[857] | 1 | // Copyright David Abrahams 2003.
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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 | #ifndef COUNTING_ITERATOR_DWA200348_HPP
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| 6 | # define COUNTING_ITERATOR_DWA200348_HPP
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| 7 |
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| 8 | # include <boost/iterator/iterator_adaptor.hpp>
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| 9 | # include <boost/detail/numeric_traits.hpp>
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| 10 | # include <boost/mpl/bool.hpp>
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| 11 | # include <boost/mpl/if.hpp>
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| 12 | # include <boost/mpl/identity.hpp>
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| 13 | # include <boost/mpl/eval_if.hpp>
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| 14 |
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| 15 | namespace boost {
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| 16 |
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| 17 | template <
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| 18 | class Incrementable
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| 19 | , class CategoryOrTraversal
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| 20 | , class Difference
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| 21 | >
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| 22 | class counting_iterator;
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| 23 |
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| 24 | namespace detail
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| 25 | {
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| 26 | // Try to detect numeric types at compile time in ways compatible
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| 27 | // with the limitations of the compiler and library.
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| 28 | template <class T>
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| 29 | struct is_numeric_impl
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| 30 | {
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| 31 | // For a while, this wasn't true, but we rely on it below. This is a regression assert.
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| 32 | BOOST_STATIC_ASSERT(::boost::is_integral<char>::value);
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| 33 |
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| 34 | # ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
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| 35 |
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| 36 | BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<T>::is_specialized);
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| 37 |
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| 38 | # else
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| 39 |
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| 40 | # if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
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| 41 | BOOST_STATIC_CONSTANT(
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| 42 | bool, value = (
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| 43 | boost::is_convertible<int,T>::value
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| 44 | && boost::is_convertible<T,int>::value
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| 45 | ));
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| 46 | # else
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| 47 | BOOST_STATIC_CONSTANT(bool, value = ::boost::is_arithmetic<T>::value);
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| 48 | # endif
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| 49 |
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| 50 | # endif
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| 51 | };
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| 52 |
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| 53 | template <class T>
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| 54 | struct is_numeric
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| 55 | : mpl::bool_<(::boost::detail::is_numeric_impl<T>::value)>
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| 56 | {};
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| 57 |
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| 58 | # if defined(BOOST_HAS_LONG_LONG)
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| 59 | template <>
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| 60 | struct is_numeric< ::boost::long_long_type>
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| 61 | : mpl::true_ {};
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| 62 |
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| 63 | template <>
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| 64 | struct is_numeric< ::boost::ulong_long_type>
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| 65 | : mpl::true_ {};
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| 66 | # endif
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| 67 |
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| 68 | // Some compilers fail to have a numeric_limits specialization
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| 69 | template <>
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| 70 | struct is_numeric<wchar_t>
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| 71 | : mpl::true_ {};
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| 72 |
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| 73 | template <class T>
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| 74 | struct numeric_difference
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| 75 | {
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| 76 | typedef typename boost::detail::numeric_traits<T>::difference_type type;
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| 77 | };
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| 78 |
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| 79 | BOOST_STATIC_ASSERT(is_numeric<int>::value);
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| 80 |
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| 81 | template <class Incrementable, class CategoryOrTraversal, class Difference>
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| 82 | struct counting_iterator_base
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| 83 | {
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| 84 | typedef typename detail::ia_dflt_help<
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| 85 | CategoryOrTraversal
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| 86 | , mpl::eval_if<
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| 87 | is_numeric<Incrementable>
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| 88 | , mpl::identity<random_access_traversal_tag>
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| 89 | , iterator_traversal<Incrementable>
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| 90 | >
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| 91 | >::type traversal;
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| 92 |
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| 93 | typedef typename detail::ia_dflt_help<
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| 94 | Difference
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| 95 | , mpl::eval_if<
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| 96 | is_numeric<Incrementable>
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| 97 | , numeric_difference<Incrementable>
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| 98 | , iterator_difference<Incrementable>
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| 99 | >
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| 100 | >::type difference;
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| 101 |
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| 102 | typedef iterator_adaptor<
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| 103 | counting_iterator<Incrementable, CategoryOrTraversal, Difference> // self
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| 104 | , Incrementable // Base
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| 105 | , Incrementable // Value
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| 106 | # ifndef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
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| 107 | const // MSVC won't strip this. Instead we enable Thomas'
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| 108 | // criterion (see boost/iterator/detail/facade_iterator_category.hpp)
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| 109 | # endif
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| 110 | , traversal
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| 111 | , Incrementable const& // reference
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| 112 | , difference
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| 113 | > type;
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| 114 | };
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| 115 |
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| 116 | // Template class distance_policy_select -- choose a policy for computing the
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| 117 | // distance between counting_iterators at compile-time based on whether or not
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| 118 | // the iterator wraps an integer or an iterator, using "poor man's partial
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| 119 | // specialization".
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| 120 |
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| 121 | template <bool is_integer> struct distance_policy_select;
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| 122 |
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| 123 | // A policy for wrapped iterators
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| 124 | template <class Difference, class Incrementable1, class Incrementable2>
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| 125 | struct iterator_distance
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| 126 | {
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| 127 | static Difference distance(Incrementable1 x, Incrementable2 y)
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| 128 | {
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| 129 | return y - x;
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| 130 | }
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| 131 | };
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| 132 |
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| 133 | // A policy for wrapped numbers
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| 134 | template <class Difference, class Incrementable1, class Incrementable2>
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| 135 | struct number_distance
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| 136 | {
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| 137 | static Difference distance(Incrementable1 x, Incrementable2 y)
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| 138 | {
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| 139 | return numeric_distance(x, y);
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| 140 | }
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| 141 | };
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| 142 | }
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| 143 |
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| 144 | template <
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| 145 | class Incrementable
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| 146 | , class CategoryOrTraversal = use_default
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| 147 | , class Difference = use_default
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| 148 | >
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| 149 | class counting_iterator
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| 150 | : public detail::counting_iterator_base<
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| 151 | Incrementable, CategoryOrTraversal, Difference
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| 152 | >::type
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| 153 | {
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| 154 | typedef typename detail::counting_iterator_base<
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| 155 | Incrementable, CategoryOrTraversal, Difference
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| 156 | >::type super_t;
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| 157 |
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| 158 | friend class iterator_core_access;
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| 159 |
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| 160 | public:
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| 161 | typedef typename super_t::difference_type difference_type;
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| 162 |
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| 163 | counting_iterator() { }
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| 164 |
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| 165 | counting_iterator(counting_iterator const& rhs) : super_t(rhs.base()) {}
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| 166 |
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| 167 | counting_iterator(Incrementable x)
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| 168 | : super_t(x)
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| 169 | {
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| 170 | }
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| 171 |
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| 172 | # if 0
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| 173 | template<class OtherIncrementable>
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| 174 | counting_iterator(
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| 175 | counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& t
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| 176 | , typename enable_if_convertible<OtherIncrementable, Incrementable>::type* = 0
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| 177 | )
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| 178 | : super_t(t.base())
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| 179 | {}
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| 180 | # endif
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| 181 |
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| 182 | private:
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| 183 |
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| 184 | typename super_t::reference dereference() const
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| 185 | {
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| 186 | return this->base_reference();
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| 187 | }
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| 188 |
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| 189 | template <class OtherIncrementable>
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| 190 | difference_type
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| 191 | distance_to(counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& y) const
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| 192 | {
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| 193 | typedef typename mpl::if_<
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| 194 | detail::is_numeric<Incrementable>
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| 195 | , detail::number_distance<difference_type, Incrementable, OtherIncrementable>
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| 196 | , detail::iterator_distance<difference_type, Incrementable, OtherIncrementable>
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| 197 | >::type d;
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| 198 |
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| 199 | return d::distance(this->base(), y.base());
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| 200 | }
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| 201 | };
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| 202 |
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| 203 | // Manufacture a counting iterator for an arbitrary incrementable type
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| 204 | template <class Incrementable>
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| 205 | inline counting_iterator<Incrementable>
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| 206 | make_counting_iterator(Incrementable x)
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| 207 | {
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| 208 | typedef counting_iterator<Incrementable> result_t;
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| 209 | return result_t(x);
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| 210 | }
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| 211 |
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| 212 |
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| 213 | } // namespace boost::iterator
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| 214 |
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| 215 | #endif // COUNTING_ITERATOR_DWA200348_HPP
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