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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.3.0: http://docutils.sourceforge.net/" />
<title>Transform Iterator</title>
<meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" />
<meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab, University of Hanover Institute for Transport Railway Operation and Construction" />
<meta name="date" content="2003-09-14" />
<meta name="copyright" content="Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved" />
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<div class="document" id="transform-iterator">
<h1 class="title">Transform Iterator</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<col class="docinfo-content" />
<tbody valign="top">
<tr><th class="docinfo-name">Author:</th>
<td>David Abrahams, Jeremy Siek, Thomas Witt</td></tr>
<tr><th class="docinfo-name">Contact:</th>
<td><a class="first reference" href="mailto:dave&#64;boost-consulting.com">dave&#64;boost-consulting.com</a>, <a class="reference" href="mailto:jsiek&#64;osl.iu.edu">jsiek&#64;osl.iu.edu</a>, <a class="last reference" href="mailto:witt&#64;ive.uni-hannover.de">witt&#64;ive.uni-hannover.de</a></td></tr>
<tr><th class="docinfo-name">Organization:</th>
<td><a class="first reference" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="reference" href="http://www.osl.iu.edu">Open Systems
Lab</a>, University of Hanover <a class="last reference" href="http://www.ive.uni-hannover.de">Institute for Transport
Railway Operation and Construction</a></td></tr>
<tr><th class="docinfo-name">Date:</th>
<td>2003-09-14</td></tr>
<tr><th class="docinfo-name">Copyright:</th>
<td>Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved</td></tr>
</tbody>
</table>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
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<tr class="field"><th class="field-name">abstract:</th><td class="field-body"></td>
</tr>
</tbody>
</table>
<p>The transform iterator adapts an iterator by applying some function
object to the result of dereferencing the iterator. In other words,
the <tt class="literal"><span class="pre">operator*</span></tt> of the transform iterator first dereferences the
base iterator, passes the result of this to the function object, and
then returns the result.</p>
<div class="contents topic" id="table-of-contents">
<p class="topic-title"><a name="table-of-contents">Table of Contents</a></p>
<ul class="simple">
<li><a class="reference" href="#transform-iterator-requirements" id="id1" name="id1"><tt class="literal"><span class="pre">transform_iterator</span></tt> requirements</a></li>
<li><a class="reference" href="#transform-iterator-public-operations" id="id2" name="id2"><tt class="literal"><span class="pre">transform_iterator</span></tt> public operations</a></li>
<li><a class="reference" href="#transform-iterator-private-operations" id="id3" name="id3"><tt class="literal"><span class="pre">transform_iterator</span></tt> private operations</a></li>
</ul>
</div>
<!-- Version 1.3 of this document was accepted for TR1 -->
<pre class="literal-block">
template &lt;class UnaryFunction,
class Iterator,
class Reference = use_default,
class Value = use_default&gt;
class transform_iterator
: public iterator_adaptor&lt;/* see discussion */&gt;
{
friend class iterator_core_access;
public:
transform_iterator();
transform_iterator(Iterator const&amp; x, UnaryFunction f);
template&lt;class F2, class I2, class R2, class V2&gt;
transform_iterator(
transform_iterator&lt;F2, I2, R2, V2&gt; const&amp; t
, typename enable_if_convertible&lt;I2, Iterator&gt;::type* = 0 // exposition
, typename enable_if_convertible&lt;F2, UnaryFunction&gt;::type* = 0 // exposition
);
UnaryFunction functor() const;
private:
typename transform_iterator::value_type dereference() const;
UnaryFunction m_f;
};
</pre>
<div class="section" id="transform-iterator-requirements">
<h1><a class="toc-backref" href="#id1" name="transform-iterator-requirements"><tt class="literal"><span class="pre">transform_iterator</span></tt> requirements</a></h1>
<p>The type <tt class="literal"><span class="pre">UnaryFunction</span></tt> must be Assignable, Copy Constructible, and
the expression <tt class="literal"><span class="pre">f(*i)</span></tt> must be valid where <tt class="literal"><span class="pre">f</span></tt> is an object of
type <tt class="literal"><span class="pre">UnaryFunction</span></tt>, <tt class="literal"><span class="pre">i</span></tt> is an object of type <tt class="literal"><span class="pre">Iterator</span></tt>, and
where the type of <tt class="literal"><span class="pre">f(*i)</span></tt> must be
<tt class="literal"><span class="pre">result_of&lt;UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt>.</p>
<p>The type <tt class="literal"><span class="pre">Iterator</span></tt> must at least model Readable Iterator. The
resulting <tt class="literal"><span class="pre">transform_iterator</span></tt> models the most refined of the
following options that is also modeled by <tt class="literal"><span class="pre">Iterator</span></tt>.</p>
<blockquote>
<ul class="simple">
<li>Writable Lvalue Iterator if <tt class="literal"><span class="pre">result_of&lt;UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt> is a non-const reference.</li>
<li>Readable Lvalue Iterator if <tt class="literal"><span class="pre">result_of&lt;UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt> is a const
reference.</li>
<li>Readable Iterator otherwise.</li>
</ul>
</blockquote>
<p>The <tt class="literal"><span class="pre">transform_iterator</span></tt> models the most refined standard traversal
concept that is modeled by <tt class="literal"><span class="pre">Iterator</span></tt>.</p>
<p>The <tt class="literal"><span class="pre">reference</span></tt> type of <tt class="literal"><span class="pre">transform_iterator</span></tt> is
<tt class="literal"><span class="pre">result_of&lt;UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt>.
The <tt class="literal"><span class="pre">value_type</span></tt> is <tt class="literal"><span class="pre">remove_cv&lt;remove_reference&lt;reference&gt;</span> <span class="pre">&gt;::type</span></tt>.</p>
</div>
<div class="section" id="transform-iterator-public-operations">
<h1><a class="toc-backref" href="#id2" name="transform-iterator-public-operations"><tt class="literal"><span class="pre">transform_iterator</span></tt> public operations</a></h1>
<p><tt class="literal"><span class="pre">transform_iterator();</span></tt></p>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">transform_iterator</span></tt> with <tt class="literal"><span class="pre">m_f</span></tt>
and <tt class="literal"><span class="pre">m_iterator</span></tt> default constructed.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">transform_iterator(Iterator</span> <span class="pre">const&amp;</span> <span class="pre">x,</span> <span class="pre">UnaryFunction</span> <span class="pre">f);</span></tt></p>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">transform_iterator</span></tt> with <tt class="literal"><span class="pre">m_f</span></tt>
initialized to <tt class="literal"><span class="pre">f</span></tt> and <tt class="literal"><span class="pre">m_iterator</span></tt> initialized to <tt class="literal"><span class="pre">x</span></tt>.</td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template&lt;class OtherIterator, class R2, class V2&gt;
transform_iterator(
transform_iterator&lt;UnaryFunction, OtherIterator, R2, V2&gt; const&amp; t
, typename enable_if_convertible&lt;OtherIterator, Iterator&gt;::type* = 0 // exposition
);
</pre>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">transform_iterator</span></tt> that is a copy of <tt class="literal"><span class="pre">t</span></tt>.</td>
</tr>
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="literal"><span class="pre">OtherIterator</span></tt> is implicitly convertible to <tt class="literal"><span class="pre">Iterator</span></tt>.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">UnaryFunction</span> <span class="pre">functor()</span> <span class="pre">const;</span></tt></p>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">m_f</span></tt></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="transform-iterator-private-operations">
<h1><a class="toc-backref" href="#id3" name="transform-iterator-private-operations"><tt class="literal"><span class="pre">transform_iterator</span></tt> private operations</a></h1>
<p><tt class="literal"><span class="pre">typename</span> <span class="pre">transform_iterator::value_type</span> <span class="pre">dereference()</span> <span class="pre">const;</span></tt></p>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">m_f(transform_iterator::dereference());</span></tt></td>
</tr>
</tbody>
</table>
</div>
</div>
</body>
</html>
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