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