source: trunk/yat/utility/iterator_traits.h @ 1041

Last change on this file since 1041 was 1041, checked in by Peter, 13 years ago

generalized StrideIterator? to work with Iterators as well - not only pointers

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1#ifndef _theplu_yat_utility_iterator_traits_
2#define _theplu_yat_utility_iterator_traits_
3
4// $Id: iterator_traits.h 1041 2008-02-06 17:36:54Z peter $
5
6/*
7  Copyright (C) 2007 Peter Johansson
8
9  This file is part of the yat library, http://trac.thep.lu.se/yat
10
11  The yat library is free software; you can redistribute it and/or
12  modify it under the terms of the GNU General Public License as
13  published by the Free Software Foundation; either version 2 of the
14  License, or (at your option) any later version.
15
16  The yat library is distributed in the hope that it will be useful,
17  but WITHOUT ANY WARRANTY; without even the implied warranty of
18  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19  General Public License for more details.
20
21  You should have received a copy of the GNU General Public License
22  along with this program; if not, write to the Free Software
23  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
24  02111-1307, USA.
25*/
26
27#include "IteratorWeighted.h"
28
29namespace theplu {
30namespace yat {
31namespace utility {
32
33  /**
34    Struct to be used to make compile-time decision that Iterator is
35    unweighted, which is the default.
36   */ 
37  struct unweighted_type {
38    typedef unweighted_type type;
39  };
40   
41  /**
42    Struct to be used to make compile-time decision that Iterator is
43    weighted. Some algorithms come in also in a weighted version in
44    this tag could be used to decide on using them (rather than
45    unweighted cousin).
46   */ 
47  struct weighted_type {
48    typedef weighted_type type;
49  };
50
51  /// All iterators should default to unweighted type ...
52  template <class T>
53  struct weighted_iterator_traits {
54    typedef unweighted_type type;
55  };
56
57  /// but specialized to return weighted type for some things
58  //
59  // if you add a new weighted iterator, add a new specialization like
60  // this one.
61  template <class U, class V>
62  struct weighted_iterator_traits<yat::utility::IteratorWeighted<U,V> > {
63    typedef weighted_type type;
64  };
65
66  /**
67    Metafunction that works on a pair weighted-unweighted types and
68    return weighted_type. The metafunction is specialized for
69    unweighted unweighted in which case unweighted is returned.
70   */
71  template <class T1, class T2>
72  struct unweighted_type_and {
73    typedef weighted_type type;
74  };
75
76  /**
77    Specialization that sets type to be unweighted when both arguments
78    are unweighted
79   */
80  template <>
81  struct unweighted_type_and<unweighted_type, unweighted_type> {
82    typedef unweighted_type type;
83  };
84
85  /**
86    struct used to determine if a pair of iterators should be treated
87    as weighted. If both iterators are unweighted, type is set to
88    unweighted else weighted.
89  */
90  template <class T1, class T2>
91  struct weighted_if_any2 {
92    typedef typename weighted_iterator_traits<T1>::type w_type1;
93    typedef typename weighted_iterator_traits<T2>::type w_type2;
94    typedef typename unweighted_type_and<w_type1, w_type2>::type type;
95  };
96
97  /**
98    Same as weighted_iterator_traits2 but for 3 arguments.
99   */
100  template <class T1, class T2, class T3>
101  struct weighted_if_any3 {
102    typedef typename weighted_if_any2<T1, T2>::type tmp;
103    typedef typename weighted_iterator_traits<T3>::type w_type3;
104    typedef typename unweighted_type_and<tmp, w_type3>::type type;
105  };
106
107  /// check (at compile time) that iterator is unweighted.
108  inline void check_iterator_is_unweighted(unweighted_type x){} 
109
110  /**
111     check (at compile time) that iterator \a iter is unweighted. This
112     function is strictly not needed, but exists only for convenience.
113   */
114  template <class Iter>
115  void check_iterator_is_unweighted(Iter iter) 
116  { check_iterator_is_unweighted(typename 
117                                 weighted_iterator_traits<Iter>::type());
118  }
119
120
121  /**
122    Function to be used to make compile-time decision how to return
123    data from an iterator separating two cases: weighted and
124    unweighted.
125
126    In this way unweighted iterators can be used in a weighted context.
127   */ 
128  // Peter, perhaps these should be templatized, but for now return
129  // type double is hard coded.
130  template <class Iter>
131  double iterator_traits_data(Iter iter)
132  { return iterator_traits_data(iter, typename 
133                                weighted_iterator_traits<Iter>::type()); } 
134
135  /**
136     \return data for weighted iterator
137   */
138  template <class Iter>
139  double iterator_traits_data(Iter i, weighted_type)
140  { return i.data(); } 
141
142  /**
143     \return data for unweighted data
144   */
145  template <class Iter>
146  double iterator_traits_data(Iter i, unweighted_type)
147  { return *i; } 
148
149  /**
150    Function to be used to make compile-time decision how to return
151    data from an iterator separating two cases: weighted and
152    unweighted.
153
154    In this way unweighted iterators can be used in a weighted context
155    and weight will be set to unity.
156   */ 
157  // Peter, perhaps these should be templatized, but for now return
158  // type double is hard coded.
159  template <class Iter>
160  double iterator_traits_weight(Iter iter)
161  { return iterator_traits_weight(iter, typename 
162                                  weighted_iterator_traits<Iter>::type()); } 
163
164  /**
165     \return weight for weighted iterator
166   */
167  template <class Iter>
168  double iterator_traits_weight(Iter i, weighted_type)
169  { return i.weight(); } 
170
171  /**
172     \return weight for unweighted iterator
173   */
174  template <class Iter>
175  double iterator_traits_weight(Iter i, unweighted_type)
176  { return 1.0; } 
177
178
179}}} // of namespace utility, yat, and theplu
180
181#endif
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