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<div class="section" id="replace-if">
<h1><a class="toc-backref" href="./transformation-algorithms.html#id1490">replace_if</a></h1>
<div class="section" id="id651">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
template&lt;
      typename Sequence
    , typename Pred
    , typename NewType
    , typename In = <em>unspecified</em>
    &gt;
struct <a href="./replace-if.html" class="identifier">replace_if</a>
{
    typedef <em>unspecified</em> type;
};
</pre>
</div>
<div class="section" id="id652">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>Returns a copy of the original sequence where every type that satisfies
the predicate <tt class="literal"><span class="pre">Pred</span></tt> has been replaced with <tt class="literal"><span class="pre">NewType</span></tt>.</p>
<p>[<em>Note:</em> This wording applies to a no-inserter version(s) of the algorithm. See the
<cite>Expression semantics</cite> subsection for a precise specification of the algorithm's
details in all cases — <em>end note</em>]</p>
</div>
<div class="section" id="id653">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/replace_if.hpp" class="header">boost/mpl/replace_if.hpp</a>&gt;
</pre>
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<div class="section" id="id654">
<h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
<p><a class="reference internal" href="./reversible-algorithm.html">Reversible Algorithm</a></p>
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<div class="section" id="id655">
<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>
</tr>
</thead>
<tbody valign="top">
<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>An original sequence.</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 replacement condition.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">NewType</span></tt></td>
<td>Any type</td>
<td>A type to replace with.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">In</span></tt></td>
<td><a class="reference internal" href="./inserter.html">Inserter</a></td>
<td>An inserter.</td>
</tr>
</tbody>
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<div class="section" id="id656">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>The semantics of an expression are defined only
where they differ from, or are not defined in <a class="reference internal" href="./reversible-algorithm.html">Reversible Algorithm</a>.</p>
<p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt>, an unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a> <tt class="literal"><span class="pre">pred</span></tt>,
an <a class="reference internal" href="./inserter.html">Inserter</a> <tt class="literal"><span class="pre">in</span></tt>, and arbitrary type <tt class="literal"><span class="pre">x</span></tt>:</p>
<pre class="literal-block">
typedef <a href="./replace-if.html" class="identifier">replace_if</a>&lt;s,pred,x,in&gt;::type r;
</pre>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
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<tbody valign="top">
<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">A type.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
<pre class="last literal-block">
typedef <a href="./lambda.html" class="identifier">lambda</a>&lt;pred&gt;::type p;
typedef <a href="./transform.html" class="identifier">transform</a>&lt; s, <a href="./if.html" class="identifier">if_</a>&lt; apply_wrap1&lt;p,<a href="./placeholders.html" class="identifier">_1</a>&gt;,x,<a href="./placeholders.html" class="identifier">_1</a>&gt;, in &gt;::type r;
</pre>
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<div class="section" id="id657">
<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
<p>Linear. Performs exactly <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>, and at most
<tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::value</span></tt> insertions.</p>
</div>
<div class="section" id="id658">
<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
typedef <a href="./vector-c.html" class="identifier">vector_c</a>&lt;int,1,4,5,2,7,5,3,5&gt; numbers;
typedef <a href="./vector-c.html" class="identifier">vector_c</a>&lt;int,1,4,0,2,0,0,3,0&gt; expected;
typedef <a href="./replace-if.html" class="identifier">replace_if</a>&lt; numbers, <a href="./greater.html" class="identifier">greater</a>&lt;_,<a href="./int.html" class="identifier">int_</a>&lt;4&gt; &gt;, <a href="./int.html" class="identifier">int_</a>&lt;0&gt; &gt;::type result;

<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a>&lt; result,expected, <a href="./equal-to.html" class="identifier">equal_to</a>&lt;_,_&gt; > ));
</pre>
</div>
<div class="section" id="id659">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./transformation-algorithms.html">Transformation Algorithms</a>, <a class="reference internal" href="./reversible-algorithm.html">Reversible Algorithm</a>, <a class="reference internal" href="./reverse-replace-if.html">reverse_replace_if</a>, <a class="reference internal" href="./replace.html">replace</a>, <a class="reference internal" href="./remove-if.html">remove_if</a>, <a class="reference internal" href="./transform.html">transform</a></p>
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