1 | #ifndef _theplu_yat_utility_iterator_traits_ |
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2 | #define _theplu_yat_utility_iterator_traits_ |
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3 | |
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4 | // $Id: iterator_traits.h 3156 2014-01-03 08:06:02Z peter $ |
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5 | |
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6 | /* |
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7 | Copyright (C) 2007 Jari Häkkinen, Peter Johansson |
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8 | Copyright (C) 2008 Jari Häkkinen, Peter Johansson, Markus Ringnér |
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9 | Copyright (C) 2010, 2011, 2014 Peter Johansson |
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10 | |
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11 | This file is part of the yat library, http://dev.thep.lu.se/yat |
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12 | |
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13 | The yat library is free software; you can redistribute it and/or |
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14 | modify it under the terms of the GNU General Public License as |
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15 | published by the Free Software Foundation; either version 3 of the |
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16 | License, or (at your option) any later version. |
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17 | |
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18 | The yat library is distributed in the hope that it will be useful, |
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19 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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20 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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21 | General Public License for more details. |
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22 | |
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23 | You should have received a copy of the GNU General Public License |
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24 | along with yat. If not, see <http://www.gnu.org/licenses/>. |
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25 | */ |
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26 | |
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27 | #include "DataWeight.h" |
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28 | |
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29 | #include <boost/mpl/logical.hpp> |
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30 | #include <boost/type_traits/is_const.hpp> |
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31 | #include <boost/type_traits/is_convertible.hpp> |
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32 | #include <boost/type_traits/is_same.hpp> |
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33 | #include <boost/type_traits/remove_reference.hpp> |
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34 | #include <boost/utility/enable_if.hpp> |
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35 | |
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36 | #include <iterator> |
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37 | |
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38 | namespace theplu { |
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39 | namespace yat { |
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40 | namespace utility { |
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41 | |
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42 | /** |
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43 | Struct to be used to make compile-time decision that Iterator is |
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44 | unweighted, which is the default. |
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45 | */ |
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46 | struct unweighted_iterator_tag {}; |
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47 | |
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48 | /** |
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49 | Struct to be used to make compile-time decision that Iterator is |
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50 | weighted. Some algorithms come also in a weighted version and |
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51 | this tag could be used to decide on using them (rather than |
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52 | the corresponding unweighted algorithm). |
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53 | */ |
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54 | struct weighted_iterator_tag {}; |
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55 | |
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56 | |
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57 | /// \cond IGNORE_DOXYGEN |
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58 | |
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59 | namespace detail { |
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60 | /** |
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61 | \internal |
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62 | |
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63 | used in weighted_iterator_traits |
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64 | */ |
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65 | template <typename T, typename Enable = void> |
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66 | struct weighted_iterator_traits_detail { |
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67 | /** |
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68 | default is a iterator unweighted |
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69 | */ |
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70 | typedef unweighted_iterator_tag type; |
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71 | }; |
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72 | |
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73 | /** |
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74 | \internal |
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75 | |
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76 | specialization for iterators with value type convertible to DataWeight |
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77 | */ |
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78 | template <typename T> |
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79 | struct weighted_iterator_traits_detail<T, typename boost::enable_if<typename boost::is_convertible<T, DataWeight> >::type > { |
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80 | /** |
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81 | Iterators with value type convertible to DataWeight is weighted |
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82 | */ |
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83 | typedef weighted_iterator_tag type; |
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84 | }; |
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85 | |
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86 | } // namespace detail |
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87 | |
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88 | /// \endcond |
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89 | |
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90 | |
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91 | /** |
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92 | Metafunction to decide whether an Iterator is weighted or |
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93 | non-weighted. This (default) implementation returns |
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94 | unweighted_iterator_tag, unless value_type of Iterator is |
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95 | convertible to DataWeight in which case weighted_iterator_tag is |
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96 | returned. |
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97 | */ |
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98 | template <class Iterator> |
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99 | struct weighted_iterator_traits |
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100 | { |
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101 | private: |
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102 | typedef typename std::iterator_traits<Iterator>::value_type value; |
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103 | public: |
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104 | /** |
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105 | \return weighted_iterator_tag if Iterator::value_type is |
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106 | convertible to DataWeight |
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107 | */ |
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108 | typedef typename detail::weighted_iterator_traits_detail<value>::type type; |
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109 | }; |
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110 | |
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111 | |
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112 | /// \cond IGNORE_DOXYGEN |
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113 | namespace detail { |
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114 | /** |
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115 | \internal |
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116 | |
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117 | Metafunction that works on a pair weighted-unweighted types and |
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118 | return weighted_type. The metafunction is specialized for |
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119 | unweighted unweighted in which case unweighted is returned. |
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120 | */ |
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121 | template <class T1, class T2> |
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122 | struct unweighted_type_and { |
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123 | /** |
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124 | default return weighted_iterator_tag |
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125 | */ |
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126 | typedef weighted_iterator_tag type; |
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127 | }; |
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128 | |
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129 | /** |
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130 | \internal |
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131 | |
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132 | Specialization that sets type to be unweighted when both arguments |
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133 | are unweighted |
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134 | */ |
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135 | template <> |
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136 | struct unweighted_type_and<unweighted_iterator_tag, unweighted_iterator_tag> { |
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137 | /** |
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138 | return unweighted_iterator_tag |
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139 | */ |
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140 | typedef unweighted_iterator_tag type; |
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141 | }; |
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142 | } // namespace detail |
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143 | |
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144 | /// \endcond |
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145 | |
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146 | |
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147 | /** |
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148 | struct used to determine if a pair of iterators should be treated |
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149 | as weighted. If both iterators are unweighted, type is set to |
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150 | unweighted else weighted. |
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151 | */ |
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152 | template <class T1, class T2> |
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153 | struct weighted_if_any2 { |
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154 | private: |
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155 | typedef typename weighted_iterator_traits<T1>::type w_type1; |
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156 | typedef typename weighted_iterator_traits<T2>::type w_type2; |
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157 | public: |
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158 | /// return unweighted if both are unweighted |
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159 | typedef typename detail::unweighted_type_and<w_type1, w_type2>::type type; |
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160 | }; |
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161 | |
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162 | /** |
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163 | Same as weighted_iterator_traits2 but for 3 arguments. |
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164 | */ |
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165 | template <class T1, class T2, class T3> |
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166 | struct weighted_if_any3 { |
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167 | private: |
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168 | typedef typename weighted_if_any2<T1, T2>::type tmp; |
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169 | typedef typename weighted_iterator_traits<T3>::type w_type3; |
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170 | public: |
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171 | /// return unweighted if all are unweighted |
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172 | typedef typename detail::unweighted_type_and<tmp, w_type3>::type type; |
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173 | }; |
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174 | |
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175 | /// \cond IGNORE_DOXYGEN |
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176 | namespace detail { |
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177 | /** |
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178 | \internal |
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179 | |
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180 | check (at compile time) that iterator is unweighted. |
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181 | */ |
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182 | inline void |
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183 | check_iterator_is_unweighted(utility::unweighted_iterator_tag x){} |
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184 | } // namespace detail |
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185 | |
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186 | /// \endcond |
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187 | |
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188 | /** |
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189 | \brief check (at compile time) that iterator is unweighted. |
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190 | |
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191 | This function only compiles if iterator \a iter is unweighted. |
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192 | */ |
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193 | template <class Iter> |
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194 | void check_iterator_is_unweighted(Iter iter) |
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195 | { detail::check_iterator_is_unweighted(typename |
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196 | weighted_iterator_traits<Iter>::type()); |
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197 | } |
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198 | |
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199 | |
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200 | /// \cond IGNORE_DOXYGEN |
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201 | namespace detail { |
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202 | |
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203 | /** |
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204 | \internal |
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205 | |
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206 | The following block of code is used to detect if weighted |
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207 | iterators have functions 'double& data(void)' or if they only |
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208 | have the const version. |
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209 | |
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210 | The technique used is taken from http://www.martinecker.com/wiki/ |
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211 | */ |
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212 | typedef char yes; |
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213 | /** |
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214 | \internal |
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215 | |
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216 | This type (no) and type yes have different sizes and are used to |
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217 | differentiate between the two cases. |
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218 | */ |
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219 | typedef char (&no)[2]; |
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220 | /** |
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221 | \internal |
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222 | |
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223 | Overloaded function with template below. If there exists a |
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224 | function that returns double& that will used and otherwise |
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225 | overloaded template below will be used. This implementation and |
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226 | template return different types to differentiate the two cases. |
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227 | */ |
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228 | yes has_mutable(double&); |
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229 | /** |
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230 | \internal |
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231 | |
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232 | Function used in iter_has_mutable_data and |
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233 | iter_has_mutable_weight. The default case is used if function |
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234 | called (e.g. data() does not return double&. |
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235 | */ |
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236 | template<typename T> |
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237 | no has_mutable(const T&); |
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238 | |
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239 | /** |
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240 | \internal |
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241 | |
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242 | Struct to check if iterator has mutable data. *Iter must have a |
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243 | function data(). If that function returns double& value is |
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244 | true. |
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245 | */ |
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246 | template <class Iter> |
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247 | struct iter_has_mutable_data |
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248 | { |
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249 | /// instance of Iter |
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250 | static Iter iter; |
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251 | /// true if *iter has a function data() that returns double& |
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252 | static const bool value = |
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253 | sizeof(has_mutable((*iter).data())) == sizeof(yes); |
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254 | }; |
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255 | |
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256 | |
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257 | /** |
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258 | \internal |
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259 | |
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260 | Struct to check if iterator has mutable data. *Iter must have a |
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261 | function data(). If that function returns double& value is |
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262 | true. |
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263 | */ |
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264 | template <class Iter> |
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265 | struct iter_has_mutable_weight |
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266 | { |
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267 | /// instance of Iter |
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268 | static Iter iter; |
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269 | /// true if *iter has a function weight() that returns double& |
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270 | static const bool value = |
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271 | sizeof(has_mutable((*iter).weight())) == sizeof(yes); |
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272 | }; |
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273 | |
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274 | |
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275 | /** |
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276 | \internal |
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277 | |
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278 | Convenience meta-function. The struct is-a boost::true_type if |
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279 | Iter is a weighted iterator |
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280 | |
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281 | The purpose of the struct is to be used in boost::mpl, for |
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282 | example, in boost::mpl::and_. |
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283 | |
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284 | \see weighted_iterator_traits |
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285 | */ |
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286 | template<typename Iter> |
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287 | struct is_weighted |
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288 | : public boost::is_same<weighted_iterator_tag |
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289 | , typename weighted_iterator_traits<Iter>::type> |
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290 | {}; |
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291 | |
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292 | /** |
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293 | \internal |
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294 | |
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295 | same is_weighted but negated |
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296 | */ |
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297 | template<typename Iter> |
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298 | struct is_unweighted |
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299 | : public boost::is_same<unweighted_iterator_tag |
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300 | , typename weighted_iterator_traits<Iter>::type> |
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301 | {}; |
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302 | |
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303 | |
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304 | /** |
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305 | \internal |
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306 | |
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307 | Default implementation of iterator_traits_detail. Is supposed to |
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308 | be used for unweighted iterators. Weighted iterators use |
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309 | specialization below. |
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310 | */ |
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311 | template <typename Iter, typename Enable = void> |
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312 | struct iterator_traits_detail { |
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313 | /** |
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314 | for unweighted data_reference is reference |
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315 | */ |
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316 | typedef typename std::iterator_traits<Iter>::reference data_reference; |
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317 | |
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318 | /** |
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319 | for unweighted weight_reference is a double |
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320 | */ |
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321 | typedef const double weight_reference; |
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322 | |
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323 | /** |
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324 | \return * \a iter |
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325 | */ |
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326 | data_reference data(Iter iter) const { return *iter; } |
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327 | |
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328 | /** |
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329 | \return 1.0 |
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330 | */ |
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331 | weight_reference weight(Iter iter) const { return 1.0; } |
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332 | }; |
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333 | |
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334 | /** |
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335 | \internal |
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336 | Metafunction that returns double& if true and const double otherwise |
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337 | */ |
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338 | template<bool> |
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339 | struct mutable_reference { |
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340 | /// return const double if bool is false |
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341 | typedef const double type; |
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342 | }; |
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343 | |
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344 | /** |
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345 | \internal |
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346 | Specialization that returns double& in true case |
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347 | */ |
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348 | template<> |
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349 | struct mutable_reference<true> { |
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350 | /// return double& if bool is false |
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351 | typedef double& type; |
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352 | }; |
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353 | |
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354 | |
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355 | /** |
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356 | \internal |
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357 | |
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358 | Specialization for weighted iterators |
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359 | */ |
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360 | // we need remove_reference because is_const seems to not work on const& |
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361 | template <typename Iter> |
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362 | struct iterator_traits_detail<Iter, |
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363 | typename boost::enable_if<is_weighted<Iter> >::type > |
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364 | { |
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365 | /** |
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366 | data_reference is double& for mutable iterators and const |
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367 | double otherwise |
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368 | */ |
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369 | typedef |
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370 | typename mutable_reference<iter_has_mutable_data<Iter>::value>::type |
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371 | data_reference; |
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372 | |
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373 | /** |
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374 | weight_reference is double& for mutable iterators and const |
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375 | double otherwise |
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376 | */ |
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377 | typedef |
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378 | typename mutable_reference<iter_has_mutable_weight<Iter>::value>::type |
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379 | weight_reference; |
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380 | |
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381 | /** |
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382 | return data of \a iter |
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383 | */ |
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384 | data_reference data(Iter iter) const { return (*iter).data(); } |
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385 | |
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386 | /** |
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387 | return weight of \a iter |
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388 | */ |
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389 | weight_reference weight(Iter iter) const { return (*iter).weight(); } |
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390 | }; |
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391 | |
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392 | } // namespace detail |
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393 | |
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394 | /// \endcond |
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395 | |
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396 | |
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397 | /** |
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398 | The purpose of this class is to allow polymorphism between |
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399 | weighted and unweighted iterators. It allows to access data and |
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400 | weight for both weighted and unweighted iterators. |
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401 | |
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402 | For weighted iterators this class requires that *Iter has |
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403 | functions data(void) and weight(void). |
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404 | */ |
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405 | template <typename Iter> |
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406 | struct iterator_traits { |
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407 | private: |
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408 | typedef detail::iterator_traits_detail<Iter> traits; |
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409 | public: |
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410 | /** |
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411 | For unweighted iterator, data_reference is the same as |
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412 | std::iterator_traits<Iter>::reference, i.e., the data if the |
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413 | iterator is the same as *Iter. |
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414 | |
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415 | For weighted iterators, data_reference is double& if *Iter has |
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416 | a function double& data(void). Otherwise data_reference is |
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417 | const double. |
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418 | */ |
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419 | typedef typename traits::data_reference data_reference; |
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420 | |
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421 | /** |
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422 | For unweighted iterator, weight_reference is const double since |
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423 | the weight is always implicitly 1.0 and not mutable. |
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424 | |
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425 | For weighted iterators, weight_reference is double& if *Iter has |
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426 | a function double& weight(void). Otherwise weight_reference is |
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427 | const double. |
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428 | */ |
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429 | typedef typename traits::weight_reference weight_reference; |
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430 | |
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431 | /** |
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432 | \return data of iterator \a iter |
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433 | */ |
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434 | data_reference data(Iter iter) const |
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435 | { return traits().data(iter); } |
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436 | |
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437 | /** |
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438 | \return weight of iterator \a iter |
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439 | */ |
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440 | weight_reference weight(Iter iter) const |
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441 | { return traits().weight(iter); } |
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442 | |
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443 | }; |
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444 | |
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445 | }}} // of namespace utility, yat, and theplu |
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446 | |
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447 | #endif |
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