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145 lines
7.2 KiB
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<?xml version="1.0" encoding="utf-8" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="generator" content="Docutils 0.3.0: http://docutils.sourceforge.net/" />
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<title>Counting Iterator</title>
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<meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" />
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<meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab, University of Hanover Institute for Transport Railway Operation and Construction" />
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<meta name="date" content="2003-08-05" />
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<meta name="copyright" content="Copyright Dave Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved" />
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<link rel="stylesheet" href="default.css" type="text/css" />
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</head>
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<body>
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<div class="document" id="counting-iterator">
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<h1 class="title">Counting Iterator</h1>
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<table class="docinfo" frame="void" rules="none">
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<col class="docinfo-name" />
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<col class="docinfo-content" />
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<tbody valign="top">
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<tr><th class="docinfo-name">Author:</th>
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<td>David Abrahams, Jeremy Siek, Thomas Witt</td></tr>
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<tr><th class="docinfo-name">Contact:</th>
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<td><a class="first reference" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="reference" href="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</a>, <a class="last reference" href="mailto:witt@ive.uni-hannover.de">witt@ive.uni-hannover.de</a></td></tr>
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<tr><th class="docinfo-name">Organization:</th>
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<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
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Lab</a>, University of Hanover <a class="last reference" href="http://www.ive.uni-hannover.de">Institute for Transport
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Railway Operation and Construction</a></td></tr>
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<tr><th class="docinfo-name">Date:</th>
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<td>2003-08-05</td></tr>
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<tr><th class="docinfo-name">Copyright:</th>
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<td>Copyright Dave Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved</td></tr>
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</tbody>
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</table>
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<table class="field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">abstract:</th><td class="field-body"></td>
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</tr>
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</tbody>
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</table>
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<p>The counting iterator adaptor implements dereference by returning a
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reference to the base object. The other operations are implemented by
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the base <tt class="literal"><span class="pre">m_iterator</span></tt>, as per the inheritance from
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<tt class="literal"><span class="pre">iterator_adaptor</span></tt>.</p>
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<div class="contents topic" id="table-of-contents">
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<p class="topic-title"><a name="table-of-contents">Table of Contents</a></p>
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<ul class="simple">
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<li><a class="reference" href="#counting-iterator-requirements" id="id1" name="id1"><tt class="literal"><span class="pre">counting_iterator</span></tt> requirements</a></li>
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<li><a class="reference" href="#counting-iterator-operations" id="id2" name="id2"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></li>
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</ul>
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</div>
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<pre class="literal-block">
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template <class Incrementable, class Category = use_default, class Difference = use_default>
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class counting_iterator
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: public iterator_adaptor<
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counting_iterator<Incrementable, Category, Difference>
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, Incrementable
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, Incrementable
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, /* see details for category */
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, Incrementable const&
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, Incrementable const*
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, /* distance = Difference or a signed integral type */>
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{
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friend class iterator_core_access;
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public:
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counting_iterator();
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counting_iterator(counting_iterator const& rhs);
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counting_iterator(Incrementable x);
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private:
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typename counting_iterator::reference dereference() const
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{
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return this->base_reference();
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}
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};
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</pre>
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<dl>
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<dt>[<em>Note:</em> implementers are encouraged to provide an implementation of</dt>
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<dd><tt class="literal"><span class="pre">distance_to</span></tt> and a <tt class="literal"><span class="pre">difference_type</span></tt> that avoids overflows in
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the cases when the <tt class="literal"><span class="pre">Incrementable</span></tt> type is a numeric type.]</dd>
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</dl>
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<div class="section" id="counting-iterator-requirements">
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<h1><a class="toc-backref" href="#id1" name="counting-iterator-requirements"><tt class="literal"><span class="pre">counting_iterator</span></tt> requirements</a></h1>
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<p>The <tt class="literal"><span class="pre">Incrementable</span></tt> type must be Default Constructible, Copy
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Constructible, and Assignable. The default distance is
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an implementation defined signed integegral type.</p>
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<p>The resulting <tt class="literal"><span class="pre">counting_iterator</span></tt> models Readable Lvalue Iterator.</p>
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<p>Furthermore, if you wish to create a counting iterator that is a Forward
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Traversal Iterator, then the following expressions must be valid:</p>
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<pre class="literal-block">
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Incrementable i, j;
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++i // pre-increment
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i == j // operator equal
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</pre>
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<p>If you wish to create a counting iterator that is a
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Bidirectional Traversal Iterator, then pre-decrement is also required:</p>
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<pre class="literal-block">
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--i
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</pre>
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<p>If you wish to create a counting iterator that is a Random Access
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Traversal Iterator, then these additional expressions are also
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required:</p>
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<pre class="literal-block">
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counting_iterator::difference_type n;
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i += n
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n = i - j
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i < j
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</pre>
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</div>
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<div class="section" id="counting-iterator-operations">
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<h1><a class="toc-backref" href="#id2" name="counting-iterator-operations"><tt class="literal"><span class="pre">counting_iterator</span></tt> operations</a></h1>
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<p><tt class="literal"><span class="pre">counting_iterator();</span></tt></p>
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<table class="field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body">A default constructed instance of <tt class="literal"><span class="pre">counting_iterator</span></tt>.</td>
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</tr>
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</tbody>
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</table>
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<p><tt class="literal"><span class="pre">counting_iterator(counting_iterator</span> <span class="pre">const&</span> <span class="pre">rhs);</span></tt></p>
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<table class="field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">counting_iterator</span></tt> that is a copy of <tt class="literal"><span class="pre">rhs</span></tt>.</td>
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</tr>
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</tbody>
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</table>
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<p><tt class="literal"><span class="pre">counting_iterator(Incrementable</span> <span class="pre">x);</span></tt></p>
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<table class="field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">Returns:</th><td class="field-body">An instance of <tt class="literal"><span class="pre">counting_iterator</span></tt> with its base
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object copy constructed from <tt class="literal"><span class="pre">x</span></tt>.</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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</body>
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</html>
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