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- <title>Reverse 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="2006-09-11" />
- <meta name="copyright" content="Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003." />
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- <div class="document" id="reverse-iterator">
- <h1 class="title">Reverse 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 external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="reference external" href="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</a>, <a class="last reference external" href="mailto:witt@ive.uni-hannover.de">witt@ive.uni-hannover.de</a></td></tr>
- <tr><th class="docinfo-name">Organization:</th>
- <td><a class="first reference external" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="reference external" href="http://www.osl.iu.edu">Open Systems
- Lab</a>, University of Hanover <a class="last reference external" 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>2006-09-11</td></tr>
- <tr><th class="docinfo-name">Copyright:</th>
- <td>Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003.</td></tr>
- </tbody>
- </table>
- <!-- Distributed under the Boost -->
- <!-- Software License, Version 1.0. (See accompanying -->
- <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
- <table class="docutils field-list" frame="void" rules="none">
- <col class="field-name" />
- <col class="field-body" />
- <tbody valign="top">
- <tr class="field"><th class="field-name">abstract:</th><td class="field-body"><!-- Copyright David Abrahams 2006. Distributed under the Boost -->
- <!-- Software License, Version 1.0. (See accompanying -->
- <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
- The reverse iterator adaptor iterates through the adapted iterator
- range in the opposite direction.</td>
- </tr>
- </tbody>
- </table>
- <div class="contents topic" id="table-of-contents">
- <p class="topic-title first">Table of Contents</p>
- <ul class="simple">
- <li><a class="reference internal" href="#reverse-iterator-synopsis" id="id2"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> synopsis</a></li>
- <li><a class="reference internal" href="#reverse-iterator-requirements" id="id3"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> requirements</a></li>
- <li><a class="reference internal" href="#reverse-iterator-models" id="id4"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> models</a></li>
- <li><a class="reference internal" href="#reverse-iterator-operations" id="id5"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> operations</a></li>
- <li><a class="reference internal" href="#example" id="id6">Example</a></li>
- </ul>
- </div>
- <div class="section" id="reverse-iterator-synopsis">
- <h1><a class="toc-backref" href="#id2"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> synopsis</a></h1>
- <!-- Copyright David Abrahams 2006. Distributed under the Boost -->
- <!-- Software License, Version 1.0. (See accompanying -->
- <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
- <pre class="literal-block">
- template <class Iterator>
- class reverse_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;
- reverse_iterator() {}
- explicit reverse_iterator(Iterator x) ;
- template<class OtherIterator>
- reverse_iterator(
- reverse_iterator<OtherIterator> const& r
- , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0 // exposition
- );
- Iterator const& base() const;
- reference operator*() const;
- reverse_iterator& operator++();
- reverse_iterator& operator--();
- private:
- Iterator m_iterator; // exposition
- };
- </pre>
- <p>If <tt class="docutils literal"><span class="pre">Iterator</span></tt> models Random Access Traversal Iterator and Readable
- Lvalue Iterator, then <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible to
- <tt class="docutils literal"><span class="pre">random_access_iterator_tag</span></tt>. Otherwise, if
- <tt class="docutils literal"><span class="pre">Iterator</span></tt> models Bidirectional Traversal Iterator and Readable
- Lvalue Iterator, then <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible to
- <tt class="docutils literal"><span class="pre">bidirectional_iterator_tag</span></tt>. Otherwise, <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is
- convertible to <tt class="docutils literal"><span class="pre">input_iterator_tag</span></tt>.</p>
- </div>
- <div class="section" id="reverse-iterator-requirements">
- <h1><a class="toc-backref" href="#id3"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> requirements</a></h1>
- <p><tt class="docutils literal"><span class="pre">Iterator</span></tt> must be a model of Bidirectional Traversal Iterator. The
- type <tt class="docutils literal"><span class="pre">iterator_traits<Iterator>::reference</span></tt> must be the type of
- <tt class="docutils literal"><span class="pre">*i</span></tt>, where <tt class="docutils literal"><span class="pre">i</span></tt> is an object of type <tt class="docutils literal"><span class="pre">Iterator</span></tt>.</p>
- </div>
- <div class="section" id="reverse-iterator-models">
- <h1><a class="toc-backref" href="#id4"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> models</a></h1>
- <p>A specialization of <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> models the same iterator
- traversal and iterator access concepts modeled by its <tt class="docutils literal"><span class="pre">Iterator</span></tt>
- argument. In addition, it may model old iterator concepts
- specified in the following table:</p>
- <table border="1" class="docutils">
- <colgroup>
- <col width="53%" />
- <col width="47%" />
- </colgroup>
- <thead valign="bottom">
- <tr><th class="head">If <tt class="docutils literal"><span class="pre">I</span></tt> models</th>
- <th class="head">then <tt class="docutils literal"><span class="pre">reverse_iterator<I></span></tt> models</th>
- </tr>
- </thead>
- <tbody valign="top">
- <tr><td>Readable Lvalue Iterator,
- Bidirectional Traversal Iterator</td>
- <td>Bidirectional Iterator</td>
- </tr>
- <tr><td>Writable Lvalue Iterator,
- Bidirectional Traversal Iterator</td>
- <td>Mutable Bidirectional Iterator</td>
- </tr>
- <tr><td>Readable Lvalue Iterator,
- Random Access Traversal Iterator</td>
- <td>Random Access Iterator</td>
- </tr>
- <tr><td>Writable Lvalue Iterator,
- Random Access Traversal Iterator</td>
- <td>Mutable Random Access Iterator</td>
- </tr>
- </tbody>
- </table>
- <p><tt class="docutils literal"><span class="pre">reverse_iterator<X></span></tt> is interoperable with
- <tt class="docutils literal"><span class="pre">reverse_iterator<Y></span></tt> if and only if <tt class="docutils literal"><span class="pre">X</span></tt> is interoperable with
- <tt class="docutils literal"><span class="pre">Y</span></tt>.</p>
- </div>
- <div class="section" id="reverse-iterator-operations">
- <h1><a class="toc-backref" href="#id5"><tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> operations</a></h1>
- <p>In addition to the operations required by the concepts modeled by
- <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt>, <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> provides the following
- operations.</p>
- <p><tt class="docutils literal"><span class="pre">reverse_iterator();</span></tt></p>
- <table class="docutils 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="docutils literal"><span class="pre">Iterator</span></tt> must be Default Constructible.</td>
- </tr>
- <tr class="field"><th class="field-name">Effects:</th><td class="field-body">Constructs an instance of <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> with <tt class="docutils literal"><span class="pre">m_iterator</span></tt>
- default constructed.</td>
- </tr>
- </tbody>
- </table>
- <p><tt class="docutils literal"><span class="pre">explicit</span> <span class="pre">reverse_iterator(Iterator</span> <span class="pre">x);</span></tt></p>
- <table class="docutils 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">Constructs an instance of <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> with
- <tt class="docutils literal"><span class="pre">m_iterator</span></tt> copy constructed from <tt class="docutils literal"><span class="pre">x</span></tt>.</td>
- </tr>
- </tbody>
- </table>
- <pre class="literal-block">
- template<class OtherIterator>
- reverse_iterator(
- reverse_iterator<OtherIterator> const& r
- , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0 // exposition
- );
- </pre>
- <table class="docutils 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="docutils literal"><span class="pre">OtherIterator</span></tt> is implicitly convertible to <tt class="docutils literal"><span class="pre">Iterator</span></tt>.</td>
- </tr>
- <tr class="field"><th class="field-name">Effects:</th><td class="field-body">Constructs instance of <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt> whose
- <tt class="docutils literal"><span class="pre">m_iterator</span></tt> subobject is constructed from <tt class="docutils literal"><span class="pre">y.base()</span></tt>.</td>
- </tr>
- </tbody>
- </table>
- <p><tt class="docutils literal"><span class="pre">Iterator</span> <span class="pre">const&</span> <span class="pre">base()</span> <span class="pre">const;</span></tt></p>
- <table class="docutils 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="docutils literal"><span class="pre">m_iterator</span></tt></td>
- </tr>
- </tbody>
- </table>
- <p><tt class="docutils literal"><span class="pre">reference</span> <span class="pre">operator*()</span> <span class="pre">const;</span></tt></p>
- <table class="docutils 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"></td>
- </tr>
- </tbody>
- </table>
- <pre class="literal-block">
- Iterator tmp = m_iterator;
- return *--tmp;
- </pre>
- <p><tt class="docutils literal"><span class="pre">reverse_iterator&</span> <span class="pre">operator++();</span></tt></p>
- <table class="docutils 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"><tt class="docutils literal"><span class="pre">--m_iterator</span></tt></td>
- </tr>
- <tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
- </tr>
- </tbody>
- </table>
- <p><tt class="docutils literal"><span class="pre">reverse_iterator&</span> <span class="pre">operator--();</span></tt></p>
- <table class="docutils 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"><tt class="docutils literal"><span class="pre">++m_iterator</span></tt></td>
- </tr>
- <tr class="field"><th class="field-name">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*this</span></tt></td>
- </tr>
- </tbody>
- </table>
- <!-- Copyright David Abrahams 2006. Distributed under the Boost -->
- <!-- Software License, Version 1.0. (See accompanying -->
- <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
- <pre class="literal-block">
- template <class BidirectionalIterator>
- reverse_iterator<BidirectionalIterator>n
- make_reverse_iterator(BidirectionalIterator x);
- </pre>
- <table class="docutils 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="docutils literal"><span class="pre">reverse_iterator<BidirectionalIterator></span></tt>
- with a <tt class="docutils literal"><span class="pre">current</span></tt> constructed from <tt class="docutils literal"><span class="pre">x</span></tt>.</td>
- </tr>
- </tbody>
- </table>
- <!-- Copyright David Abrahams 2006. Distributed under the Boost -->
- <!-- Software License, Version 1.0. (See accompanying -->
- <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
- </div>
- <div class="section" id="example">
- <h1><a class="toc-backref" href="#id6">Example</a></h1>
- <p>The following example prints an array of characters in reverse order
- using <tt class="docutils literal"><span class="pre">reverse_iterator</span></tt>.</p>
- <pre class="literal-block">
- char letters_[] = "hello world!";
- const int N = sizeof(letters_)/sizeof(char) - 1;
- typedef char* base_iterator;
- base_iterator letters(letters_);
- std::cout << "original sequence of letters:\t\t\t" << letters_ << std::endl;
- boost::reverse_iterator<base_iterator>
- reverse_letters_first(letters + N),
- reverse_letters_last(letters);
- std::cout << "sequence in reverse order:\t\t\t";
- std::copy(reverse_letters_first, reverse_letters_last,
- std::ostream_iterator<char>(std::cout));
- std::cout << std::endl;
- std::cout << "sequence in double-reversed (normal) order:\t";
- std::copy(boost::make_reverse_iterator(reverse_letters_last),
- boost::make_reverse_iterator(reverse_letters_first),
- std::ostream_iterator<char>(std::cout));
- std::cout << std::endl;
- </pre>
- <p>The output is:</p>
- <pre class="literal-block">
- original sequence of letters: hello world!
- sequence in reverse order: !dlrow olleh
- sequence in double-reversed (normal) order: hello world!
- </pre>
- <p>The source code for this example can be found <a class="reference external" href="../example/reverse_iterator_example.cpp">here</a>.</p>
- </div>
- </div>
- <div class="footer">
- <hr class="footer" />
- <a class="reference external" href="reverse_iterator.rst">View document source</a>.
- Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
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