source: trunk/yat/utility/iterator_traits.h @ 1089

Last change on this file since 1089 was 1089, checked in by Peter, 13 years ago

removing IteartorWeighted?

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 3.9 KB
Line 
1#ifndef _theplu_yat_utility_iterator_traits_
2#define _theplu_yat_utility_iterator_traits_
3
4// $Id: iterator_traits.h 1089 2008-02-14 14:37:12Z 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
27namespace theplu {
28namespace yat {
29namespace utility {
30
31  /**
32    Struct to be used to make compile-time decision that Iterator is
33    unweighted, which is the default.
34   */ 
35  struct unweighted_type {
36    typedef unweighted_type type;
37  };
38   
39  /**
40    Struct to be used to make compile-time decision that Iterator is
41    weighted. Some algorithms come in also in a weighted version in
42    this tag could be used to decide on using them (rather than
43    unweighted cousin).
44   */ 
45  struct weighted_type {
46    typedef weighted_type type;
47  };
48
49  /**
50      All iterators default to unweighted type
51
52      \see Iterator and StrideIterator
53  */
54  template <class T>
55  struct weighted_iterator_traits {
56    typedef unweighted_type type;
57  };
58
59  /**
60    Metafunction that works on a pair weighted-unweighted types and
61    return weighted_type. The metafunction is specialized for
62    unweighted unweighted in which case unweighted is returned.
63   */
64  template <class T1, class T2>
65  struct unweighted_type_and {
66    typedef weighted_type type;
67  };
68
69  /**
70    Specialization that sets type to be unweighted when both arguments
71    are unweighted
72   */
73  template <>
74  struct unweighted_type_and<unweighted_type, unweighted_type> {
75    typedef unweighted_type type;
76  };
77
78  /**
79    struct used to determine if a pair of iterators should be treated
80    as weighted. If both iterators are unweighted, type is set to
81    unweighted else weighted.
82  */
83  template <class T1, class T2>
84  struct weighted_if_any2 {
85    typedef typename weighted_iterator_traits<T1>::type w_type1;
86    typedef typename weighted_iterator_traits<T2>::type w_type2;
87    typedef typename unweighted_type_and<w_type1, w_type2>::type type;
88  };
89
90  /**
91    Same as weighted_iterator_traits2 but for 3 arguments.
92   */
93  template <class T1, class T2, class T3>
94  struct weighted_if_any3 {
95    typedef typename weighted_if_any2<T1, T2>::type tmp;
96    typedef typename weighted_iterator_traits<T3>::type w_type3;
97    typedef typename unweighted_type_and<tmp, w_type3>::type type;
98  };
99
100  /// check (at compile time) that iterator is unweighted.
101  inline void check_iterator_is_unweighted(unweighted_type x){} 
102
103  /**
104     check (at compile time) that iterator \a iter is unweighted. This
105     function is strictly not needed, but exists only for convenience.
106   */
107  template <class Iter>
108  void check_iterator_is_unweighted(Iter iter) 
109  { check_iterator_is_unweighted(typename 
110                                 weighted_iterator_traits<Iter>::type());
111  }
112
113
114  /**
115     \brief traits to make unweighted iterator work in as a weighted
116
117     This class must be implemented for every iterator that can be weighted.
118
119     \see StrideIterator and Iterator
120   */ 
121  template <class Iter>
122  struct iterator_traits {
123    // Peter, perhaps these should be templatized, but for now return
124    // type double is hard coded.
125    /**
126       \return data that is *iter
127    */
128    double data(Iter iter) const 
129    { check_iterator_is_unweighted(iter); return *iter; }
130
131    /**
132       \return 1.0
133    */
134    double weight(Iter iter) const 
135    { check_iterator_is_unweighted(iter); return 1.0; }
136
137  };
138
139}}} // of namespace utility, yat, and theplu
140
141#endif
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