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<div class="titlepage"><div><div><h3 class="title">
<a name="the_boost_algorithm_library.CXX11.one_of"></a><a class="link" href="one_of.html" title="one_of">one_of</a>
</h3></div></div></div>
<p>
        The header file 'boost/algorithm/cxx11/one_of.hpp' contains four variants
        of a single algorithm, <code class="computeroutput"><span class="identifier">one_of</span></code>.
        The algorithm tests the elements of a sequence and returns true if exactly
        one of the elements in the sequence has a particular property.
      </p>
<p>
        The routine <code class="computeroutput"><span class="identifier">one_of</span></code> takes
        a sequence and a predicate. It will return true if the predicate returns
        true for one element in the sequence.
      </p>
<p>
        The routine <code class="computeroutput"><span class="identifier">one_of_equal</span></code>
        takes a sequence and a value. It will return true if one element in the sequence
        compares equal to the passed in value.
      </p>
<p>
        Both routines come in two forms; the first one takes two iterators to define
        the range. The second form takes a single range parameter, and uses Boost.Range
        to traverse it.
      </p>
<h5>
<a name="the_boost_algorithm_library.CXX11.one_of.h0"></a>
        <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>
      </h5>
<p>
        The function <code class="computeroutput"><span class="identifier">one_of</span></code> returns
        true if the predicate returns true for one item in the sequence. There are
        two versions; one takes two iterators, and the other takes a range.
      </p>
<p>
</p>
<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>
<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>
	<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>
<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>
	<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>
<span class="special">}}</span>
</pre>
<p>
      </p>
<p>
        The function <code class="computeroutput"><span class="identifier">one_of_equal</span></code>
        is similar to <code class="computeroutput"><span class="identifier">one_of</span></code>, but
        instead of taking a predicate to test the elements of the sequence, it takes
        a value to compare against.
      </p>
<p>
</p>
<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>
<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>
	<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>
<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>
	<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>
<span class="special">}}</span>
</pre>
<p>
      </p>
<h5>
<a name="the_boost_algorithm_library.CXX11.one_of.h1"></a>
        <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>
      </h5>
<p>
        Given the container <code class="computeroutput"><span class="identifier">c</span></code> containing
        <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>
        <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>,
        then
</p>
<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>
<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>

<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">algorithm</span><span class="special">;</span>
<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>
<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>
<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>
<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>
<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>
<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>
<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>
</pre>
<p>
      </p>
<h5>
<a name="the_boost_algorithm_library.CXX11.one_of.h2"></a>
        <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
        Requirements</a>
      </h5>
<p>
        <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
        output iterators.
      </p>
<h5>
<a name="the_boost_algorithm_library.CXX11.one_of.h3"></a>
        <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>
      </h5>
<p>
        All of the variants of <code class="computeroutput"><span class="identifier">one_of</span></code>
        and <code class="computeroutput"><span class="identifier">one_of_equal</span></code> run in
        <span class="emphasis"><em>O(N)</em></span> (linear) time; that is, they compare against each
        element in the list once. If more than one of the elements in the sequence
        satisfy the condition, then algorithm will return false immediately, without
        examining the remaining members of the sequence.
      </p>
<h5>
<a name="the_boost_algorithm_library.CXX11.one_of.h4"></a>
        <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
        Safety</a>
      </h5>
<p>
        All of the variants of <code class="computeroutput"><span class="identifier">one_of</span></code>
        and <code class="computeroutput"><span class="identifier">one_of_equal</span></code> take their
        parameters by value or const reference, and do not depend upon any global
        state. Therefore, all the routines in this file provide the strong exception
        guarantee.
      </p>
<h5>
<a name="the_boost_algorithm_library.CXX11.one_of.h5"></a>
        <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>
      </h5>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            <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
            empty ranges, no matter what is passed to test against.
          </li>
<li class="listitem">
            The second parameter to <code class="computeroutput"><span class="identifier">one_of_equal</span></code>
            is a template parameter, rather than deduced from the first parameter
            (<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
            flexibility for callers, and takes advantage of built-in comparisons
            for the type that is pointed to by the iterator. The function is defined
            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>
            evaluates to true (where <code class="computeroutput"><span class="identifier">iter</span></code>
            is an iterator to each element in the sequence)
          </li>
</ul></div>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2010-2012 Marshall Clow<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        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>)
      </p>
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