62 lines
6.0 KiB
HTML
62 lines
6.0 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::experimental::ranges::ForwardIterator</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_experimental_ranges_iterator_ForwardIterator 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::experimental::ranges::</span>ForwardIterator</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-experimental.html">experimental</a>‎ | <a href="cpp-experimental-ranges.html">ranges</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-experimental-ranges-iterator.html"><experimental/ranges/iterator></a></code></div>
|
|
</td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-ranges">
|
|
<td>
|
|
<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="sy1">></span><br /></span>
|
|
<p>concept <span class="kw4">bool</span> ForwardIterator <span class="sy1">=</span><br />
|
|
<a href="cpp-experimental-ranges-iterator-InputIterator.html"><span class="kw2569">ranges::<span class="me2">InputIterator</span></span></a><span class="sy1"><</span>I<span class="sy1">></span> <span class="sy3">&&</span><br />
|
|
<a href="cpp-experimental-ranges-concepts-DerivedFrom.html"><span class="kw2531">ranges::<span class="me2">DerivedFrom</span></span></a><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_category_t</span><span class="sy1"><</span>I<span class="sy1">></span>, ranges<span class="sy4">::</span><span class="me2">forward_iterator_tag</span><span class="sy1">></span> <span class="sy3">&&</span><br />
|
|
<a href="cpp-experimental-ranges-iterator-Incrementable.html"><span class="kw2565">ranges::<span class="me2">Incrementable</span></span></a><span class="sy1"><</span>I<span class="sy1">></span> <span class="sy3">&&</span><br /></p>
|
|
<a href="cpp-experimental-ranges-iterator-Sentinel.html"><span class="kw2567">ranges::<span class="me2">Sentinel</span></span></a><span class="sy1"><</span>I, I<span class="sy1">></span><span class="sy4">;</span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-ranges-ts t-mark-ts">(范围 TS)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>概念 <code>ForwardIterator<I></code> 细化 <a href="cpp-experimental-ranges-iterator-InputIterator.html"><code>InputIterator</code></a> ，添加相等比较和多趟保证。</p>
|
|
<p><code>==</code> 对于向前迭代器的定义域是同一底层序列上的迭代器的定义域，除了值初始化的同类型迭代器可能彼此比较，并应当比较相等。</p>
|
|
<p>在 <code>[i, s)</code> 一直代表范围时，从指向范围 <code>[i, s)</code> 中的向前迭代器获得的指针和引用必须保持合法。</p>
|
|
<p>令 <code>a</code> 与 <code>b</code> 为二个 <code>I</code> 类型的可解引用迭代器。 <code>ForwardIterator<I></code> 仅若符合下列条件才得到满足：</p>
|
|
<ul>
|
|
<li><span class="t-c"><span class="mw-geshi cpp source-cpp">a <span class="sy1">==</span> b</span></span> 隐含 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">++</span>a <span class="sy1">==</span> <span class="sy2">++</span>b</span></span> ；且</li>
|
|
<li>表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span><span class="br0">[</span><span class="br0">]</span><span class="br0">(</span>X x<span class="br0">)</span><span class="br0">{</span><span class="sy2">++</span>x<span class="sy4">;</span><span class="br0">}</span><span class="br0">(</span>a<span class="br0">)</span>, <span class="sy2">*</span>a<span class="br0">)</span></span></span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>a</span></span> ，即自增 <code>a</code> 的副本在解引用 <code>a</code></li>
|
|
</ul>
|
|
<p>这被称为<i>多趟保证</i>。</p>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
|
|
<p>向前迭代器不能“贮藏”：它不能返回到其自身内对象的引用，因为向前迭代器的析构会非法化这种引用。</p>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|