libs/algorithm/doc/html/the_boost_algorithm_library/Misc/is_palindrome.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>is_palindrome</title>
   5 <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
   6 <meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
   7 <link rel="home" href="../../index.html" title="The Boost Algorithm Library">
   8 <link rel="up" href="../../algorithm/Misc.html" title="Other Algorithms">
   9 <link rel="prev" href="hex.html" title="hex">
  10 <link rel="next" href="is_partitioned_until.html" title="is_partitioned_until">
  11 </head>
  12 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  13 <table cellpadding="2" width="100%"><tr>
  14 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
  15 <td align="center"><a href="../../../../../../index.html">Home</a></td>
  16 <td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
  17 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  19 <td align="center"><a href="../../../../../../more/index.htm">More</a></td>
  20 </tr></table>
  21 <hr>
  22 <div class="spirit-nav">
  23 <a accesskey="p" href="hex.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../algorithm/Misc.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="is_partitioned_until.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
  24 </div>
  25 <div class="section">
  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="the_boost_algorithm_library.Misc.is_palindrome"></a><a class="link" href="is_palindrome.html" title="is_palindrome">is_palindrome</a>
  28 </h3></div></div></div>
  29 <p>
  30         The header file 'is_palindrome.hpp' contains six variants of a single algorithm,
  31         is_palindrome. The algorithm tests the sequence and returns true if the sequence
  32         is a palindrome; i.e, it is identical when traversed either backwards or
  33         frontwards.
  34       </p>
  35 <p>
  36         The routine <code class="computeroutput"><span class="identifier">is_palindrome</span></code>
  37         takes a sequence and, optionally, a predicate. It will return true if the
  38         predicate returns true for tested elements by algorithm in the sequence.
  39       </p>
  40 <p>
  41         The routine come in 6 forms; the first one takes two iterators to define
  42         the range. The second form takes two iterators to define the range and a
  43         predicate. The third form takes a single range parameter, and uses Boost.Range
  44         to traverse it. The fourth form takes a single range parameter ( uses Boost.Range
  45         to traverse it) and a predicate. The fifth form takes a single C-string and
  46         a predicate. The sixth form takes a single C-string.
  47       </p>
  48 <h5>
  49 <a name="the_boost_algorithm_library.Misc.is_palindrome.h0"></a>
  50         <span class="phrase"><a name="the_boost_algorithm_library.Misc.is_palindrome.interface"></a></span><a class="link" href="is_palindrome.html#the_boost_algorithm_library.Misc.is_palindrome.interface">interface</a>
  51       </h5>
  52 <p>
  53         The function <code class="computeroutput"><span class="identifier">is_palindrome</span></code>
  54         returns true if the predicate returns true any tested by algorithm items
  55         in the sequence. There are six versions: 1) takes two iterators. 2) takes
  56         two iterators and a predicate. 3) takes a range. 4) takes a range and a predicate.
  57         5) takes a C-string and a predicate. 6) takes a C-string.
  58       </p>
  59 <p>
  60 </p>
  61 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">BidirectionalIterator</span><span class="special">&gt;</span>
  62         <span class="keyword">bool</span> <span class="identifier">is_palindrome</span> <span class="special">(</span> <span class="identifier">BidirectionalIterator</span> <span class="identifier">begin</span><span class="special">,</span> <span class="identifier">BidirectionalIterator</span> <span class="identifier">end</span> <span class="special">);</span>
  63 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">BidirectionalIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Predicate</span><span class="special">&gt;</span>
  64         <span class="keyword">bool</span> <span class="identifier">is_palindrome</span> <span class="special">(</span> <span class="identifier">BidirectionalIterator</span> <span class="identifier">begin</span><span class="special">,</span> <span class="identifier">BidirectionalIterator</span> <span class="identifier">end</span><span class="special">,</span> <span class="identifier">Predicate</span> <span class="identifier">p</span> <span class="special">);</span>
  65 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">&gt;</span>
  66         <span class="keyword">bool</span> <span class="identifier">is_palindrome</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range</span> <span class="special">&amp;</span><span class="identifier">r</span> <span class="special">);</span>
  67 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Predicate</span><span class="special">&gt;</span>
  68         <span class="keyword">bool</span> <span class="identifier">is_palindrome</span> <span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Range</span> <span class="special">&amp;</span><span class="identifier">r</span><span class="special">,</span> <span class="identifier">Predicate</span> <span class="identifier">p</span> <span class="special">);</span>
  69 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Predicate</span><span class="special">&gt;</span>
  70         <span class="keyword">bool</span> <span class="identifier">is_palindrome</span> <span class="special">(</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">str</span><span class="special">,</span> <span class="identifier">Predicate</span> <span class="identifier">p</span> <span class="special">);</span>
  71 <span class="keyword">bool</span> <span class="identifier">is_palindrome</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">str</span><span class="special">);</span>
  72 </pre>
  73 <p>
  74       </p>
  75 <h5>
  76 <a name="the_boost_algorithm_library.Misc.is_palindrome.h1"></a>
  77         <span class="phrase"><a name="the_boost_algorithm_library.Misc.is_palindrome.examples"></a></span><a class="link" href="is_palindrome.html#the_boost_algorithm_library.Misc.is_palindrome.examples">Examples</a>
  78       </h5>
  79 <p>
  80         Given the containers: const std::list&lt;int&gt; empty, const std::vector&lt;char&gt;
  81         singleElement{'z'}, int oddNonPalindrome[] = {3,2,2}, const int oddPalindrome[]
  82         = {1,2,3,2,1}, const int evenPalindrome[] = {1,2,2,1}, int evenNonPalindrome[]
  83         = {1,4,8,8}, then
  84 </p>
  85 <pre class="programlisting"><span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">empty</span><span class="special">))</span>  <span class="special">--&gt;</span> <span class="keyword">true</span> <span class="comment">//empty range                                                                       </span>
  86 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">singleElement</span><span class="special">))</span>  <span class="special">--&gt;</span> <span class="keyword">true</span>
  87 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">oddNonPalindrome</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">oddNonPalindrome</span><span class="special">)))</span> <span class="special">--&gt;</span> <span class="keyword">false</span>
  88 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">evenPalindrome</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">evenPalindrome</span><span class="special">)))</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
  89 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">empty</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">empty</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">functorComparator</span><span class="special">()))</span> <span class="special">--&gt;</span> <span class="keyword">true</span> <span class="comment">//empty range                             </span>
  90 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">oddNonPalindrome</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">oddNonPalindrome</span><span class="special">),</span> <span class="identifier">funcComparator</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;))</span> <span class="special">--&gt;</span> <span class="keyword">false</span>
  91 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">oddPalindrome</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">oddPalindrome</span><span class="special">))</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
  92 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">evenPalindrome</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">equal_to</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;()))</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
  93 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">evenNonPalindrome</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">evenNonPalindrome</span><span class="special">))</span> <span class="special">--&gt;</span> <span class="keyword">false</span>
  94 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="string">"a"</span><span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
  95 <span class="identifier">is_palindrome</span><span class="special">(</span><span class="string">"aba"</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">equal_to</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;())</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
  96 </pre>
  97 <p>
  98       </p>
  99 <h5>
 100 <a name="the_boost_algorithm_library.Misc.is_palindrome.h2"></a>
 101         <span class="phrase"><a name="the_boost_algorithm_library.Misc.is_palindrome.iterator_requirements"></a></span><a class="link" href="is_palindrome.html#the_boost_algorithm_library.Misc.is_palindrome.iterator_requirements">Iterator
 102         Requirements</a>
 103       </h5>
 104 <p>
 105         <code class="computeroutput"><span class="identifier">is_palindrome</span></code> work on Bidirectional
 106         and RandomAccess iterators.
 107       </p>
 108 <h5>
 109 <a name="the_boost_algorithm_library.Misc.is_palindrome.h3"></a>
 110         <span class="phrase"><a name="the_boost_algorithm_library.Misc.is_palindrome.complexity"></a></span><a class="link" href="is_palindrome.html#the_boost_algorithm_library.Misc.is_palindrome.complexity">Complexity</a>
 111       </h5>
 112 <p>
 113         All of the variants of <code class="computeroutput"><span class="identifier">is_palindrome</span></code>
 114         run in <span class="emphasis"><em>O(N)</em></span> (linear) time; that is, they compare against
 115         each element in the list once. If any of the comparisons not succeed, the
 116         algorithm will terminate immediately, without examining the remaining members
 117         of the sequence.
 118       </p>
 119 <h5>
 120 <a name="the_boost_algorithm_library.Misc.is_palindrome.h4"></a>
 121         <span class="phrase"><a name="the_boost_algorithm_library.Misc.is_palindrome.exception_safety"></a></span><a class="link" href="is_palindrome.html#the_boost_algorithm_library.Misc.is_palindrome.exception_safety">Exception
 122         Safety</a>
 123       </h5>
 124 <p>
 125         All of the variants of <code class="computeroutput"><span class="identifier">is_palindrome</span></code>
 126         take their parameters by value, const pointer or const reference, and do
 127         not depend upon any global state. Therefore, all the routines in this file
 128         provide the strong exception guarantee.
 129       </p>
 130 <h5>
 131 <a name="the_boost_algorithm_library.Misc.is_palindrome.h5"></a>
 132         <span class="phrase"><a name="the_boost_algorithm_library.Misc.is_palindrome.notes"></a></span><a class="link" href="is_palindrome.html#the_boost_algorithm_library.Misc.is_palindrome.notes">Notes</a>
 133       </h5>
 134 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 135 <li class="listitem">
 136             <code class="computeroutput"><span class="identifier">is_palindrome</span></code> returns
 137             true for empty ranges, const char* null pointers and for single element
 138             ranges.
 139           </li>
 140 <li class="listitem">
 141             If you use version of 'is_palindrome' without custom predicate, 'is_palindrome'
 142             uses default 'operator==()' for elements.
 143           </li>
 144 <li class="listitem">
 145             Be careful with using not null pointer 'const char*' without '\0' - if
 146             you use it with 'is_palindrome', it's a undefined behaviour.
 147           </li>
 148 </ul></div>
 149 </div>
 150 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 151 <td align="left"></td>
 152 <td align="right"><div class="copyright-footer">Copyright &#169; 2010-2012 Marshall Clow<p>
 153         Distributed under the Boost Software License, Version 1.0. (See accompanying
 154         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
 155       </p>
 156 </div></td>
 157 </tr></table>
 158 <hr>
 159 <div class="spirit-nav">
 160 <a accesskey="p" href="hex.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../algorithm/Misc.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="is_partitioned_until.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 161 </div>
 162 </body>
 163 </html>