source: trunk/yat/utility/iterator_traits.h @ 1088

Last change on this file since 1088 was 1088, checked in by Peter, 13 years ago

Closes #247. Removed IteratorWeighted? iterators over weighted container instead can use Iterator with a special Policy.

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 4.1 KB
Line 
1#ifndef _theplu_yat_utility_iterator_traits_
2#define _theplu_yat_utility_iterator_traits_
3
4// $Id: iterator_traits.h 1088 2008-02-14 14:26:19Z 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     \brief traits to make unweighted iterator work in as a weighted
123
124     This class must be implemented for every iterator that can be weighted.
125
126     \see StrideIterator and Iterator
127   */ 
128  template <class Iter>
129  struct iterator_traits {
130    // Peter, perhaps these should be templatized, but for now return
131    // type double is hard coded.
132    /**
133       \return data that is *iter
134    */
135    double data(Iter iter) const 
136    { check_iterator_is_unweighted(iter); return *iter; }
137
138    /**
139       \return 1.0
140    */
141    double weight(Iter iter) const 
142    { check_iterator_is_unweighted(iter); return 1.0; }
143
144  };
145
146}}} // of namespace utility, yat, and theplu
147
148#endif
Note: See TracBrowser for help on using the repository browser.