| Brian Silverman | 5962333 | 2018-08-04 23:36:56 -0700 | [diff] [blame^] | 1 | .. Copyright David Abrahams 2006. Distributed under the Boost |
| 2 | .. Software License, Version 1.0. (See accompanying |
| 3 | .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
| 4 | |
| 5 | :: |
| 6 | |
| 7 | template < |
| 8 | class Incrementable |
| 9 | , class CategoryOrTraversal = use_default |
| 10 | , class Difference = use_default |
| 11 | > |
| 12 | class counting_iterator |
| 13 | { |
| 14 | public: |
| 15 | typedef Incrementable value_type; |
| 16 | typedef const Incrementable& reference; |
| 17 | typedef const Incrementable* pointer; |
| 18 | typedef /* see below */ difference_type; |
| 19 | typedef /* see below */ iterator_category; |
| 20 | |
| 21 | counting_iterator(); |
| 22 | counting_iterator(counting_iterator const& rhs); |
| 23 | explicit counting_iterator(Incrementable x); |
| 24 | Incrementable const& base() const; |
| 25 | reference operator*() const; |
| 26 | counting_iterator& operator++(); |
| 27 | counting_iterator& operator--(); |
| 28 | private: |
| 29 | Incrementable m_inc; // exposition |
| 30 | }; |
| 31 | |
| 32 | |
| 33 | If the ``Difference`` argument is ``use_default`` then |
| 34 | ``difference_type`` is an unspecified signed integral |
| 35 | type. Otherwise ``difference_type`` is ``Difference``. |
| 36 | |
| 37 | ``iterator_category`` is determined according to the following |
| 38 | algorithm: |
| 39 | |
| 40 | .. parsed-literal:: |
| 41 | |
| 42 | if (CategoryOrTraversal is not use_default) |
| 43 | return CategoryOrTraversal |
| 44 | else if (numeric_limits<Incrementable>::is_specialized) |
| 45 | return |iterator-category|_\ ( |
| 46 | random_access_traversal_tag, Incrementable, const Incrementable&) |
| 47 | else |
| 48 | return |iterator-category|_\ ( |
| 49 | iterator_traversal<Incrementable>::type, |
| 50 | Incrementable, const Incrementable&) |
| 51 | |
| 52 | [*Note:* implementers are encouraged to provide an implementation of |
| 53 | ``operator-`` and a ``difference_type`` that avoids overflows in |
| 54 | the cases where ``std::numeric_limits<Incrementable>::is_specialized`` |
| 55 | is true.] |
| 56 | |
| 57 | ``counting_iterator`` requirements |
| 58 | .................................. |
| 59 | |
| 60 | The ``Incrementable`` argument shall be Copy Constructible and Assignable. |
| 61 | |
| 62 | If ``iterator_category`` is convertible to ``forward_iterator_tag`` |
| 63 | or ``forward_traversal_tag``, the following must be well-formed:: |
| 64 | |
| 65 | Incrementable i, j; |
| 66 | ++i; // pre-increment |
| 67 | i == j; // operator equal |
| 68 | |
| 69 | |
| 70 | If ``iterator_category`` is convertible to |
| 71 | ``bidirectional_iterator_tag`` or ``bidirectional_traversal_tag``, |
| 72 | the following expression must also be well-formed:: |
| 73 | |
| 74 | --i |
| 75 | |
| 76 | If ``iterator_category`` is convertible to |
| 77 | ``random_access_iterator_tag`` or ``random_access_traversal_tag``, |
| 78 | the following must must also be valid:: |
| 79 | |
| 80 | counting_iterator::difference_type n; |
| 81 | i += n; |
| 82 | n = i - j; |
| 83 | i < j; |
| 84 | |
| 85 | ``counting_iterator`` models |
| 86 | ............................ |
| 87 | |
| 88 | Specializations of ``counting_iterator`` model Readable Lvalue |
| 89 | Iterator. In addition, they model the concepts corresponding to the |
| 90 | iterator tags to which their ``iterator_category`` is convertible. |
| 91 | Also, if ``CategoryOrTraversal`` is not ``use_default`` then |
| 92 | ``counting_iterator`` models the concept corresponding to the iterator |
| 93 | tag ``CategoryOrTraversal``. Otherwise, if |
| 94 | ``numeric_limits<Incrementable>::is_specialized``, then |
| 95 | ``counting_iterator`` models Random Access Traversal Iterator. |
| 96 | Otherwise, ``counting_iterator`` models the same iterator traversal |
| 97 | concepts modeled by ``Incrementable``. |
| 98 | |
| 99 | ``counting_iterator<X,C1,D1>`` is interoperable with |
| 100 | ``counting_iterator<Y,C2,D2>`` if and only if ``X`` is |
| 101 | interoperable with ``Y``. |
| 102 | |
| 103 | |
| 104 | |
| 105 | ``counting_iterator`` operations |
| 106 | ................................ |
| 107 | |
| 108 | In addition to the operations required by the concepts modeled by |
| 109 | ``counting_iterator``, ``counting_iterator`` provides the following |
| 110 | operations. |
| 111 | |
| 112 | |
| 113 | ``counting_iterator();`` |
| 114 | |
| 115 | :Requires: ``Incrementable`` is Default Constructible. |
| 116 | :Effects: Default construct the member ``m_inc``. |
| 117 | |
| 118 | |
| 119 | ``counting_iterator(counting_iterator const& rhs);`` |
| 120 | |
| 121 | :Effects: Construct member ``m_inc`` from ``rhs.m_inc``. |
| 122 | |
| 123 | |
| 124 | |
| 125 | ``explicit counting_iterator(Incrementable x);`` |
| 126 | |
| 127 | :Effects: Construct member ``m_inc`` from ``x``. |
| 128 | |
| 129 | |
| 130 | ``reference operator*() const;`` |
| 131 | |
| 132 | :Returns: ``m_inc`` |
| 133 | |
| 134 | |
| 135 | ``counting_iterator& operator++();`` |
| 136 | |
| 137 | :Effects: ``++m_inc`` |
| 138 | :Returns: ``*this`` |
| 139 | |
| 140 | |
| 141 | ``counting_iterator& operator--();`` |
| 142 | |
| 143 | :Effects: ``--m_inc`` |
| 144 | :Returns: ``*this`` |
| 145 | |
| 146 | |
| 147 | ``Incrementable const& base() const;`` |
| 148 | |
| 149 | :Returns: ``m_inc`` |