source: trunk/yat/utility/StrideIterator.h @ 1490

Last change on this file since 1490 was 1490, checked in by Peter, 14 years ago

fixes #440

The bug was introduced in trunk after 0.4 release, so it has never
seen daylight.

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 5.1 KB
Line 
1#ifndef _theplu_yat_utility_stride_iterator_
2#define _theplu_yat_utility_stride_iterator_
3
4// $Id: StrideIterator.h 1490 2008-09-11 22:10:26Z peter $
5
6/*
7  Copyright (C) 2007 Jari Häkkinen, Peter Johansson
8  Copyright (C) 2008 Peter Johansson
9
10  This file is part of the yat library, http://dev.thep.lu.se/yat
11
12  The yat library is free software; you can redistribute it and/or
13  modify it under the terms of the GNU General Public License as
14  published by the Free Software Foundation; either version 3 of the
15  License, or (at your option) any later version.
16
17  The yat library is distributed in the hope that it will be useful,
18  but WITHOUT ANY WARRANTY; without even the implied warranty of
19  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20  General Public License for more details.
21
22  You should have received a copy of the GNU General Public License
23  along with yat. If not, see <http://www.gnu.org/licenses/>.
24*/
25
26// debug
27#include <iostream> 
28
29#include "iterator_traits.h"
30
31#include <boost/iterator/iterator_adaptor.hpp>
32
33namespace theplu {
34namespace yat {
35namespace utility {
36
37  // forward declaration
38  template<typename Iter>
39  class StrideIterator;
40
41  /**
42     Specialization for StrideIterator that calls underlying iterator.
43   */
44  template <typename Iter>
45  struct weighted_iterator_traits<StrideIterator<Iter> > {
46    /**
47       StrideIterator is weighted if underlying iterator is weighted.
48    */
49    typedef typename weighted_iterator_traits<Iter>::type type;
50  };
51
52  /**
53     Specialization for StrideIterator using iterator_traits with base()
54   */
55  template <class Iter>
56  struct iterator_traits<StrideIterator<Iter> > {
57    /**
58       data_reference same as for underlying iterator
59     */
60    typedef typename iterator_traits<Iter>::data_reference data_reference;
61
62    /**
63       weight_reference same as for underlying iterator
64     */
65    typedef typename iterator_traits<Iter>::weight_reference weight_reference;
66
67    /**
68       \return data of iterator
69    */
70    data_reference data(StrideIterator<Iter> iter) const 
71    { return iterator_traits<Iter>().data(iter.base()); }
72
73    /**
74       \return weight of iterator
75    */
76    weight_reference weight(StrideIterator<Iter> iter) const 
77    { return iterator_traits<Iter>().weight(iter.base()); }
78
79  };
80
81  /**
82     @brief Adaptor using a stride on underlying iterator
83
84     Works as underlying iterator except that all arithmetic uses the
85     stride, so e.g., ++StrideIterator returns underlying
86     _iterator+stride
87
88  */
89  template<typename Iter>
90  class StrideIterator 
91    : public boost::iterator_adaptor<StrideIterator<Iter>, Iter>
92  {
93    typedef boost::iterator_adaptor<StrideIterator<Iter>,Iter> super_t;
94
95  public:
96    /// type of underlying iterator
97    typedef Iter iterator_type;
98
99    /*
100    /// value type
101    typedef typename std::iterator_traits<Iter>::value_type value_type;
102    /// difference type
103    typedef typename std::iterator_traits<Iter>::difference_type difference_type;
104    /// reference
105    typedef typename std::iterator_traits<Iter>::reference reference;
106    /// pointer
107    typedef typename std::iterator_traits<Iter>::pointer pointer;
108    /// weighted_iterator_tag if iterator is weighted
109    typedef typename yat::utility::weighted_iterator_traits<Iter>::type w_type;
110    */
111
112    /**
113       \brief default constructor
114
115       Using default constructor of BASE iterator.
116     */
117    explicit StrideIterator(size_t stride=1)
118      : StrideIterator::iterator_adaptor_(), stride_(stride) {}
119
120    /**
121       \brief Constructor
122    */
123    explicit StrideIterator(Iter p, size_t stride=1)
124      : StrideIterator::iterator_adaptor_(p), stride_(stride) {}
125
126   
127    /**
128       \brief Copy constructor
129     */
130    StrideIterator(const StrideIterator& other)
131      : StrideIterator::iterator_adaptor_(other.base()), stride_(other.stride()) 
132    {}
133
134    /**
135       \brief Conversion constructor.
136
137       Create a StrideIterator<Iter> from a StrideIterator<I2>. Possible
138       if I2 is convertible to a Iter. Constructor allows implicit
139       conversions such as iterator to const_iterator.
140     */
141    template<typename I2>
142    StrideIterator(StrideIterator<I2> other,
143                   typename boost::enable_if_convertible<I2, Iter>::type* = 0 )
144      : StrideIterator::iterator_adaptor_(other.base()), 
145        stride_(other.stride()) {}
146
147    /**
148        \brief Assignment operator
149     */
150    StrideIterator& operator=(const StrideIterator& rhs)
151    {
152      stride_ = rhs.stride();
153      this->base_reference() = rhs.base();
154      return *this;
155    }
156
157    /**
158       \return stride
159     */
160    inline size_t stride(void) const { return stride_; }
161
162  private:
163    // to give base class access to private parts
164    friend class boost::iterator_core_access;
165   
166    size_t stride_;
167
168    //typedef typename StrideIterator::iterator_adaptor_::difference_type
169    typedef typename StrideIterator::iterator_adaptor_::difference_type
170    difference_t;
171
172    void advance(typename super_t::difference_type n)
173    { this->base_reference() += stride_*n; }
174
175    void decrement(void) { this->base_reference()-=stride_; }
176
177    template <class OtherIterator>
178    typename super_t::difference_type
179    distance_to(const StrideIterator<OtherIterator>& other) const
180    { 
181      // casting to int to avoid loss of sign in numerator
182      return (other.base() - this->base() )/static_cast<int>(stride_); 
183    }
184
185    void increment(void) { this->base_reference()+=stride_; }
186
187  };
188
189
190
191
192
193}}} // of namespace utility, yat, and theplu
194
195#endif
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