338 lines
34 KiB
HTML
338 lines
34 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>std::ranges::search</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_algorithm_ranges_search skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::ranges::</span>search</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-algorithm.html">algorithm</a>‎ | <a href="cpp-algorithm-ranges.html">ranges</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<div>定义于头文件 <code><a href="cpp-header-algorithm.html"><algorithm></a></code></div>
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<td></td>
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<div>调用签名</div>
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<td></td>
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<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">forward_iterator</span> I1, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I1<span class="sy1">></span> S1,<br /></span>
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<p> std<span class="sy4">::</span><span class="me2">forward_iterator</span> I2, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I2<span class="sy1">></span> S2,<br />
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<span class="kw1">class</span> Pred <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">equal_to</span>,<br />
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<span class="kw1">class</span> Proj1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,<br />
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<span class="kw1">class</span> Proj2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span> <span class="sy1">></span><br />
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requires std<span class="sy4">::</span><span class="me2">indirectly_comparable</span><span class="sy1"><</span>I1, I2, Pred, Proj1, Proj2<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">subrange</span><span class="sy1"><</span>I1<span class="sy1">></span><br />
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search<span class="br0">(</span> I1 first1, S1 last1, I2 first2, S2 last2, Pred pred <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>,<br /></p>
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Proj1 proj1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj2 proj2 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span> <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> ranges<span class="sy4">::</span><span class="me2">forward_range</span> R1, ranges<span class="sy4">::</span><span class="me2">forward_range</span> R2,<br /></span>
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<p> <span class="kw1">class</span> Pred <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">equal_to</span>,<br />
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<span class="kw1">class</span> Proj1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,<br />
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<span class="kw1">class</span> Proj2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span><span class="sy1">></span><br />
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requires std<span class="sy4">::</span><span class="me2">indirectly_comparable</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R1<span class="sy1">></span>,<br />
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ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R2<span class="sy1">></span>, Pred, Proj1, Proj2<span class="sy1">></span><br />
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">borrowed_subrange_t</span><span class="sy1"><</span>R1<span class="sy1">></span><br /></p>
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search<span class="br0">(</span> R1<span class="sy3">&&</span> r1, R2<span class="sy3">&&</span> r2, Pred pred <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj1 proj1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj2 proj2 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span> <span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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<div class="t-li1"><span class="t-li">1)</span> 在范围 <code>[first1, last1)</code> 中搜索元素序列 <code>[first2, last2)</code> 的<i>首次</i>出现。在分别用 <code>proj1</code> 与 <code>proj2</code> 投影后用二元谓词 <code>pred</code> 比较元素。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，但以 <code>r1</code> 为第一范围并以 <code>r2</code> 为第二范围，如同以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r1<span class="br0">)</span></span></span> 为 <code>first1</code> ，以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r1<span class="br0">)</span></span></span> 为 <code>last1</code> ，以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r2<span class="br0">)</span></span></span> 为 <code>first2</code> ，并以 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r2<span class="br0">)</span></span></span> 为 <code>last2</code> 。</div>
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<p>此页面上描述的仿函数实体是 <i>niebloid</i> ，即：</p>
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<ul>
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<li>调用它们中的任何一者时不可指定显式模板实参。</li>
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<li>它们无一对<a href="cpp-language-adl.html">实参依赖查找</a>可见。</li>
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<li>在<a href="cpp-language-unqualified_lookup.html">通常无限定查找</a>寻找函数调用运算符左侧的名称找到它们之一时，它禁止<a href="cpp-language-adl.html">实参依赖查找</a>。</li>
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</ul>
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<p>实际上，它们能以函数对象，或以某些特殊编译器扩展实现。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>first1, last1</td>
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<td>-</td>
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<td>要检验的元素范围（又称<i>草堆</i>）</td>
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</tr>
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<tr class="t-par">
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<td>first2, last2</td>
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<td>-</td>
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<td>要搜索的元素范围（又称<i>针</i>）</td>
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</tr>
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<tr class="t-par">
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<td>r1</td>
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<td>-</td>
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<td>要检验的元素范围（又称<i>草堆</i>）</td>
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</tr>
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<tr class="t-par">
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<td>r2</td>
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<td>-</td>
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<td>要搜索的元素范围（又称<i>针</i>）</td>
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</tr>
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<tr class="t-par">
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<td>pred</td>
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<td>-</td>
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<td>应用到投影后元素的谓词</td>
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</tr>
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<tr class="t-par">
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<td>proj1</td>
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<td>-</td>
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<td>应用到第一范围中元素的投影</td>
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</tr>
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<tr class="t-par">
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<td>proj2</td>
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<td>-</td>
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<td>应用到第二范围中元素的投影</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<div class="t-li1"><span class="t-li">1)</span> 返回作为序列 <code>[first2, last2)</code> （又称<i>针</i>），在分别应用 <code>proj1</code> 与 <code>proj2</code> 到两个序列的元素，再应用二元谓词 <code>pred</code> 比较投影后元素之后，于范围 <code>[first1, last1)</code> （又称<i>草堆</i>）中首次出现的 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">subrange</span></span></span> 值。
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<p>若找不到这种序列，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">subrange</span><span class="br0">{</span>last1, last1<span class="br0">}</span></span></span> 。</p>
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若待搜索范围（又称<i>针</i>）为空，即 <span class="t-c"><span class="mw-geshi cpp source-cpp">first2 <span class="sy1">==</span> last2</span></span> ，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">subrange</span><span class="br0">{</span>first1, first1<span class="br0">}</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，但返回类型为 <span class="t-c"><span class="mw-geshi cpp source-cpp">ranges<span class="sy4">::</span><span class="me2">borrowed_subrange_t</span><span class="sy1"><</span>R1<span class="sy1">></span></span></span> 。</div>
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<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
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<p>至多应用 <code>S*N</code> 次对应的谓词和各自的投影，其中<br />
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<span class="t-v">(1)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">S <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>first2, last2<span class="br0">)</span></span></span> 而 <span class="t-c"><span class="mw-geshi cpp source-cpp">N <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>first1, last1<span class="br0">)</span></span></span> ；<br />
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<span class="t-v">(2)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">S <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>r2<span class="br0">)</span></span></span> 而 <span class="t-c"><span class="mw-geshi cpp source-cpp">N <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">distance</span><span class="br0">(</span>r1<span class="br0">)</span></span></span> 。</p>
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<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>
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<table class="eq-fun-cpp-table">
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<tr>
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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="kw1">struct</span> search_fn
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<span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">forward_iterator</span> I1, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I1<span class="sy1">></span> S1,
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std<span class="sy4">::</span><span class="me2">forward_iterator</span> I2, std<span class="sy4">::</span><span class="me2">sentinel_for</span><span class="sy1"><</span>I2<span class="sy1">></span> S2,
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<span class="kw1">class</span> Pred <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">equal_to</span>,
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<span class="kw1">class</span> Proj1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,
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<span class="kw1">class</span> Proj2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span><span class="sy1">></span>
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requires std<span class="sy4">::</span><span class="me2">indirectly_comparable</span><span class="sy1"><</span>I1, I2, Pred, Proj1, Proj2<span class="sy1">></span>
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">subrange</span><span class="sy1"><</span>I1<span class="sy1">></span>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>I1 first1, S1 last1, I2 first2, S2 last2, Pred pred <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>,
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Proj1 proj1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj2 proj2 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="sy4">;;</span> <span class="sy2">++</span>first1<span class="br0">)</span> <span class="br0">{</span>
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I1 it1 <span class="sy1">=</span> first1<span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span>I2 it2 <span class="sy1">=</span> first2<span class="sy4">;;</span> <span class="sy2">++</span>it1, <span class="sy2">++</span>it2<span class="br0">)</span> <span class="br0">{</span>
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<span class="kw1">if</span> <span class="br0">(</span>it2 <span class="sy1">==</span> last2<span class="br0">)</span> <span class="kw1">return</span> <span class="br0">{</span>first1, it1<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>it1 <span class="sy1">==</span> last1<span class="br0">)</span> <span class="kw1">return</span> <span class="br0">{</span>it1, it1<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span><span class="sy3">!</span><a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>pred, <a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>proj1, <span class="sy2">*</span>it1<span class="br0">)</span>, <a href="cpp-utility-functional-invoke.html"><span class="kw1058">std::<span class="me2">invoke</span></span></a><span class="br0">(</span>proj2, <span class="sy2">*</span>it2<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
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<span class="kw1">break</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span>
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<span class="br0">}</span>
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<span class="kw1">template</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">forward_range</span> R1, ranges<span class="sy4">::</span><span class="me2">forward_range</span> R2,
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<span class="kw1">class</span> Pred <span class="sy1">=</span> ranges<span class="sy4">::</span><span class="me2">equal_to</span>,
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<span class="kw1">class</span> Proj1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span>,
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<span class="kw1">class</span> Proj2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">identity</span><span class="sy1">></span>
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requires std<span class="sy4">::</span><span class="me2">indirectly_comparable</span><span class="sy1"><</span>ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R1<span class="sy1">></span>,
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ranges<span class="sy4">::</span><span class="me2">iterator_t</span><span class="sy1"><</span>R2<span class="sy1">></span>, Pred, Proj1, Proj2<span class="sy1">></span>
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<span class="kw4">constexpr</span> ranges<span class="sy4">::</span><span class="me2">borrowed_subrange_t</span><span class="sy1"><</span>R1<span class="sy1">></span>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span>R1<span class="sy3">&&</span> r1, R2<span class="sy3">&&</span> r2, Pred pred <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>,
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Proj1 proj1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span>, Proj2 proj2 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="br0">)</span> <span class="kw4">const</span> <span class="br0">{</span>
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<span class="kw1">return</span> <span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span><span class="br0">(</span>ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r1<span class="br0">)</span>, ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r1<span class="br0">)</span>,
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ranges<span class="sy4">::</span><span class="me2">begin</span><span class="br0">(</span>r2<span class="br0">)</span>, ranges<span class="sy4">::</span><span class="me2">end</span><span class="br0">(</span>r2<span class="br0">)</span>,
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std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>pred<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>proj1<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>proj2<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw1">inline</span> <span class="kw4">constexpr</span> search_fn search<span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></pre></div>
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</div>
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</td>
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</tr>
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</table>
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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 <algorithm></span>
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<span class="co2">#include <cctype></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 <string_view></span>
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<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">;</span>
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<span class="kw4">void</span> print<span class="br0">(</span><span class="kw4">int</span> id, <span class="kw4">const</span> <span class="kw4">auto</span><span class="sy3">&</span> haystack, <span class="kw4">const</span> <span class="kw4">auto</span><span class="sy3">&</span> needle, <span class="kw4">const</span> <span class="kw4">auto</span><span class="sy3">&</span> found<span class="br0">)</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> id <span class="sy1"><<</span> <span class="st0">"). search(<span class="es1">\"</span>"</span> <span class="sy1"><<</span> haystack <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span>, <span class="es1">\"</span>"</span> <span class="sy1"><<</span> needle <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span>); "</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">auto</span> first <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>haystack.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, found.<span class="me1">begin</span><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> last <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>haystack.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, found.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>found.<span class="me1">empty</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</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">"not found;"</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">else</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">"found: <span class="es1">\"</span>"</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">const</span> <span class="kw4">auto</span> x<span class="sy4">:</span> found<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> x<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">\"</span>;"</span><span class="sy4">;</span>
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<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">" subrange: {"</span> <span class="sy1"><<</span> first <span class="sy1"><<</span> <span class="st0">", "</span> <span class="sy1"><<</span> last <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>
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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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<span class="kw4">constexpr</span> <span class="kw4">auto</span> haystack <span class="br0">{</span><span class="st0">"abcd abcd"</span>sv<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> needle <span class="br0">{</span><span class="st0">"bcd"</span>sv<span class="br0">}</span><span class="sy4">;</span>
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<span class="co1">// 搜索使用迭代器对 begin()/end() ：</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> found1 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">search</span><span class="br0">(</span>
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haystack.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, haystack.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>,
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needle.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, needle.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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print<span class="br0">(</span><span class="nu0">1</span>, haystack, needle, found1<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 搜索使用范围 r1、 r2 ：</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> found2 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">search</span><span class="br0">(</span>haystack, needle<span class="br0">)</span><span class="sy4">;</span>
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print<span class="br0">(</span><span class="nu0">2</span>, haystack, needle, found2<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// ‘针’范围为空：</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> none <span class="br0">{</span><span class="st0">""</span>sv<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> found3 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">search</span><span class="br0">(</span>haystack, none<span class="br0">)</span><span class="sy4">;</span>
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print<span class="br0">(</span><span class="nu0">3</span>, haystack, none, found3<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 不会找到‘针’范围：</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> awl <span class="br0">{</span><span class="st0">"efg"</span>sv<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> found4 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">search</span><span class="br0">(</span>haystack, awl<span class="br0">)</span><span class="sy4">;</span>
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print<span class="br0">(</span><span class="nu0">4</span>, haystack, awl, found4<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 搜索使用定制比较器与投影：</span>
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<span class="kw4">constexpr</span> <span class="kw4">auto</span> bodkin <span class="br0">{</span><span class="st0">"234"</span>sv<span class="br0">}</span><span class="sy4">;</span>
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<span class="kw4">auto</span> found5 <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">ranges</span><span class="sy4">::</span><span class="me2">search</span><span class="br0">(</span>haystack, bodkin,
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<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> x, <span class="kw4">const</span> <span class="kw4">int</span> y<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> x <span class="sy1">==</span> y<span class="sy4">;</span> <span class="br0">}</span>, <span class="co1">// pred</span>
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<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> x<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">toupper</span><span class="br0">(</span>x<span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span>, <span class="co1">// proj1</span>
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<span class="br0">[</span><span class="br0">]</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> y<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> y <span class="sy2">+</span> <span class="st0">'A'</span> <span class="sy2">-</span> <span class="st0">'1'</span><span class="sy4">;</span> <span class="br0">}</span> <span class="co1">// proj2</span>
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<span class="br0">)</span><span class="sy4">;</span>
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print<span class="br0">(</span><span class="nu0">5</span>, haystack, bodkin, found5<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</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">1). search("abcd abcd", "bcd"); found: "bcd"; subrange: {1, 4}
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2). search("abcd abcd", "bcd"); found: "bcd"; subrange: {1, 4}
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3). search("abcd abcd", ""); not found; subrange: {0, 0}
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4). search("abcd abcd", "efg"); not found; subrange: {9, 9}
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5). search("abcd abcd", "234"); found: "bcd"; subrange: {1, 4}</pre></div>
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</div>
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</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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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-adjacent_find.html"><span class="t-lines"><span>ranges::adjacent_find</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>查找首对相邻的相同（或满足给定谓词的）元素<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-find.html"><span class="t-lines"><span>ranges::find</span><span>ranges::find_if</span><span>ranges::find_if_not</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><span class="t-mark-rev t-since-cxx20">(C++20)</span></span><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>寻找首个满足特定判别标准的元素<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-find_end.html"><span class="t-lines"><span>ranges::find_end</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>在特定范围中寻找最后出现的元素序列<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-find_first_of.html"><span class="t-lines"><span>ranges::find_first_of</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>搜索元素集合中的任一元素<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-includes.html"><span class="t-lines"><span>ranges::includes</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>若一个序列是另一个的子列则返回 <code>true</code><br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-mismatch.html"><span class="t-lines"><span>ranges::mismatch</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>寻找两个范围出现不同的首个位置<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-ranges-search_n.html"><span class="t-lines"><span>ranges::search_n</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>在范围中搜索一定量的某个元素的连续副本<br />
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<span class="t-mark">(niebloid)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-algorithm-search.html"><span class="t-lines"><span>search</span></span></a></div>
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</div>
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</td>
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<td>搜索一个元素范围<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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