1 | // (C) Copyright Jeremy Siek 2002.
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2 | // Distributed under the Boost Software License, Version 1.0. (See
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3 | // accompanying file LICENSE_1_0.txt or copy at
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4 | // http://www.boost.org/LICENSE_1_0.txt)
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5 |
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6 | #ifndef BOOST_ITERATOR_CATEGORIES_HPP
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7 | # define BOOST_ITERATOR_CATEGORIES_HPP
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8 |
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9 | # include <boost/config.hpp>
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10 | # include <boost/detail/iterator.hpp>
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11 | # include <boost/iterator/detail/config_def.hpp>
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12 |
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13 | # include <boost/detail/workaround.hpp>
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14 |
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15 | # include <boost/mpl/eval_if.hpp>
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16 | # include <boost/mpl/identity.hpp>
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17 | # include <boost/mpl/placeholders.hpp>
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18 | # include <boost/mpl/aux_/lambda_support.hpp>
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19 |
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20 | # include <boost/type_traits/is_convertible.hpp>
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21 |
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22 | # include <boost/static_assert.hpp>
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23 |
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24 | namespace boost {
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25 |
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26 | //
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27 | // Traversal Categories
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28 | //
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29 |
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30 | struct no_traversal_tag {};
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31 |
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32 | struct incrementable_traversal_tag
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33 | : no_traversal_tag
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34 | {
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35 | // incrementable_traversal_tag() {}
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36 | // incrementable_traversal_tag(std::output_iterator_tag const&) {};
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37 | };
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38 |
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39 | struct single_pass_traversal_tag
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40 | : incrementable_traversal_tag
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41 | {
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42 | // single_pass_traversal_tag() {}
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43 | // single_pass_traversal_tag(std::input_iterator_tag const&) {};
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44 | };
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45 |
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46 | struct forward_traversal_tag
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47 | : single_pass_traversal_tag
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48 | {
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49 | // forward_traversal_tag() {}
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50 | // forward_traversal_tag(std::forward_iterator_tag const&) {};
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51 | };
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52 |
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53 | struct bidirectional_traversal_tag
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54 | : forward_traversal_tag
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55 | {
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56 | // bidirectional_traversal_tag() {};
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57 | // bidirectional_traversal_tag(std::bidirectional_iterator_tag const&) {};
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58 | };
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59 |
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60 | struct random_access_traversal_tag
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61 | : bidirectional_traversal_tag
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62 | {
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63 | // random_access_traversal_tag() {};
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64 | // random_access_traversal_tag(std::random_access_iterator_tag const&) {};
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65 | };
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66 |
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67 | namespace detail
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68 | {
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69 | //
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70 | // Convert a "strictly old-style" iterator category to a traversal
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71 | // tag. This is broken out into a separate metafunction to reduce
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72 | // the cost of instantiating iterator_category_to_traversal, below,
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73 | // for new-style types.
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74 | //
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75 | template <class Cat>
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76 | struct old_category_to_traversal
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77 | : mpl::eval_if<
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78 | is_convertible<Cat,std::random_access_iterator_tag>
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79 | , mpl::identity<random_access_traversal_tag>
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80 | , mpl::eval_if<
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81 | is_convertible<Cat,std::bidirectional_iterator_tag>
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82 | , mpl::identity<bidirectional_traversal_tag>
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83 | , mpl::eval_if<
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84 | is_convertible<Cat,std::forward_iterator_tag>
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85 | , mpl::identity<forward_traversal_tag>
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86 | , mpl::eval_if<
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87 | is_convertible<Cat,std::input_iterator_tag>
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88 | , mpl::identity<single_pass_traversal_tag>
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89 | , mpl::eval_if<
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90 | is_convertible<Cat,std::output_iterator_tag>
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91 | , mpl::identity<incrementable_traversal_tag>
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92 | , void
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93 | >
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94 | >
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95 | >
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96 | >
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97 | >
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98 | {};
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99 |
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100 | # if BOOST_WORKAROUND(BOOST_MSVC, == 1200)
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101 | template <>
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102 | struct old_category_to_traversal<int>
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103 | {
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104 | typedef int type;
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105 | };
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106 | # endif
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107 |
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108 | template <class Traversal>
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109 | struct pure_traversal_tag
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110 | : mpl::eval_if<
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111 | is_convertible<Traversal,random_access_traversal_tag>
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112 | , mpl::identity<random_access_traversal_tag>
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113 | , mpl::eval_if<
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114 | is_convertible<Traversal,bidirectional_traversal_tag>
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115 | , mpl::identity<bidirectional_traversal_tag>
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116 | , mpl::eval_if<
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117 | is_convertible<Traversal,forward_traversal_tag>
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118 | , mpl::identity<forward_traversal_tag>
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119 | , mpl::eval_if<
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120 | is_convertible<Traversal,single_pass_traversal_tag>
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121 | , mpl::identity<single_pass_traversal_tag>
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122 | , mpl::eval_if<
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123 | is_convertible<Traversal,incrementable_traversal_tag>
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124 | , mpl::identity<incrementable_traversal_tag>
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125 | , void
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126 | >
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127 | >
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128 | >
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129 | >
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130 | >
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131 | {
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132 | };
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133 |
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134 | # if BOOST_WORKAROUND(BOOST_MSVC, == 1200)
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135 | template <>
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136 | struct pure_traversal_tag<int>
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137 | {
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138 | typedef int type;
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139 | };
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140 | # endif
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141 |
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142 | } // namespace detail
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143 |
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144 |
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145 | //
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146 | // Convert an iterator category into a traversal tag
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147 | //
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148 | template <class Cat>
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149 | struct iterator_category_to_traversal
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150 | : mpl::eval_if< // if already convertible to a traversal tag, we're done.
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151 | is_convertible<Cat,incrementable_traversal_tag>
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152 | , mpl::identity<Cat>
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153 | , detail::old_category_to_traversal<Cat>
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154 | >
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155 | {};
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156 |
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157 | // Trait to get an iterator's traversal category
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158 | template <class Iterator = mpl::_1>
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159 | struct iterator_traversal
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160 | : iterator_category_to_traversal<
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161 | typename boost::detail::iterator_traits<Iterator>::iterator_category
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162 | >
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163 | {};
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164 |
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165 | # ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT
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166 | // Hack because BOOST_MPL_AUX_LAMBDA_SUPPORT doesn't seem to work
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167 | // out well. Instantiating the nested apply template also
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168 | // requires instantiating iterator_traits on the
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169 | // placeholder. Instead we just specialize it as a metafunction
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170 | // class.
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171 | template <>
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172 | struct iterator_traversal<mpl::_1>
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173 | {
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174 | template <class T>
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175 | struct apply : iterator_traversal<T>
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176 | {};
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177 | };
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178 | template <>
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179 | struct iterator_traversal<mpl::_>
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180 | : iterator_traversal<mpl::_1>
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181 | {};
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182 | # endif
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183 |
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184 | } // namespace boost
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185 |
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186 | #include <boost/iterator/detail/config_undef.hpp>
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187 |
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188 | #endif // BOOST_ITERATOR_CATEGORIES_HPP
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