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<pre class="literal-block">
template <class Predicate, class Iterator>
class filter_iterator
{
public:
typedef iterator_traits<Iterator>::value_type value_type;
typedef iterator_traits<Iterator>::reference reference;
typedef iterator_traits<Iterator>::pointer pointer;
typedef iterator_traits<Iterator>::difference_type difference_type;
typedef /* see below */ iterator_category;
filter_iterator();
filter_iterator(Predicate f, Iterator x, Iterator end = Iterator());
filter_iterator(Iterator x, Iterator end = Iterator());
template<class OtherIterator>
filter_iterator(
filter_iterator<Predicate, OtherIterator> const& t
, typename enable_if_convertible<OtherIterator, Iterator>::type* = 0 // exposition
);
Predicate predicate() const;
Iterator end() const;
Iterator base() const;
reference operator*() const;
filter_iterator& operator++();
private:
Predicate m_pred; // exposition
Iterator m_iter; // exposition
Iterator m_end; // exposition
};
</pre>
<p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member is a type convertible to the tags
corresponding to each standard concept modeled by <tt class="literal"><span class="pre">filter_iterator</span></tt>,
as described in the models section.</p>
<div class="section" id="filter-iterator-requirements">
<h1><a name="filter-iterator-requirements"><tt class="literal"><span class="pre">filter_iterator</span></tt> requirements</a></h1>
<p>The <tt class="literal"><span class="pre">Predicate</span></tt> argument must be Assignable, Copy Constructible, and
the expression <tt class="literal"><span class="pre">p(x)</span></tt> must be valid where <tt class="literal"><span class="pre">p</span></tt> is an object of type
<tt class="literal"><span class="pre">Predicate</span></tt>, <tt class="literal"><span class="pre">x</span></tt> is an object of type
<tt class="literal"><span class="pre">iterator_traits<Iterator>::value_type</span></tt>, and where the type of
<tt class="literal"><span class="pre">p(x)</span></tt> must be convertible to <tt class="literal"><span class="pre">bool</span></tt>.</p>
<p>The <tt class="literal"><span class="pre">Iterator</span></tt> argument shall meet the requirements of Readable
Iterator and Single Pass Iterator or it shall meet the requirements of
Input Iterator.</p>
</div>
<div class="section" id="filter-iterator-models">
<h1><a name="filter-iterator-models"><tt class="literal"><span class="pre">filter_iterator</span></tt> models</a></h1>
<p>The concepts that <tt class="literal"><span class="pre">filter_iterator</span></tt> models are dependent on which
concepts the <tt class="literal"><span class="pre">Iterator</span></tt> argument models, as specified in the
following tables.</p>
<table class="table" frame="border" rules="all">
<colgroup>
<col width="33%" />
<col width="67%" />
</colgroup>
<thead valign="bottom">
<tr><th>If <tt class="literal"><span class="pre">Iterator</span></tt> models</th>
<th>then <tt class="literal"><span class="pre">filter_iterator</span></tt> models</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>Single Pass Iterator</td>
<td>Single Pass Iterator</td>
</tr>
<tr><td>Forward Traversal Iterator</td>
<td>Forward Traversal Iterator</td>
</tr>
</tbody>
</table>
<table class="table" frame="border" rules="all">
<colgroup>
<col width="41%" />
<col width="59%" />
</colgroup>
<thead valign="bottom">
<tr><th>If <tt class="literal"><span class="pre">Iterator</span></tt> models</th>
<th>then <tt class="literal"><span class="pre">filter_iterator</span></tt> models</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>Readable Iterator</td>
<td>Readable Iterator</td>
</tr>
<tr><td>Writable Iterator</td>
<td>Writable Iterator</td>
</tr>
<tr><td>Lvalue Iterator</td>
<td>Lvalue Iterator</td>
</tr>
</tbody>
</table>
<table class="table" frame="border" rules="all">
<colgroup>
<col width="63%" />
<col width="38%" />
</colgroup>
<thead valign="bottom">
<tr><th>If <tt class="literal"><span class="pre">Iterator</span></tt> models</th>
<th>then <tt class="literal"><span class="pre">filter_iterator</span></tt> models</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>Readable Iterator, Single Pass Iterator</td>
<td>Input Iterator</td>
</tr>
<tr><td>Readable Lvalue Iterator, Forward Traversal Iterator</td>
<td>Forward Iterator</td>
</tr>
<tr><td>Writable Lvalue Iterator, Forward Traversal Iterator</td>
<td>Mutable Forward Iterator</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="filter-iterator-operations">
<h1><a name="filter-iterator-operations"><tt class="literal"><span class="pre">filter_iterator</span></tt> operations</a></h1>
<p>In addition to those operations required by the concepts that
<tt class="literal"><span class="pre">filter_iterator</span></tt> models, <tt class="literal"><span class="pre">filter_iterator</span></tt> provides the following
operations.</p>
<p><tt class="literal"><span class="pre">filter_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">Requires:</th><td class="field-body"><tt class="literal"><span class="pre">Predicate</span></tt> and <tt class="literal"><span class="pre">Iterator</span></tt> must be Default Constructible.</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a <tt class="literal"><span class="pre">filter_iterator</span></tt> whose``m_pred``, <tt class="literal"><span class="pre">m_iter</span></tt>, and <tt class="literal"><span class="pre">m_end</span></tt>
members are a default constructed.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">filter_iterator(Predicate</span> <span class="pre">f,</span> <span class="pre">Iterator</span> <span class="pre">x,</span> <span class="pre">Iterator</span> <span class="pre">end</span> <span class="pre">=</span> <span class="pre">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">A <tt class="literal"><span class="pre">filter_iterator</span></tt> where <tt class="literal"><span class="pre">m_iter</span></tt> is either
the first position in the range <tt class="literal"><span class="pre">[x,end)</span></tt> such that <tt class="literal"><span class="pre">f(*m_iter)</span> <span class="pre">==</span> <span class="pre">true</span></tt>
or else``m_iter == end``. The member <tt class="literal"><span class="pre">m_pred</span></tt> is constructed from
<tt class="literal"><span class="pre">f</span></tt> and <tt class="literal"><span class="pre">m_end</span></tt> from <tt class="literal"><span class="pre">end</span></tt>.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">filter_iterator(Iterator</span> <span class="pre">x,</span> <span class="pre">Iterator</span> <span class="pre">end</span> <span class="pre">=</span> <span class="pre">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">Requires:</th><td class="field-body"><tt class="literal"><span class="pre">Predicate</span></tt> must be Default Constructible.</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">A <tt class="literal"><span class="pre">filter_iterator</span></tt> where <tt class="literal"><span class="pre">m_iter</span></tt> is either
the first position in the range <tt class="literal"><span class="pre">[x,end)</span></tt> such that <tt class="literal"><span class="pre">m_pred(*m_iter)</span> <span class="pre">==</span> <span class="pre">true</span></tt>
or else``m_iter == end``. The member <tt class="literal"><span class="pre">m_pred</span></tt> is default constructed.</td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class OtherIterator>
filter_iterator(
filter_iterator<Predicate, OtherIterator> const& t
, typename enable_if_convertible<OtherIterator, Iterator>::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">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>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">A filter iterator whose members are copied from <tt class="literal"><span class="pre">t</span></tt>.</td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">Predicate</span> <span class="pre">predicate()</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_pred</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">Iterator</span> <span class="pre">end()</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_end</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">Iterator</span> <span class="pre">base()</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_iterator</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">reference</span> <span class="pre">operator*()</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_iter</span></tt></td>
</tr>
</tbody>
</table>
<p><tt class="literal"><span class="pre">filter_iterator&</span> <span class="pre">operator++();</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">Effects:</th><td class="field-body">Increments <tt class="literal"><span class="pre">m_iter</span></tt> and then continues to
increment <tt class="literal"><span class="pre">m_iter</span></tt> until either <tt class="literal"><span class="pre">m_iter</span> <span class="pre">==</span> <span class="pre">m_end</span></tt>
or <tt class="literal"><span class="pre">m_pred(*m_iter)</span> <span class="pre">==</span> <span class="pre">true</span></tt>.</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="literal"><span class="pre">*this</span></tt></td>
</tr>
</tbody>
</table>
</div>
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