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| <title>Permutation Iterator</title> |
| <meta name="author" content="Toon Knapen, David Abrahams, Roland Richter, Jeremy Siek" /> |
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| <meta name="date" content="2006-09-11" /> |
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| <div class="document" id="permutation-iterator"> |
| <h1 class="title">Permutation 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>Toon Knapen, David Abrahams, Roland Richter, Jeremy Siek</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="last reference external" href="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</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="last reference external" href="http://www.osl.iu.edu">Open Systems |
| Lab</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 Toon Knapen, David Abrahams, Roland Richter, and Jeremy Siek 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 permutation iterator adaptor provides a permuted view of a given |
| range. That is, the view includes every element of the given range but |
| in a potentially different order.</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="#introduction" id="id2">Introduction</a></li> |
| <li><a class="reference internal" href="#reference" id="id3">Reference</a><ul> |
| <li><a class="reference internal" href="#permutation-iterator-requirements" id="id4"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> requirements</a></li> |
| <li><a class="reference internal" href="#permutation-iterator-models" id="id5"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models</a></li> |
| <li><a class="reference internal" href="#permutation-iterator-operations" id="id6"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> operations</a></li> |
| </ul> |
| </li> |
| <li><a class="reference internal" href="#example" id="id7">Example</a></li> |
| </ul> |
| </div> |
| <div class="section" id="introduction"> |
| <h1><a class="toc-backref" href="#id2">Introduction</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) --> |
| <p>The adaptor takes two arguments:</p> |
| <blockquote> |
| <ul class="simple"> |
| <li>an iterator to the range V on which the permutation |
| will be applied</li> |
| <li>the reindexing scheme that defines how the |
| elements of V will be permuted.</li> |
| </ul> |
| </blockquote> |
| <p>Note that the permutation iterator is not limited to strict |
| permutations of the given range V. The distance between begin and end |
| of the reindexing iterators is allowed to be smaller compared to the |
| size of the range V, in which case the permutation iterator only |
| provides a permutation of a subrange of V. The indexes neither need |
| to be unique. In this same context, it must be noted that the past the |
| end permutation iterator is completely defined by means of the |
| past-the-end iterator to the indices.</p> |
| </div> |
| <div class="section" id="reference"> |
| <h1><a class="toc-backref" href="#id3">Reference</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 ElementIterator |
| , class IndexIterator |
| , class ValueT = use_default |
| , class CategoryT = use_default |
| , class ReferenceT = use_default |
| , class DifferenceT = use_default > |
| class permutation_iterator |
| { |
| public: |
| permutation_iterator(); |
| explicit permutation_iterator(ElementIterator x, IndexIterator y); |
| |
| template< class OEIter, class OIIter, class V, class C, class R, class D > |
| permutation_iterator( |
| permutation_iterator<OEIter, OIIter, V, C, R, D> const& r |
| , typename enable_if_convertible<OEIter, ElementIterator>::type* = 0 |
| , typename enable_if_convertible<OIIter, IndexIterator>::type* = 0 |
| ); |
| reference operator*() const; |
| permutation_iterator& operator++(); |
| ElementIterator const& base() const; |
| private: |
| ElementIterator m_elt; // exposition only |
| IndexIterator m_order; // exposition only |
| }; |
| |
| template <class ElementIterator, class IndexIterator> |
| permutation_iterator<ElementIterator, IndexIterator> |
| make_permutation_iterator( ElementIterator e, IndexIterator i); |
| </pre> |
| <div class="section" id="permutation-iterator-requirements"> |
| <h2><a class="toc-backref" href="#id4"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> requirements</a></h2> |
| <p><tt class="docutils literal"><span class="pre">ElementIterator</span></tt> shall model Random Access Traversal Iterator. |
| <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> shall model Readable Iterator. The value type of |
| the <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> must be convertible to the difference type of |
| <tt class="docutils literal"><span class="pre">ElementIterator</span></tt>.</p> |
| </div> |
| <div class="section" id="permutation-iterator-models"> |
| <h2><a class="toc-backref" href="#id5"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models</a></h2> |
| <p><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models the same iterator traversal concepts |
| as <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> and the same iterator access concepts as |
| <tt class="docutils literal"><span class="pre">ElementIterator</span></tt>.</p> |
| <p>If <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> models Single Pass Iterator and |
| <tt class="docutils literal"><span class="pre">ElementIterator</span></tt> models Readable Iterator then |
| <tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models Input Iterator.</p> |
| <p>If <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> models Forward Traversal Iterator and |
| <tt class="docutils literal"><span class="pre">ElementIterator</span></tt> models Readable Lvalue Iterator then |
| <tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models Forward Iterator.</p> |
| <p>If <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> models Bidirectional Traversal Iterator and |
| <tt class="docutils literal"><span class="pre">ElementIterator</span></tt> models Readable Lvalue Iterator then |
| <tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models Bidirectional Iterator.</p> |
| <p>If <tt class="docutils literal"><span class="pre">IndexIterator</span></tt> models Random Access Traversal Iterator and |
| <tt class="docutils literal"><span class="pre">ElementIterator</span></tt> models Readable Lvalue Iterator then |
| <tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models Random Access Iterator.</p> |
| <p><tt class="docutils literal"><span class="pre">permutation_iterator<E1,</span> <span class="pre">X,</span> <span class="pre">V1,</span> <span class="pre">C2,</span> <span class="pre">R1,</span> <span class="pre">D1></span></tt> is interoperable |
| with <tt class="docutils literal"><span class="pre">permutation_iterator<E2,</span> <span class="pre">Y,</span> <span class="pre">V2,</span> <span class="pre">C2,</span> <span class="pre">R2,</span> <span class="pre">D2></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> and <tt class="docutils literal"><span class="pre">E1</span></tt> is convertible |
| to <tt class="docutils literal"><span class="pre">E2</span></tt>.</p> |
| </div> |
| <div class="section" id="permutation-iterator-operations"> |
| <h2><a class="toc-backref" href="#id6"><tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> operations</a></h2> |
| <p>In addition to those operations required by the concepts that |
| <tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> models, <tt class="docutils literal"><span class="pre">permutation_iterator</span></tt> provides the |
| following operations.</p> |
| <p><tt class="docutils literal"><span class="pre">permutation_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">Effects:</th><td class="field-body">Default constructs <tt class="docutils literal"><span class="pre">m_elt</span></tt> and <tt class="docutils literal"><span class="pre">m_order</span></tt>.</td> |
| </tr> |
| </tbody> |
| </table> |
| <p><tt class="docutils literal"><span class="pre">explicit</span> <span class="pre">permutation_iterator(ElementIterator</span> <span class="pre">x,</span> <span class="pre">IndexIterator</span> <span class="pre">y);</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 <tt class="docutils literal"><span class="pre">m_elt</span></tt> from <tt class="docutils literal"><span class="pre">x</span></tt> and <tt class="docutils literal"><span class="pre">m_order</span></tt> from <tt class="docutils literal"><span class="pre">y</span></tt>.</td> |
| </tr> |
| </tbody> |
| </table> |
| <pre class="literal-block"> |
| template< class OEIter, class OIIter, class V, class C, class R, class D > |
| permutation_iterator( |
| permutation_iterator<OEIter, OIIter, V, C, R, D> const& r |
| , typename enable_if_convertible<OEIter, ElementIterator>::type* = 0 |
| , typename enable_if_convertible<OIIter, IndexIterator>::type* = 0 |
| ); |
| </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">Effects:</th><td class="field-body">Constructs <tt class="docutils literal"><span class="pre">m_elt</span></tt> from <tt class="docutils literal"><span class="pre">r.m_elt</span></tt> and |
| <tt class="docutils literal"><span class="pre">m_order</span></tt> from <tt class="docutils literal"><span class="pre">y.m_order</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">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">*(m_elt</span> <span class="pre">+</span> <span class="pre">*m_order)</span></tt></td> |
| </tr> |
| </tbody> |
| </table> |
| <p><tt class="docutils literal"><span class="pre">permutation_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_order</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">ElementIterator</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_order</span></tt></td> |
| </tr> |
| </tbody> |
| </table> |
| <pre class="literal-block"> |
| template <class ElementIterator, class IndexIterator> |
| permutation_iterator<ElementIterator, IndexIterator> |
| make_permutation_iterator(ElementIterator e, IndexIterator i); |
| </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"><tt class="docutils literal"><span class="pre">permutation_iterator<ElementIterator,</span> <span class="pre">IndexIterator>(e,</span> <span class="pre">i)</span></tt></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="section" id="example"> |
| <h1><a class="toc-backref" href="#id7">Example</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"> |
| using namespace boost; |
| int i = 0; |
| |
| typedef std::vector< int > element_range_type; |
| typedef std::list< int > index_type; |
| |
| static const int element_range_size = 10; |
| static const int index_size = 4; |
| |
| element_range_type elements( element_range_size ); |
| for(element_range_type::iterator el_it = elements.begin() ; el_it != elements.end() ; ++el_it) |
| *el_it = std::distance(elements.begin(), el_it); |
| |
| index_type indices( index_size ); |
| for(index_type::iterator i_it = indices.begin() ; i_it != indices.end() ; ++i_it ) |
| *i_it = element_range_size - index_size + std::distance(indices.begin(), i_it); |
| std::reverse( indices.begin(), indices.end() ); |
| |
| typedef permutation_iterator< element_range_type::iterator, index_type::iterator > permutation_type; |
| permutation_type begin = make_permutation_iterator( elements.begin(), indices.begin() ); |
| permutation_type it = begin; |
| permutation_type end = make_permutation_iterator( elements.begin(), indices.end() ); |
| |
| std::cout << "The original range is : "; |
| std::copy( elements.begin(), elements.end(), std::ostream_iterator< int >( std::cout, " " ) ); |
| std::cout << "\n"; |
| |
| std::cout << "The reindexing scheme is : "; |
| std::copy( indices.begin(), indices.end(), std::ostream_iterator< int >( std::cout, " " ) ); |
| std::cout << "\n"; |
| |
| std::cout << "The permutated range is : "; |
| std::copy( begin, end, std::ostream_iterator< int >( std::cout, " " ) ); |
| std::cout << "\n"; |
| |
| std::cout << "Elements at even indices in the permutation : "; |
| it = begin; |
| for(i = 0; i < index_size / 2 ; ++i, it+=2 ) std::cout << *it << " "; |
| std::cout << "\n"; |
| |
| std::cout << "Permutation backwards : "; |
| it = begin + (index_size); |
| assert( it != begin ); |
| for( ; it-- != begin ; ) std::cout << *it << " "; |
| std::cout << "\n"; |
| |
| std::cout << "Iterate backward with stride 2 : "; |
| it = begin + (index_size - 1); |
| for(i = 0 ; i < index_size / 2 ; ++i, it-=2 ) std::cout << *it << " "; |
| std::cout << "\n"; |
| </pre> |
| <p>The output is:</p> |
| <pre class="literal-block"> |
| The original range is : 0 1 2 3 4 5 6 7 8 9 |
| The reindexing scheme is : 9 8 7 6 |
| The permutated range is : 9 8 7 6 |
| Elements at even indices in the permutation : 9 7 |
| Permutation backwards : 6 7 8 9 |
| Iterate backward with stride 2 : 6 8 |
| </pre> |
| <p>The source code for this example can be found <a class="reference external" href="../example/permutation_iter_example.cpp">here</a>.</p> |
| </div> |
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