227 lines
20 KiB
HTML
227 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::lexicographical_compare_three_way</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_algorithm_lexicographical_compare_three_way 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>lexicographical_compare_three_way</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-algorithm.html">algorithm</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-algorithm.html"><algorithm></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> <span class="kw1">class</span> InputIt1, <span class="kw1">class</span> InputIt2, <span class="kw1">class</span> Cmp <span class="sy1">></span><br /></span>
|
|
<p><span class="kw4">constexpr</span> <span class="kw4">auto</span> lexicographical_compare_three_way<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br />
|
|
InputIt2 first2, InputIt2 last2,<br />
|
|
Cmp comp<span class="br0">)</span><br /></p>
|
|
<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>comp<span class="br0">(</span><span class="sy2">*</span>first1, <span class="sy2">*</span>first2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</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> <span class="kw1">class</span> InputIt1, <span class="kw1">class</span> InputIt2 <span class="sy1">></span><br /></span>
|
|
<p><span class="kw4">constexpr</span> <span class="kw4">auto</span> lexicographical_compare_three_way<span class="br0">(</span> InputIt1 first1, InputIt1 last1,<br /></p>
|
|
InputIt2 first2, InputIt2 last2<span class="br0">)</span><span class="sy4">;</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-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>用三路比较，以字典序比较二个范围 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span>first1, last1<span class="br0">)</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span>first2, last2<span class="br0">)</span></span></span> ，并产生最强可应用比较类别类型的结果。</p>
|
|
<div class="t-li1"><span class="t-li">1)</span> 返回两个范围中首对按照 <code>comp</code> 不等价的元素间的序，若它们存在，否则（若一个范围按照 <code>comp</code> 等价于另一个范围的前缀）返回两个范围长度间的序。</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 等价于：
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">lexicographical_compare_three_way</span><span class="br0">(</span>
|
|
first1, last1, first2, last2, std<span class="sy4">::</span><span class="me2">compare_three_way</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>first1, last1</td>
|
|
<td>-</td>
|
|
<td>要检验的第一元素范围</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>first2, last2</td>
|
|
<td>-</td>
|
|
<td>要检验的第二元素范围</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>comp</td>
|
|
<td>-</td>
|
|
<td>函数对象类型。若其返回类型不是三个比较类别类型（ <a href="cpp-utility-compare-strong_ordering.html"><tt>std::strong_ordering</tt></a>、 <a href="cpp-utility-compare-weak_ordering.html"><tt>std::weak_ordering</tt></a> 或 <a href="cpp-utility-compare-partial_ordering.html"><tt>std::partial_ordering</tt></a> ）之一则程序非良构。</td>
|
|
</tr>
|
|
<tr class="t-par-hitem">
|
|
<td colspan="3">类型要求</td>
|
|
</tr>
|
|
<tr class="t-par-req">
|
|
<td colspan="3">-
|
|
<div class="spacer"></div>
|
|
<code>InputIt1, InputIt2</code> 必须满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> 的要求。</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p>定义如上的比较类别类型的值。</p>
|
|
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
|
|
<p>至多应用 <i>N</i> 次 <code>comp</code> ，其中 <i>N</i> 为两范围长度的较小者。</p>
|
|
<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>
|
|
<table class="eq-fun-cpp-table">
|
|
<tr>
|
|
<td>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> I1, <span class="kw1">class</span> I2, <span class="kw1">class</span> Cmp <span class="sy1">></span>
|
|
<span class="kw4">constexpr</span> <span class="kw4">auto</span> lexicographical_compare_three_way<span class="br0">(</span> I1 f1, I1 l1, I2 f2, I2 l2, Cmp comp <span class="br0">)</span>
|
|
<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>comp<span class="br0">(</span><span class="sy2">*</span>f1, <span class="sy2">*</span>f2<span class="br0">)</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<span class="kw1">using</span> ret_t <span class="sy1">=</span> decltype<span class="br0">(</span>comp<span class="br0">(</span><span class="sy2">*</span>f1, <span class="sy2">*</span>f2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
|
|
static_assert<span class="br0">(</span><a href="cpp-types-disjunction.html"><span class="kw644">std::<span class="me2">disjunction_v</span></span></a><span class="sy1"><</span>
|
|
<a href="cpp-types-is_same.html"><span class="kw588">std::<span class="me2">is_same</span></span></a><span class="sy1"><</span>ret_t, std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy1">></span>,
|
|
<a href="cpp-types-is_same.html"><span class="kw588">std::<span class="me2">is_same</span></span></a><span class="sy1"><</span>ret_t, std<span class="sy4">::</span><span class="me2">weak_ordering</span><span class="sy1">></span>,
|
|
<a href="cpp-types-is_same.html"><span class="kw588">std::<span class="me2">is_same</span></span></a><span class="sy1"><</span>ret_t, std<span class="sy4">::</span><span class="me2">partial_ordering</span><span class="sy1">>></span>,
|
|
<span class="st0">"The return type must be a comparison category type."</span><span class="br0">)</span><span class="sy4">;</span>
|
|
|
|
<span class="kw4">bool</span> exhaust1 <span class="sy1">=</span> <span class="br0">(</span>f1 <span class="sy1">==</span> l1<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw4">bool</span> exhaust2 <span class="sy1">=</span> <span class="br0">(</span>f2 <span class="sy1">==</span> l2<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;</span> <span class="sy3">!</span>exhaust1 <span class="sy3">&&</span> <span class="sy3">!</span>exhaust2<span class="sy4">;</span> exhaust1 <span class="sy1">=</span> <span class="br0">(</span><span class="sy2">++</span>f1 <span class="sy1">==</span> l1<span class="br0">)</span>, exhaust2 <span class="sy1">=</span> <span class="br0">(</span><span class="sy2">++</span>f2 <span class="sy1">==</span> l2<span class="br0">)</span><span class="br0">)</span>
|
|
<span class="kw1">if</span> <span class="br0">(</span><span class="kw4">auto</span> c <span class="sy1">=</span> comp<span class="br0">(</span><span class="sy2">*</span>f1, <span class="sy2">*</span>f2<span class="br0">)</span><span class="sy4">;</span> c <span class="sy3">!</span><span class="sy1">=</span> <span class="nu0">0</span><span class="br0">)</span>
|
|
<span class="kw1">return</span> c<span class="sy4">;</span>
|
|
|
|
<span class="kw1">return</span> <span class="sy3">!</span>exhaust1 <span class="sy4">?</span> std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy4">::</span><span class="me2">greater</span> <span class="sy4">:</span>
|
|
<span class="sy3">!</span>exhaust2 <span class="sy4">?</span> std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy4">::</span><span class="me2">less</span> <span class="sy4">:</span>
|
|
std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy4">::</span><span class="me2">equal</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
</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 <cctype></span>
|
|
<span class="co2">#include <compare></span>
|
|
<span class="co2">#include <iomanip></span>
|
|
<span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <string_view></span>
|
|
<span class="co2">#include <utility></span>
|
|
<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">;</span>
|
|
|
|
<span class="kw4">void</span> show_result<span class="br0">(</span><a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a> s1, <a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a> s2, std<span class="sy4">::</span><span class="me2">strong_ordering</span> o<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> quoted<span class="br0">(</span>s1<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">" is "</span><span class="sy4">;</span>
|
|
<span class="br0">(</span>o <span class="sy1"><</span> <span class="nu0">0</span><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> <span class="st0">"less than "</span> <span class="sy4">:</span>
|
|
<span class="br0">(</span>o <span class="sy1">></span> <span class="nu0">0</span><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> <span class="st0">"greater than "</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> <span class="st0">"equal to "</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> quoted<span class="br0">(</span>s2<span class="br0">)</span> <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">auto</span> cmp_icase <span class="sy1">=</span> <span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">char</span> x, <span class="kw4">char</span> y<span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw4">const</span> <span class="kw4">auto</span> ux <span class="br0">{</span> std<span class="sy4">::</span><span class="me2">toupper</span><span class="br0">(</span>x<span class="br0">)</span> <span class="br0">}</span><span class="sy4">;</span>
|
|
<span class="kw4">const</span> <span class="kw4">auto</span> uy <span class="br0">{</span> std<span class="sy4">::</span><span class="me2">toupper</span><span class="br0">(</span>y<span class="br0">)</span> <span class="br0">}</span><span class="sy4">;</span>
|
|
<span class="kw1">return</span> <span class="br0">(</span>ux <span class="sy1"><</span> uy<span class="br0">)</span> <span class="sy4">?</span> std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy4">::</span><span class="me2">less</span><span class="sy4">:</span>
|
|
<span class="br0">(</span>ux <span class="sy1">></span> uy<span class="br0">)</span> <span class="sy4">?</span> std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy4">::</span><span class="me2">greater</span><span class="sy4">:</span>
|
|
std<span class="sy4">::</span><span class="me2">strong_ordering</span><span class="sy4">::</span><span class="me2">equal</span><span class="sy4">;</span>
|
|
<span class="br0">}</span><span class="sy4">;</span>
|
|
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">const</span> <span class="kw4">auto</span><span class="sy3">&</span> <span class="br0">[</span>s1, s2<span class="br0">]</span> <span class="sy4">:</span> <span class="br0">{</span> <a href="cpp-utility-pair.html"><span class="kw1096">std::<span class="me2">pair</span></span></a><span class="br0">{</span><span class="st0">"one"</span>sv, <span class="st0">"ONE"</span>sv<span class="br0">}</span>,
|
|
<span class="br0">{</span><span class="st0">"two"</span>sv, <span class="st0">"four"</span>sv<span class="br0">}</span>,
|
|
<span class="br0">{</span><span class="st0">"three"</span>sv, <span class="st0">"two"</span>sv<span class="br0">}</span> <span class="br0">}</span><span class="br0">)</span> <span class="br0">{</span>
|
|
<span class="kw4">const</span> <span class="kw4">auto</span> res <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">lexicographical_compare_three_way</span><span class="br0">(</span>
|
|
s1.<span class="me1">cbegin</span><span class="br0">(</span><span class="br0">)</span>, s1.<span class="me1">cend</span><span class="br0">(</span><span class="br0">)</span>, s2.<span class="me1">cbegin</span><span class="br0">(</span><span class="br0">)</span>, s2.<span class="me1">cend</span><span class="br0">(</span><span class="br0">)</span>, cmp_icase<span class="br0">)</span><span class="sy4">;</span>
|
|
show_result<span class="br0">(</span>s1, s2, res<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</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">"one" is equal to "ONE"
|
|
"two" is greater than "four"
|
|
"three" is less than "two"</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://cplusplus.github.io/LWG/issue3410">LWG 3410</a></td>
|
|
<td>C++20</td>
|
|
<td>要求了额外的迭代器间比较</td>
|
|
<td>移除该要求</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-algorithm-lexicographical_compare.html"><span class="t-lines"><span>lexicographical_compare</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>当一个范围按字典顺序小于另一个范围时，返回 true<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-utility-compare-compare_three_way.html"><span class="t-lines"><span>compare_three_way</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>实现 <span class="t-c"><span class="mw-geshi cpp source-cpp">x <span class="sy1"><=></span> y</span></span> 的函数对象<br />
|
|
<span class="t-mark">(类)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-algorithm-ranges-lexicographical_compare.html"><span class="t-lines"><span>ranges::lexicographical_compare</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>当一个范围按字典顺序小于另一个范围时，返回 true<br />
|
|
<span class="t-mark">(niebloid)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|