1 | // (C) Copyright David Abrahams 2002. |
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2 | // (C) Copyright Jeremy Siek 2002. |
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3 | // (C) Copyright Thomas Witt 2002. |
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4 | // Distributed under the Boost Software License, Version 1.0. (See |
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5 | // accompanying file LICENSE_1_0.txt or copy at |
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6 | // http://www.boost.org/LICENSE_1_0.txt) |
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7 | #ifndef BOOST_ITERATOR_ADAPTOR_23022003THW_HPP |
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8 | #define BOOST_ITERATOR_ADAPTOR_23022003THW_HPP |
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9 | |
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10 | #include <boost/static_assert.hpp> |
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11 | #include <boost/iterator.hpp> |
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12 | #include <boost/detail/iterator.hpp> |
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13 | |
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14 | #include <boost/iterator/iterator_categories.hpp> |
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15 | #include <boost/iterator/iterator_facade.hpp> |
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16 | #include <boost/iterator/detail/enable_if.hpp> |
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17 | |
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18 | #include <boost/mpl/and.hpp> |
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19 | #include <boost/mpl/not.hpp> |
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20 | #include <boost/mpl/or.hpp> |
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21 | |
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22 | #include <boost/type_traits/is_same.hpp> |
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23 | #include <boost/type_traits/is_convertible.hpp> |
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24 | |
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25 | #ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY |
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26 | # include <boost/type_traits/remove_reference.hpp> |
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27 | |
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28 | # if BOOST_WORKAROUND(__CODEGEARC__, BOOST_TESTED_AT(0x610)) |
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29 | # include <boost/type_traits/add_reference.hpp> |
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30 | # endif |
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31 | |
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32 | #else |
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33 | # include <boost/type_traits/add_reference.hpp> |
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34 | #endif |
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35 | |
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36 | #include <boost/iterator/detail/config_def.hpp> |
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37 | |
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38 | #include <boost/iterator/iterator_traits.hpp> |
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39 | |
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40 | namespace boost |
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41 | { |
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42 | // Used as a default template argument internally, merely to |
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43 | // indicate "use the default", this can also be passed by users |
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44 | // explicitly in order to specify that the default should be used. |
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45 | struct use_default; |
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46 | |
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47 | # ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
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48 | // the incompleteness of use_default causes massive problems for |
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49 | // is_convertible (naturally). This workaround is fortunately not |
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50 | // needed for vc6/vc7. |
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51 | template<class To> |
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52 | struct is_convertible<use_default,To> |
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53 | : mpl::false_ {}; |
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54 | # endif |
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55 | |
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56 | namespace detail |
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57 | { |
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58 | |
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59 | // |
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60 | // Result type used in enable_if_convertible meta function. |
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61 | // This can be an incomplete type, as only pointers to |
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62 | // enable_if_convertible< ... >::type are used. |
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63 | // We could have used void for this, but conversion to |
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64 | // void* is just to easy. |
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65 | // |
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66 | struct enable_type; |
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67 | } |
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68 | |
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69 | |
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70 | // |
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71 | // enable_if for use in adapted iterators constructors. |
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72 | // |
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73 | // In order to provide interoperability between adapted constant and |
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74 | // mutable iterators, adapted iterators will usually provide templated |
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75 | // conversion constructors of the following form |
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76 | // |
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77 | // template <class BaseIterator> |
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78 | // class adapted_iterator : |
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79 | // public iterator_adaptor< adapted_iterator<Iterator>, Iterator > |
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80 | // { |
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81 | // public: |
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82 | // |
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83 | // ... |
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84 | // |
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85 | // template <class OtherIterator> |
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86 | // adapted_iterator( |
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87 | // OtherIterator const& it |
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88 | // , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0); |
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89 | // |
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90 | // ... |
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91 | // }; |
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92 | // |
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93 | // enable_if_convertible is used to remove those overloads from the overload |
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94 | // set that cannot be instantiated. For all practical purposes only overloads |
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95 | // for constant/mutable interaction will remain. This has the advantage that |
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96 | // meta functions like boost::is_convertible do not return false positives, |
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97 | // as they can only look at the signature of the conversion constructor |
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98 | // and not at the actual instantiation. |
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99 | // |
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100 | // enable_if_interoperable can be safely used in user code. It falls back to |
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101 | // always enabled for compilers that don't support enable_if or is_convertible. |
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102 | // There is no need for compiler specific workarounds in user code. |
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103 | // |
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104 | // The operators implementation relies on boost::is_convertible not returning |
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105 | // false positives for user/library defined iterator types. See comments |
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106 | // on operator implementation for consequences. |
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107 | // |
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108 | # if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) |
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109 | |
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110 | template<typename From, typename To> |
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111 | struct enable_if_convertible |
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112 | { |
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113 | typedef typename mpl::if_< |
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114 | mpl::or_< |
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115 | is_same<From,To> |
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116 | , is_convertible<From, To> |
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117 | > |
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118 | , boost::detail::enable_type |
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119 | , int& |
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120 | >::type type; |
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121 | }; |
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122 | |
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123 | # elif defined(BOOST_NO_IS_CONVERTIBLE) || defined(BOOST_NO_SFINAE) |
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124 | |
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125 | template <class From, class To> |
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126 | struct enable_if_convertible |
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127 | { |
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128 | typedef boost::detail::enable_type type; |
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129 | }; |
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130 | |
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131 | # elif BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292)) && BOOST_MSVC > 1300 |
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132 | |
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133 | // For some reason vc7.1 needs us to "cut off" instantiation |
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134 | // of is_convertible in a few cases. |
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135 | template<typename From, typename To> |
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136 | struct enable_if_convertible |
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137 | : iterators::enable_if< |
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138 | mpl::or_< |
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139 | is_same<From,To> |
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140 | , is_convertible<From, To> |
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141 | > |
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142 | , boost::detail::enable_type |
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143 | > |
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144 | {}; |
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145 | |
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146 | # else |
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147 | |
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148 | template<typename From, typename To> |
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149 | struct enable_if_convertible |
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150 | : iterators::enable_if< |
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151 | is_convertible<From, To> |
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152 | , boost::detail::enable_type |
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153 | > |
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154 | {}; |
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155 | |
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156 | # endif |
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157 | |
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158 | // |
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159 | // Default template argument handling for iterator_adaptor |
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160 | // |
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161 | namespace detail |
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162 | { |
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163 | // If T is use_default, return the result of invoking |
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164 | // DefaultNullaryFn, otherwise return T. |
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165 | template <class T, class DefaultNullaryFn> |
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166 | struct ia_dflt_help |
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167 | : mpl::eval_if< |
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168 | is_same<T, use_default> |
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169 | , DefaultNullaryFn |
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170 | , mpl::identity<T> |
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171 | > |
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172 | { |
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173 | }; |
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174 | |
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175 | // A metafunction which computes an iterator_adaptor's base class, |
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176 | // a specialization of iterator_facade. |
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177 | template < |
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178 | class Derived |
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179 | , class Base |
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180 | , class Value |
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181 | , class Traversal |
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182 | , class Reference |
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183 | , class Difference |
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184 | > |
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185 | struct iterator_adaptor_base |
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186 | { |
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187 | typedef iterator_facade< |
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188 | Derived |
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189 | |
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190 | # ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY |
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191 | , typename boost::detail::ia_dflt_help< |
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192 | Value |
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193 | , mpl::eval_if< |
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194 | is_same<Reference,use_default> |
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195 | , iterator_value<Base> |
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196 | , remove_reference<Reference> |
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197 | > |
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198 | >::type |
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199 | # else |
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200 | , typename boost::detail::ia_dflt_help< |
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201 | Value, iterator_value<Base> |
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202 | >::type |
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203 | # endif |
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204 | |
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205 | , typename boost::detail::ia_dflt_help< |
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206 | Traversal |
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207 | , iterator_traversal<Base> |
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208 | >::type |
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209 | |
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210 | , typename boost::detail::ia_dflt_help< |
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211 | Reference |
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212 | , mpl::eval_if< |
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213 | is_same<Value,use_default> |
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214 | , iterator_reference<Base> |
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215 | , add_reference<Value> |
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216 | > |
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217 | >::type |
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218 | |
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219 | , typename boost::detail::ia_dflt_help< |
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220 | Difference, iterator_difference<Base> |
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221 | >::type |
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222 | > |
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223 | type; |
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224 | }; |
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225 | |
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226 | // workaround for aC++ CR JAGaf33512 |
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227 | template <class Tr1, class Tr2> |
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228 | inline void iterator_adaptor_assert_traversal () |
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229 | { |
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230 | BOOST_STATIC_ASSERT((is_convertible<Tr1, Tr2>::value)); |
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231 | } |
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232 | } |
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233 | |
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234 | // |
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235 | // Iterator Adaptor |
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236 | // |
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237 | // The parameter ordering changed slightly with respect to former |
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238 | // versions of iterator_adaptor The idea is that when the user needs |
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239 | // to fiddle with the reference type it is highly likely that the |
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240 | // iterator category has to be adjusted as well. Any of the |
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241 | // following four template arguments may be ommitted or explicitly |
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242 | // replaced by use_default. |
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243 | // |
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244 | // Value - if supplied, the value_type of the resulting iterator, unless |
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245 | // const. If const, a conforming compiler strips constness for the |
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246 | // value_type. If not supplied, iterator_traits<Base>::value_type is used |
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247 | // |
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248 | // Category - the traversal category of the resulting iterator. If not |
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249 | // supplied, iterator_traversal<Base>::type is used. |
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250 | // |
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251 | // Reference - the reference type of the resulting iterator, and in |
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252 | // particular, the result type of operator*(). If not supplied but |
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253 | // Value is supplied, Value& is used. Otherwise |
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254 | // iterator_traits<Base>::reference is used. |
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255 | // |
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256 | // Difference - the difference_type of the resulting iterator. If not |
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257 | // supplied, iterator_traits<Base>::difference_type is used. |
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258 | // |
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259 | template < |
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260 | class Derived |
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261 | , class Base |
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262 | , class Value = use_default |
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263 | , class Traversal = use_default |
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264 | , class Reference = use_default |
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265 | , class Difference = use_default |
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266 | > |
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267 | class iterator_adaptor |
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268 | : public boost::detail::iterator_adaptor_base< |
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269 | Derived, Base, Value, Traversal, Reference, Difference |
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270 | >::type |
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271 | { |
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272 | friend class iterator_core_access; |
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273 | |
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274 | protected: |
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275 | typedef typename boost::detail::iterator_adaptor_base< |
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276 | Derived, Base, Value, Traversal, Reference, Difference |
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277 | >::type super_t; |
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278 | public: |
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279 | iterator_adaptor() {} |
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280 | |
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281 | explicit iterator_adaptor(Base const &iter) |
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282 | : m_iterator(iter) |
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283 | { |
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284 | } |
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285 | |
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286 | typedef Base base_type; |
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287 | |
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288 | Base const& base() const |
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289 | { return m_iterator; } |
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290 | |
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291 | protected: |
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292 | // for convenience in derived classes |
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293 | typedef iterator_adaptor<Derived,Base,Value,Traversal,Reference,Difference> iterator_adaptor_; |
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294 | |
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295 | // |
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296 | // lvalue access to the Base object for Derived |
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297 | // |
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298 | Base const& base_reference() const |
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299 | { return m_iterator; } |
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300 | |
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301 | Base& base_reference() |
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302 | { return m_iterator; } |
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303 | |
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304 | private: |
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305 | // |
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306 | // Core iterator interface for iterator_facade. This is private |
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307 | // to prevent temptation for Derived classes to use it, which |
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308 | // will often result in an error. Derived classes should use |
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309 | // base_reference(), above, to get direct access to m_iterator. |
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310 | // |
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311 | typename super_t::reference dereference() const |
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312 | { return *m_iterator; } |
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313 | |
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314 | template < |
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315 | class OtherDerived, class OtherIterator, class V, class C, class R, class D |
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316 | > |
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317 | bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const |
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318 | { |
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319 | // Maybe readd with same_distance |
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320 | // BOOST_STATIC_ASSERT( |
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321 | // (detail::same_category_and_difference<Derived,OtherDerived>::value) |
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322 | // ); |
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323 | return m_iterator == x.base(); |
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324 | } |
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325 | |
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326 | typedef typename iterator_category_to_traversal< |
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327 | typename super_t::iterator_category |
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328 | >::type my_traversal; |
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329 | |
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330 | # define BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(cat) \ |
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331 | boost::detail::iterator_adaptor_assert_traversal<my_traversal, cat>(); |
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332 | |
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333 | void advance(typename super_t::difference_type n) |
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334 | { |
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335 | BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag) |
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336 | m_iterator += n; |
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337 | } |
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338 | |
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339 | void increment() { ++m_iterator; } |
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340 | |
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341 | void decrement() |
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342 | { |
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343 | BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(bidirectional_traversal_tag) |
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344 | --m_iterator; |
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345 | } |
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346 | |
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347 | template < |
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348 | class OtherDerived, class OtherIterator, class V, class C, class R, class D |
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349 | > |
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350 | typename super_t::difference_type distance_to( |
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351 | iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const |
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352 | { |
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353 | BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag) |
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354 | // Maybe readd with same_distance |
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355 | // BOOST_STATIC_ASSERT( |
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356 | // (detail::same_category_and_difference<Derived,OtherDerived>::value) |
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357 | // ); |
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358 | return y.base() - m_iterator; |
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359 | } |
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360 | |
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361 | # undef BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL |
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362 | |
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363 | private: // data members |
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364 | Base m_iterator; |
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365 | }; |
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366 | |
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367 | } // namespace boost |
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368 | |
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369 | #include <boost/iterator/detail/config_undef.hpp> |
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370 | |
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371 | #endif // BOOST_ITERATOR_ADAPTOR_23022003THW_HPP |
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