lines
14 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::iter_value_t, std::iter_reference_t, std::iter_difference_t, std::iter_rvalue_reference_t, std::iter_common_reference_t</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_iterator_iter_t skin-cppreference2 action-view cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>iter_value_t, <span style="font-size:0.7em; line-height:130%">std::</span>iter_reference_t, <span style="font-size:0.7em; line-height:130%">std::</span>iter_difference_t, <span style="font-size:0.7em; line-height:130%">std::</span>iter_rvalue_reference_t, <span style="font-size:0.7em; line-height:130%">std::</span>iter_common_reference_t</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-iterator.html">iterator</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dsc-header">
|
|
<td>
|
|
<div>定义于头文件 <code><a href="cpp-header-iterator.html"><iterator></a></code></div>
|
|
</td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
<tr class="t-dcl">
|
|
<td class="t-dcl-nopad">
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> T <span class="sy1">></span><br />
|
|
concept __Referenceable <span class="sy1">=</span> <span class="coMULTI">/* see below */</span><span class="sy4">;</span> <span class="co1">// 仅用于阐释</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td class="t-dcl-nopad"></td>
|
|
</tr>
|
|
<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> T <span class="sy1">></span><br />
|
|
<span class="kw1">using</span> iter_value_t <span class="sy1">=</span> <span class="coMULTI">/* see below */</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(1)</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<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> __Referenceable T <span class="sy1">></span><br />
|
|
<span class="kw1">using</span> iter_reference_t <span class="sy1">=</span> decltype<span class="br0">(</span><span class="sy2">*</span><a href="cpp-utility-declval.html"><span class="kw1120">std::<span class="me2">declval</span></span></a><span class="sy1"><</span>T<span class="sy3">&</span><span class="sy1">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(2)</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<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> T <span class="sy1">></span><br />
|
|
<span class="kw1">using</span> iter_difference_t <span class="sy1">=</span> <span class="coMULTI">/* see below */</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td>(3)</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<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> __Referenceable T<span class="sy1">></span><br /></span>
|
|
<p> requires <span class="coMULTI">/* see below */</span><br /></p>
|
|
<span class="kw1">using</span> iter_rvalue_reference_t <span class="sy1">=</span> decltype<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">iter_move</span><span class="br0">(</span><a href="cpp-utility-declval.html"><span class="kw1120">std::<span class="me2">declval</span></span></a><span class="sy1"><</span>T<span class="sy3">&</span><span class="sy1">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></div>
|
|
</td>
|
|
<td>(4)</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<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> std<span class="sy4">::</span><span class="me2">indirectly_readable</span> T <span class="sy1">></span><br /></span>
|
|
<p><span class="kw1">using</span> iter_common_reference_t <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">common_reference_t</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">iter_reference_t</span><span class="sy1"><</span>T<span class="sy1">></span>,<br /></p>
|
|
std<span class="sy4">::</span><span class="me2">iter_value_t</span><span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span><span class="sy1">></span><span class="sy4">;</span></div>
|
|
</td>
|
|
<td>(5)</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>计算迭代器的关联类型。仅用于阐释的概念 <code><i>__Referenceable</i></code> 若且唯若表达式 <code>*std::declval<T&>()</code> 合法且拥有可引用类型（特别是非 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> ）才得到满足。</p>
|
|
<div class="t-li1"><span class="t-li">1)</span> 计算 <code>T</code> 的<i>值类型</i>。若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_traits.html"><span class="kw651">std::<span class="me2">iterator_traits</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>T<span class="sy1">>></span></span></span> 未被特化，则 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">iter_value_t</span><span class="sy1"><</span>T<span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">indirectly_readable_traits</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>T<span class="sy1">>></span><span class="sy4">::</span><span class="me2">value_type</span></span></span> 。否则它是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_traits.html"><span class="kw651">std::<span class="me2">iterator_traits</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>T<span class="sy1">>></span><span class="sy4">::</span><span class="me2">value_type</span></span></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 计算 <code>T</code> 的<i>引用类型</i>。</div>
|
|
<div class="t-li1"><span class="t-li">3)</span> 计算 <code>T</code> 的<i>差类型</i>。若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_traits.html"><span class="kw651">std::<span class="me2">iterator_traits</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>T<span class="sy1">>></span></span></span> 未被特化，则 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">iter_difference_t</span><span class="sy1"><</span>T<span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">incrementable_traits</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>T<span class="sy1">>></span><span class="sy4">::</span><span class="me2">difference_type</span></span></span> 。否则它是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-iterator-iterator_traits.html"><span class="kw651">std::<span class="me2">iterator_traits</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">remove_cvref_t</span><span class="sy1"><</span>T<span class="sy1">>></span><span class="sy4">::</span><span class="me2">difference_type</span></span></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">4)</span> 计算 <code>T</code> 的<i>右值引用类型</i>。此别名模版上的制约的 "see below" 部分若且唯若表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">iter_move</span><span class="br0">(</span><a href="cpp-utility-declval.html"><span class="kw1120">std::<span class="me2">declval</span></span></a><span class="sy1"><</span>T<span class="sy3">&</span><span class="sy1">></span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span></span></span> 合法且拥有可引用类型（特别是非 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> ）才得到满足。</div>
|
|
<div class="t-li1"><span class="t-li">5)</span> 计算 <code>T</code> 的<i>共用引用类型</i>。此乃其引用类型与到其值类型的左值引用类型的共用引用类型。</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-indirectly_readable.html"><span class="t-lines"><span>indirectly_readable</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>指定类型通过应用运算符 <code>*</code> 可读<br />
|
|
<span class="t-mark">(概念)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-weakly_incrementable.html"><span class="t-lines"><span>weakly_incrementable</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>指定 <a href="cpp-concepts-semiregular.html"><code>semiregular</code></a> 类型能以前后自增运算符自增<br />
|
|
<span class="t-mark">(概念)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-indirectly_readable_traits.html"><span class="t-lines"><span>indirectly_readable_traits</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>计算 <a href="cpp-iterator-indirectly_readable.html"><code>indirectly_readable</code></a> 类型的值类型<br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-incrementable_traits.html"><span class="t-lines"><span>incrementable_traits</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>计算 <a href="cpp-iterator-weakly_incrementable.html"><code>weakly_incrementable</code></a> 类型的差类型<br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-iterator_traits.html"><span class="t-lines"><span>iterator_traits</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>为迭代器各项性质提供统一接口<br />
|
|
<span class="t-mark">(类模板)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|