339 lines
20 KiB
HTML
339 lines
20 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::counted_iterator</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_counted_iterator 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>counted_iterator</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 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">input_or_output_iterator</span> I <span class="sy1">></span><br />
|
|
<span class="kw1">class</span> counted_iterator<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><code>std::counted_iterator</code> 是表现准确同底层迭代器的迭代器适配器，除了它记录到其范围末尾的距离。此迭代器等于 <span class="t-lc">std::default_sentinel</span> 当且仅当其计数抵达零。</p>
|
|
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc-hitem">
|
|
<td>成员类型</td>
|
|
<td>定义</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code>iterator_type</code></td>
|
|
<td><code>I</code></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code>value_type</code></td>
|
|
<td>若 <code>I</code> 实现 <a href="cpp-iterator-indirectly_readable.html"><code>indirectly_readable</code></a> 则为 <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>I<span class="sy1">></span></span></span> ；否则不定义</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code>difference_type</code></td>
|
|
<td><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>I<span class="sy1">></span></span></span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code>iterator_concept</code></td>
|
|
<td>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">I<span class="sy4">::</span><span class="me2">iterator_concept</span></span></span> 存在则为它；否则不定义</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code>iterator_category</code></td>
|
|
<td>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">I<span class="sy4">::</span><span class="me2">iterator_category</span></span></span> 存在则为它；否则不定义</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div t-dsc-member-nobold-div">
|
|
<div><a href="cpp-iterator-counted_iterator-counted_iterator.html"><span class="t-lines"><span>(构造函数)</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>构造新的迭代器适配器<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-iterator-counted_iterator-operator=.html"><span class="t-lines"><span>operator=</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>赋值另一迭代器适配器<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-iterator-counted_iterator-base.html"><span class="t-lines"><span>base</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>访问底层迭代器<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-iterator-counted_iterator-count.html"><span class="t-lines"><span>count</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>返回到末尾的距离<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-iterator-counted_iterator-operator*.html"><span class="t-lines"><span>operator*</span><span>operator-></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>访问被指向的元素<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-iterator-counted_iterator-operator_at.html"><span class="t-lines"><span>operator[]</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>按索引访问元素<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-iterator-counted_iterator-operator_arith.html"><span class="t-lines"><span>operator++</span><span>operator++<span class="t-dsc-small">(int)</span></span><span>operator+=</span><span>operator+</span><span>operator--</span><span>operator--<span class="t-dsc-small">(int)</span></span><span>operator-=</span><span>operator-</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>推进或回退迭代器<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.AF.B9.E8.B1.A1">成员对象</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc-hitem">
|
|
<td>成员名</td>
|
|
<td>定义</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code><i>current</i></code> <span class="t-mark">(私有)</span></td>
|
|
<td><a href="cpp-iterator-counted_iterator-base.html"><code>base()</code></a> 所访问的底层迭代器，名字仅用于阐释</td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td><code><i>length</i></code> <span class="t-mark">(私有)</span></td>
|
|
<td>底层迭代器与其范围末尾的距离，名字仅用于阐释</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-iterator-counted_iterator-operator_cmp.html"><span class="t-lines"><span>operator==</span><span>operator<=></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>比较到末尾的距离<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-counted_iterator-operator_cmp2.html"><span class="t-lines"><span>operator==<span class="t-dsc-small">(std::default_sentinel)</span></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>检查到末尾的距离是否等于 <code>​0​</code><br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-counted_iterator-operator+.html"><span class="t-lines"><span>operator+</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>令迭代器前进<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-counted_iterator-operator-.html"><span class="t-lines"><span>operator-</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>计算两个迭代器适配器间的距离<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-counted_iterator-operator-2.html"><span class="t-lines"><span>operator-<span class="t-dsc-small">(std::default_sentinel_t)</span></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>计算到末尾的有符号距离<br />
|
|
<span class="t-mark">(函数模板)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-counted_iterator-iter_move.html"><span class="t-lines"><span>iter_move</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>转型解引用底层迭代器的结果为其所关联的右值引用类型<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-iterator-counted_iterator-iter_swap.html"><span class="t-lines"><span>iter_swap</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>交换二个底层迭代器所指向的对象<br />
|
|
<span class="t-mark">(函数模板)</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-iterator-counted_iterator-iterator_traits.html"><span class="t-lines"><span>std::iterator_traits<span class="t-dsc-small"><std::counted_iterator></span></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>对 <span class="t-lc">std::counted_iterator</span> 类型的属性提供均一的接口<br />
|
|
<span class="t-mark">(类模板特化)</span></td>
|
|
</tr>
|
|
</table>
|
|
<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 <algorithm></span>
|
|
<span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <iterator></span>
|
|
<span class="co2">#include <string></span>
|
|
<span class="co2">#include <vector></span>
|
|
<span class="kw1">using</span> std<span class="sy4">::</span><span class="me2">operator</span><span class="st0">""</span>s<span class="sy4">;</span>
|
|
|
|
<span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">auto</span> <span class="kw4">const</span> remark, <span class="kw4">auto</span> <span class="kw4">const</span><span class="sy3">&</span> v<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw4">const</span> <span class="kw4">auto</span> size <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ssize</span><span class="br0">(</span>v<span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> remark <span class="sy1"><<</span> <span class="st0">"["</span> <span class="sy1"><<</span> size <span class="sy1"><<</span> <span class="st0">"] { "</span><span class="sy4">;</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">auto</span> it <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">counted_iterator</span><span class="br0">{</span><a href="cpp-iterator-begin.html"><span class="kw677">std::<span class="me2">cbegin</span></span></a><span class="br0">(</span>v<span class="br0">)</span>, size<span class="br0">}</span><span class="sy4">;</span>
|
|
it <span class="sy3">!</span><span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">default_sentinel</span><span class="sy4">;</span> <span class="sy2">++</span>it<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> <span class="sy2">*</span>it <span class="sy1"><<</span> <span class="st0">", "</span><span class="sy4">;</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">"}<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw4">const</span> <span class="kw4">auto</span> src <span class="sy1">=</span> <span class="br0">{</span><span class="st0">"Arcturus"</span>s, <span class="st0">"Betelgeuse"</span>s, <span class="st0">"Canopus"</span>s, <span class="st0">"Deneb"</span>s, <span class="st0">"Elnath"</span>s <span class="br0">}</span><span class="sy4">;</span>
|
|
print<span class="br0">(</span><span class="st0">"src"</span>, src<span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span>decltype<span class="br0">(</span>src<span class="br0">)</span><span class="sy4">::</span><span class="me2">value_type</span><span class="sy1">></span> dst<span class="sy4">;</span>
|
|
std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">copy</span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">counted_iterator</span><span class="br0">{</span>src.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">3</span><span class="br0">}</span>,
|
|
std<span class="sy4">::</span><span class="me2">default_sentinel</span>,
|
|
<a href="cpp-iterator-back_inserter.html"><span class="kw665">std::<span class="me2">back_inserter</span></span></a><span class="br0">(</span>dst<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
|
|
print<span class="br0">(</span><span class="st0">"dst"</span>, dst<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">src[5] { Arcturus, Betelgeuse, Canopus, Deneb, Elnath, }
|
|
dst[3] { Arcturus, Betelgeuse, Canopus, }</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
|
|
<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
|
|
<table class="dsctable" style="font-size:0.8em">
|
|
<tr>
|
|
<th>DR</th>
|
|
<th>应用于</th>
|
|
<th>出版时的行为</th>
|
|
<th>正确行为</th>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://wg21.link/P2259R1">P2259R1</a></td>
|
|
<td>C++20</td>
|
|
<td>不提供成员 typedef<br />
|
|
对 <code>counted_iterator</code> 特化 <span class="t-lc">std::incrementable_traits</span></td>
|
|
<td>添加成员 typedef 以顾及 <a href="cpp-iterator-counted_iterator-iterator_traits.html"><tt>iterator_traits</tt></a> 修正<br />
|
|
移除了冗余的 <span class="t-lc">std::incrementable_traits</span> 特化</td>
|
|
</tr>
|
|
</table>
|
|
<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-default_sentinel_t.html"><span class="t-lines"><span>default_sentinel_t</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>用于知晓其边界的迭代器的默认哨位<br />
|
|
<span class="t-mark">(类)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-ranges-view_counted.html"><span class="t-lines"><span>views::counted</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>从迭代器和计数创建子范围<br />
|
|
<span class="t-mark">(定制点对象)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-ranges-take_view.html"><span class="t-lines"><span>ranges::take_view</span><span>views::take</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>由另一 <a href="cpp-ranges-view.html"><code>view</code></a> 的前 N 个元素组成的 <a href="cpp-ranges-view.html"><code>view</code></a><br />
|
|
<span class="t-mark">(类模板)</span> <span class="t-mark">(范围适配器对象)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|