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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="the_boost_algorithm_library.CXX11.one_of"></a><a class="link" href="one_of.html" title="one_of">one_of</a>
  28 </h3></div></div></div>
  29 <p>
  30         The header file 'boost/algorithm/cxx11/one_of.hpp' contains four variants
  31         of a single algorithm, <code class="computeroutput"><span class="identifier">one_of</span></code>.
  32         The algorithm tests the elements of a sequence and returns true if exactly
  33         one of the elements in the sequence has a particular property.
  34       </p>
  35 <p>
  36         The routine <code class="computeroutput"><span class="identifier">one_of</span></code> takes
  37         a sequence and a predicate. It will return true if the predicate returns
  38         true for one element in the sequence.
  39       </p>
  40 <p>
  41         The routine <code class="computeroutput"><span class="identifier">one_of_equal</span></code>
  42         takes a sequence and a value. It will return true if one element in the sequence
  43         compares equal to the passed in value.
  44       </p>
  45 <p>
  46         Both routines come in two forms; the first one takes two iterators to define
  47         the range. The second form takes a single range parameter, and uses Boost.Range
  48         to traverse it.
  49       </p>
  50 <h5>
  51 <a name="the_boost_algorithm_library.CXX11.one_of.h0"></a>
  52         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.one_of.interface"></a></span><a class="link" href="one_of.html#the_boost_algorithm_library.CXX11.one_of.interface">interface</a>
  53       </h5>
  54 <p>
  55         The function <code class="computeroutput"><span class="identifier">one_of</span></code> returns
  56         true if the predicate returns true for one item in the sequence. There are
  57         two versions; one takes two iterators, and the other takes a range.
  58       </p>
  59 <p>
  60 </p>
  61 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
  62 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">InputIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Predicate</span><span class="special">&gt;</span>
  63         <span class="keyword">bool</span> <span class="identifier">one_of</span> <span class="special">(</span> <span class="identifier">InputIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">InputIterator</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">Predicate</span> <span class="identifier">p</span> <span class="special">);</span>
  64 <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>
  65         <span class="keyword">bool</span> <span class="identifier">one_of</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>
  66 <span class="special">}}</span>
  67 </pre>
  68 <p>
  69       </p>
  70 <p>
  71         The function <code class="computeroutput"><span class="identifier">one_of_equal</span></code>
  72         is similar to <code class="computeroutput"><span class="identifier">one_of</span></code>, but
  73         instead of taking a predicate to test the elements of the sequence, it takes
  74         a value to compare against.
  75       </p>
  76 <p>
  77 </p>
  78 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">algorithm</span> <span class="special">{</span>
  79 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">InputIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">V</span><span class="special">&gt;</span>
  80         <span class="keyword">bool</span> <span class="identifier">one_of_equal</span> <span class="special">(</span> <span class="identifier">InputIterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">InputIterator</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">V</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="identifier">val</span> <span class="special">);</span>
  81 <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">V</span><span class="special">&gt;</span>
  82         <span class="keyword">bool</span> <span class="identifier">one_of_equal</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">V</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="identifier">val</span> <span class="special">);</span>
  83 <span class="special">}}</span>
  84 </pre>
  85 <p>
  86       </p>
  87 <h5>
  88 <a name="the_boost_algorithm_library.CXX11.one_of.h1"></a>
  89         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.one_of.examples"></a></span><a class="link" href="one_of.html#the_boost_algorithm_library.CXX11.one_of.examples">Examples</a>
  90       </h5>
  91 <p>
  92         Given the container <code class="computeroutput"><span class="identifier">c</span></code> containing
  93         <code class="computeroutput"><span class="special">{</span> <span class="number">0</span><span class="special">,</span> <span class="number">1</span><span class="special">,</span>
  94         <span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">,</span> <span class="number">14</span><span class="special">,</span> <span class="number">15</span> <span class="special">}</span></code>,
  95         then
  96 </p>
  97 <pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">isOdd</span> <span class="special">(</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">i</span> <span class="special">%</span> <span class="number">2</span> <span class="special">==</span> <span class="number">1</span><span class="special">;</span> <span class="special">}</span>
  98 <span class="keyword">bool</span> <span class="identifier">lessThan10</span> <span class="special">(</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">i</span> <span class="special">&lt;</span> <span class="number">10</span><span class="special">;</span> <span class="special">}</span>
  99
 100 <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">algorithm</span><span class="special">;</span>
 101 <span class="identifier">one_of</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">,</span> <span class="identifier">isOdd</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">false</span>
 102 <span class="identifier">one_of</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span> <span class="special">(),</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">end</span> <span class="special">(),</span> <span class="identifier">lessThan10</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">false</span>
 103 <span class="identifier">one_of</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span> <span class="special">()</span> <span class="special">+</span> <span class="number">3</span><span class="special">,</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">end</span> <span class="special">(),</span> <span class="identifier">lessThan10</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
 104 <span class="identifier">one_of</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">end</span> <span class="special">(),</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">end</span> <span class="special">(),</span> <span class="identifier">isOdd</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">false</span>  <span class="comment">// empty range</span>
 105 <span class="identifier">one_of_equal</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">,</span> <span class="number">3</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">true</span>
 106 <span class="identifier">one_of_equal</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span> <span class="special">(),</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span> <span class="special">()</span> <span class="special">+</span> <span class="number">3</span><span class="special">,</span> <span class="number">3</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">false</span>
 107 <span class="identifier">one_of_equal</span> <span class="special">(</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span> <span class="special">(),</span> <span class="identifier">c</span><span class="special">.</span><span class="identifier">begin</span> <span class="special">(),</span> <span class="number">99</span> <span class="special">)</span> <span class="special">--&gt;</span> <span class="keyword">false</span>  <span class="comment">// empty range</span>
 108 </pre>
 109 <p>
 110       </p>
 111 <h5>
 112 <a name="the_boost_algorithm_library.CXX11.one_of.h2"></a>
 113         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.one_of.iterator_requirements"></a></span><a class="link" href="one_of.html#the_boost_algorithm_library.CXX11.one_of.iterator_requirements">Iterator
 114         Requirements</a>
 115       </h5>
 116 <p>
 117         <code class="computeroutput"><span class="identifier">one_of</span></code> and <code class="computeroutput"><span class="identifier">one_of_equal</span></code> work on all iterators except
 118         output iterators.
 119       </p>
 120 <h5>
 121 <a name="the_boost_algorithm_library.CXX11.one_of.h3"></a>
 122         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.one_of.complexity"></a></span><a class="link" href="one_of.html#the_boost_algorithm_library.CXX11.one_of.complexity">Complexity</a>
 123       </h5>
 124 <p>
 125         All of the variants of <code class="computeroutput"><span class="identifier">one_of</span></code>
 126         and <code class="computeroutput"><span class="identifier">one_of_equal</span></code> run in
 127         <span class="emphasis"><em>O(N)</em></span> (linear) time; that is, they compare against each
 128         element in the list once. If more than one of the elements in the sequence
 129         satisfy the condition, then algorithm will return false immediately, without
 130         examining the remaining members of the sequence.
 131       </p>
 132 <h5>
 133 <a name="the_boost_algorithm_library.CXX11.one_of.h4"></a>
 134         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.one_of.exception_safety"></a></span><a class="link" href="one_of.html#the_boost_algorithm_library.CXX11.one_of.exception_safety">Exception
 135         Safety</a>
 136       </h5>
 137 <p>
 138         All of the variants of <code class="computeroutput"><span class="identifier">one_of</span></code>
 139         and <code class="computeroutput"><span class="identifier">one_of_equal</span></code> take their
 140         parameters by value or const reference, and do not depend upon any global
 141         state. Therefore, all the routines in this file provide the strong exception
 142         guarantee.
 143       </p>
 144 <h5>
 145 <a name="the_boost_algorithm_library.CXX11.one_of.h5"></a>
 146         <span class="phrase"><a name="the_boost_algorithm_library.CXX11.one_of.notes"></a></span><a class="link" href="one_of.html#the_boost_algorithm_library.CXX11.one_of.notes">Notes</a>
 147       </h5>
 148 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 149 <li class="listitem">
 150             <code class="computeroutput"><span class="identifier">one_of</span></code> and <code class="computeroutput"><span class="identifier">one_of_equal</span></code> both return false for
 151             empty ranges, no matter what is passed to test against.
 152           </li>
 153 <li class="listitem">
 154             The second parameter to <code class="computeroutput"><span class="identifier">one_of_equal</span></code>
 155             is a template parameter, rather than deduced from the first parameter
 156             (<code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special">&lt;</span><span class="identifier">InputIterator</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code>) because that allows more
 157             flexibility for callers, and takes advantage of built-in comparisons
 158             for the type that is pointed to by the iterator. The function is defined
 159             to return true if, for one element in the sequence, the expression <code class="computeroutput"><span class="special">*</span><span class="identifier">iter</span> <span class="special">==</span> <span class="identifier">val</span></code>
 160             evaluates to true (where <code class="computeroutput"><span class="identifier">iter</span></code>
 161             is an iterator to each element in the sequence)
 162           </li>
 163 </ul></div>
 164 </div>
 165 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 166 <td align="left"></td>
 167 <td align="right"><div class="copyright-footer">Copyright &#169; 2010-2012 Marshall Clow<p>
 168         Distributed under the Boost Software License, Version 1.0. (See accompanying
 169         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>)
 170       </p>
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