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<h1><a class="toc-backref" href="./querying-algorithms.html#id1476">find_if</a></h1>
<div class="section" id="id543">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
template&lt;
      typename Sequence
    , typename Pred
    &gt;
struct <a href="./find-if.html" class="identifier">find_if</a>
{
    typedef <em>unspecified</em> type;
};
</pre>
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<div class="section" id="id544">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>Returns an iterator to the first element in <tt class="literal"><span class="pre">Sequence</span></tt> that satisfies
the predicate <tt class="literal"><span class="pre">Pred</span></tt>.</p>
</div>
<div class="section" id="id545">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/find_if.hpp" class="header">boost/mpl/find_if.hpp</a>&gt;
</pre>
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<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<tr><th class="head">Parameter</th>
<th class="head">Requirement</th>
<th class="head">Description</th>
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<tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td>
<td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td>
<td>A sequence to search in.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">Pred</span></tt></td>
<td>Unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td>
<td>A search condition.</td>
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<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt> and unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a> <tt class="literal"><span class="pre">pred</span></tt>:</p>
<pre class="literal-block">
typedef <a href="./find-if.html" class="identifier">find_if</a>&lt;s,pred&gt;::type i;
</pre>
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<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>.</p>
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</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">i</span></tt> is the first iterator in the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt>) such that</p>
<pre class="literal-block">
<a href="./apply.html" class="identifier">apply</a>&lt; pred,<a href="./deref.html" class="identifier">deref</a>&lt;i&gt;::type &gt;::type::value == true
</pre>
<p class="last">If no such iterator exists, <tt class="literal"><span class="pre">i</span></tt> is identical to <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt>.</p>
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<div class="section" id="id548">
<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
<p>Linear. At most <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::value</span></tt> applications of <tt class="literal"><span class="pre">pred</span></tt>.</p>
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<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
typedef <a href="./vector.html" class="identifier">vector</a>&lt;char,int,unsigned,long,unsigned long&gt; types;
typedef <a href="./find-if.html" class="identifier">find_if</a>&lt;types, is_same&lt;<a href="./placeholders.html" class="identifier">_1</a>,unsigned&gt; &gt;::type iter;

<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt; <a href="./deref.html" class="identifier">deref</a>&lt;iter&gt;::type, unsigned &gt; ));
<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( iter::pos::value, ==, 2 );
</pre>
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<div class="section" id="id550">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./querying-algorithms.html">Querying Algorithms</a>, <a class="reference internal" href="./find.html">find</a>, <a class="reference internal" href="./count-if.html">count_if</a>, <a class="reference internal" href="./lower-bound.html">lower_bound</a></p>
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