[857] | 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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