mirror of
https://github.com/boostorg/iterator.git
synced 2025-05-11 13:33:56 +00:00
216 lines
11 KiB
HTML
216 lines
11 KiB
HTML
<?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">
|
|
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="generator" content="Docutils 0.3.0: http://docutils.sourceforge.net/" />
|
|
<title>Permutation Iterator</title>
|
|
<meta name="author" content="Toon Knapen, David Abrahams, Roland Richter, Jeremy Siek" />
|
|
<meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab" />
|
|
<meta name="date" content="2004-01-12" />
|
|
<meta name="copyright" content="Copyright Toon Knapen, David Abrahams, Roland Richter, and Jeremy Siek 2003. All rights reserved" />
|
|
<link rel="stylesheet" href="default.css" type="text/css" />
|
|
</head>
|
|
<body>
|
|
<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" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="last reference" 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" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="last reference" href="http://www.osl.iu.edu">Open Systems
|
|
Lab</a></td></tr>
|
|
<tr><th class="docinfo-name">Date:</th>
|
|
<td>2004-01-12</td></tr>
|
|
<tr><th class="docinfo-name">Copyright:</th>
|
|
<td>Copyright Toon Knapen, David Abrahams, Roland Richter, and Jeremy Siek 2003. All rights reserved</td></tr>
|
|
</tbody>
|
|
</table>
|
|
<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">abstract:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>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.</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="#introduction" id="id4" name="id4">Introduction</a></li>
|
|
<li><a class="reference" href="#reference" id="id5" name="id5">Reference</a><ul>
|
|
<li><a class="reference" href="#permutation-iterator-requirements" id="id6" name="id6"><tt class="literal"><span class="pre">permutation_iterator</span></tt> requirements</a></li>
|
|
<li><a class="reference" href="#permutation-iterator-operations" id="id7" name="id7"><tt class="literal"><span class="pre">permutation_iterator</span></tt> operations</a></li>
|
|
</ul>
|
|
</li>
|
|
<li><a class="reference" href="#example" id="id8" name="id8">Example</a></li>
|
|
</ul>
|
|
</div>
|
|
<div class="section" id="introduction">
|
|
<h1><a class="toc-backref" href="#id4" name="introduction">Introduction</a></h1>
|
|
<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="#id5" name="reference">Reference</a></h1>
|
|
<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
|
|
);
|
|
ElementIterator base() const;
|
|
private:
|
|
ElementIterator m_iterator; // exposition
|
|
};
|
|
|
|
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="#id6" name="permutation-iterator-requirements"><tt class="literal"><span class="pre">permutation_iterator</span></tt> requirements</a></h2>
|
|
<p><tt class="literal"><span class="pre">ElementIterator</span></tt> must be a model of <a class="reference" href="http://www.sgi.com/tech/stl/RandomAccessIterator.html">RandomAccessIterator</a>.
|
|
<tt class="literal"><span class="pre">IndexIterator</span></tt> must at least be a model <a class="reference" href="http://www.sgi.com/tech/stl/ForwardIterator.html">ForwardIterator</a>. The
|
|
value type of the <tt class="literal"><span class="pre">IndexIterator</span></tt> must be convertible to the
|
|
difference type of <tt class="literal"><span class="pre">ElementIterator</span></tt>.</p>
|
|
</div>
|
|
<div class="section" id="permutation-iterator-operations">
|
|
<h2><a class="toc-backref" href="#id7" name="permutation-iterator-operations"><tt class="literal"><span class="pre">permutation_iterator</span></tt> operations</a></h2>
|
|
<p>The permutation iterator implements the member functions and operators
|
|
required for the <a class="reference" href="http://www.sgi.com/tech/stl/RandomAccessIterator.html">Random Access Iterator</a> concept. However, the
|
|
permutation iterator can only meet the complexity guarantees of the
|
|
same concept as the IndexIterator. Thus for instance, although the
|
|
permutation iterator provides <tt class="literal"><span class="pre">operator+=(distance)</span></tt>, this operation
|
|
will take linear time in case the IndexIterator is a model of
|
|
ForwardIterator instead of amortized constant time.</p>
|
|
<pre class="literal-block">
|
|
template <class ElementIterator, class IndexIterator>
|
|
permutation_iterator<ElementIterator, IndexIterator>
|
|
make_permutation_iterator(ElementIterator e, IndexIterator i);
|
|
</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">permutation_iterator<ElementIterator,</span> <span class="pre">IndexIterator></span></tt>
|
|
that views the range of elements starting at <tt class="literal"><span class="pre">e`</span> <span class="pre">in</span> <span class="pre">the</span> <span class="pre">order</span> <span class="pre">given</span>
|
|
<span class="pre">by</span> <span class="pre">``i</span></tt>.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p><tt class="literal"><span class="pre">ElementIterator</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>
|
|
</div>
|
|
</div>
|
|
<div class="section" id="example">
|
|
<h1><a class="toc-backref" href="#id8" name="example">Example</a></h1>
|
|
<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>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|