source: trunk/yat/utility/iterator_traits.h @ 1541

Last change on this file since 1541 was 1541, checked in by Peter, 13 years ago

fixes #445 so iterator_traits detects when value_type is DataWeight?
and return weighted_iterator_tag. Also weighted_iterator_traits
recognize some normal cases; when reference_type is DataWeight?& or
const DataWeight?& weighted behaviour is performed.

Fixed some incorrect inclusion in WeightedIterator? and removed debug
code in StrideIterator?.

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 7.9 KB
Line 
1#ifndef _theplu_yat_utility_iterator_traits_
2#define _theplu_yat_utility_iterator_traits_
3
4// $Id: iterator_traits.h 1541 2008-09-30 17:40:41Z peter $
5
6/*
7  Copyright (C) 2007 Jari Häkkinen, Peter Johansson
8  Copyright (C) 2008 Peter Johansson, Markus Ringnér
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#include "DataWeight.h"
27
28#include <iterator>
29
30namespace theplu {
31namespace yat {
32namespace utility {
33
34  /**
35    Struct to be used to make compile-time decision that Iterator is
36    unweighted, which is the default.
37   */ 
38  struct unweighted_iterator_tag {};
39   
40  /**
41    Struct to be used to make compile-time decision that Iterator is
42    weighted. Some algorithms come also in a weighted version and
43    this tag could be used to decide on using them (rather than
44    the corresponding unweighted algorithm).
45   */ 
46  struct weighted_iterator_tag {};
47
48
49  /**
50     \internal
51
52     used in weighted_iterator_traits
53  */
54  template <typename T>
55  struct weighted_iterator_traits_detail {
56    /**
57       default is a iterator unweighted
58    */
59    typedef unweighted_iterator_tag type;
60  }; 
61
62  /**
63      \internal
64
65      specialization for iterators with value type DataWeight
66  */
67  template <>
68  struct weighted_iterator_traits_detail<DataWeight> {
69    /**
70       Iterators with value type DataWeight is weighted
71     */
72    typedef weighted_iterator_tag type;
73  }; 
74
75  /**
76      Metafunction to decide whether an iterator is weighted or
77      non-weighted. This (default) implementation return unweighted,
78      unless value_type of iterator is DataWeight in which case
79      weighted is returned.
80  */
81  template <class T>
82  struct weighted_iterator_traits
83  {
84  private:
85    typedef typename std::iterator_traits<T>::value_type value;
86  public:
87    /**
88       \return weighted if value_type is DataWeight
89     */
90    typedef typename weighted_iterator_traits_detail<value>::type type;
91  };
92
93
94  /**
95     \internal
96
97    Metafunction that works on a pair weighted-unweighted types and
98    return weighted_type. The metafunction is specialized for
99    unweighted unweighted in which case unweighted is returned.
100   */
101  template <class T1, class T2>
102  struct unweighted_type_and {
103    /**
104       default return weighted_iterator_tag
105     */
106    typedef weighted_iterator_tag type;
107  };
108
109  /**
110     \internal
111
112    Specialization that sets type to be unweighted when both arguments
113    are unweighted
114   */
115  template <>
116  struct unweighted_type_and<unweighted_iterator_tag, unweighted_iterator_tag> {
117    /**
118       return unweighted_iterator_tag
119     */
120    typedef unweighted_iterator_tag type;
121  };
122
123  /**
124    struct used to determine if a pair of iterators should be treated
125    as weighted. If both iterators are unweighted, type is set to
126    unweighted else weighted.
127  */
128  template <class T1, class T2>
129  struct weighted_if_any2 {
130  private:
131    typedef typename weighted_iterator_traits<T1>::type w_type1;
132    typedef typename weighted_iterator_traits<T2>::type w_type2;
133  public:
134    /// return unweighted if both are unweighted
135    typedef typename unweighted_type_and<w_type1, w_type2>::type type;
136  };
137
138  /**
139    Same as weighted_iterator_traits2 but for 3 arguments.
140   */
141  template <class T1, class T2, class T3>
142  struct weighted_if_any3 {
143  private:
144    typedef typename weighted_if_any2<T1, T2>::type tmp;
145    typedef typename weighted_iterator_traits<T3>::type w_type3;
146  public:
147    /// return unweighted if all are unweighted
148    typedef typename unweighted_type_and<tmp, w_type3>::type type;
149  };
150
151  /// check (at compile time) that iterator is unweighted.
152  inline void check_iterator_is_unweighted(unweighted_iterator_tag x){} 
153
154  /**
155     check (at compile time) that iterator \a iter is unweighted. This
156     function is strictly not needed, but exists only for convenience.
157   */
158  template <class Iter>
159  void check_iterator_is_unweighted(Iter iter) 
160  { check_iterator_is_unweighted(typename 
161                                 weighted_iterator_traits<Iter>::type());
162  }
163
164
165  /**
166     \internal
167
168     This class is used in iterator_traits to separate different cases.
169
170     This the default implementation that could be used for unweighted
171     iterators.
172   */
173  template <typename Iter, typename T >
174  struct iterator_traits_detail
175  {
176    /**
177       for unweighted data_reference is reference
178    */
179    typedef typename std::iterator_traits<Iter>::reference data_reference;
180
181    /**
182       for unweighted weight_reference is a double
183    */
184    typedef double weight_reference;
185
186    /**
187       Constructor just checking that iterator is unweighted
188    */
189    iterator_traits_detail(void) 
190    { check_iterator_is_unweighted(typename 
191                                   weighted_iterator_traits<Iter>::type());
192    }
193   
194    /**
195       \return * \a iter
196    */
197    data_reference data(Iter iter) const { return *iter; }
198
199    /**
200       \return 1.0
201    */
202    weight_reference weight(Iter iter) const { return 1.0; }
203  };
204
205
206  /**
207     specialization for weighted iterator with reference DataWeight&
208   */
209  template <typename Iter>
210  struct iterator_traits_detail<Iter, DataWeight&> {
211    /**
212       for mutable weighted iterator data_reference is double&
213    */
214    typedef double& data_reference;
215
216    /**
217       for mutable weighted iterator weight_reference is double&
218    */
219    typedef double& weight_reference;
220
221    /**
222       \return reference to data of iterator
223    */
224    data_reference data(Iter iter) const { return iter->data(); }
225
226    /**
227       \return reference to weight of iterator
228    */
229    weight_reference weight(Iter iter) const { return iter->weight(); }
230  };
231
232
233  /**
234     specialization for weighted iterator with reference const DataWeight&
235   */
236  template <typename Iter>
237  struct iterator_traits_detail<Iter, const DataWeight&> {
238    /**
239       for read-only weighted iterator data_reference is const double&
240    */
241    typedef const double& data_reference;
242
243    /**
244       for read-only weighted iterator data_reference is const double&
245    */
246    typedef const double& weight_reference;
247
248    /**
249       \return const reference to data of iterator
250    */
251    data_reference data(Iter iter) const { return iter->data(); }
252
253    /**
254       \return const reference to weight of iterator
255    */
256    weight_reference weight(Iter iter) const { return iter->weight(); }
257  };
258
259
260  /**
261     The purpose of this class is to allow polymorphism between
262     weighted and unweighted iterators. It allows to access data and
263     weight for both weighted and unweighted iterators.
264
265     This class works for unweighted iterators as well as weighted
266     iterators as long as they have reference type DataWeight& or
267     const DataWeight&.
268
269     For others, such as WeightedIterator for which reference type is
270     a proxy class, this class should be specialized. For adaptors
271     that have an underlying iterator (e.g. StrideIterator), this
272     class should be specialized, so the class also works when the
273     underlying is an iterator that is not overed by this class
274     e.g. WeightedIterator.
275   */ 
276  template <typename Iter>
277  struct iterator_traits {
278  private:
279    typedef typename std::iterator_traits<Iter>::reference reference;
280    typedef iterator_traits_detail<Iter, reference> traits;
281  public:
282    /**
283       data_reference (type returned by data(void) is determined by
284       iterator_traits_detail
285     */
286    typedef typename traits::data_reference data_reference;
287
288    /**
289       data_reference (type returned by data(void) is determined by
290       iterator_traits_detail
291     */
292    typedef typename traits::weight_reference weight_reference;
293
294    /**
295       \return data
296    */
297    data_reference data(Iter iter) const 
298    { return traits().data(iter); }
299
300    /**
301       \return
302     */
303    weight_reference weight(Iter iter) const 
304    { return traits().weight(iter); }
305
306  };
307
308
309}}} // of namespace utility, yat, and theplu
310
311#endif
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