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/Src/Dependencies/Boost/libs/iterator/doc/zip_iterator_ref.rst

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  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<typename IteratorTuple>
  8  class zip_iterator
  9  {  
 10
 11  public:
 12    typedef /* see below */ reference;
 13    typedef reference value_type;
 14    typedef value_type* pointer;
 15    typedef /* see below */ difference_type;
 16    typedef /* see below */ iterator_category;
 17
 18    zip_iterator();
 19    zip_iterator(IteratorTuple iterator_tuple);
 20
 21    template<typename OtherIteratorTuple>
 22    zip_iterator(
 23          const zip_iterator<OtherIteratorTuple>& other
 24        , typename enable_if_convertible<
 25                OtherIteratorTuple
 26              , IteratorTuple>::type* = 0     // exposition only
 27    );
 28
 29    const IteratorTuple& get_iterator_tuple() const;
 30
 31  private:
 32    IteratorTuple m_iterator_tuple;     // exposition only
 33  };
 34
 35  template<typename IteratorTuple> 
 36  zip_iterator<IteratorTuple> 
 37  make_zip_iterator(IteratorTuple t);
 38
 39
 40The ``reference`` member of ``zip_iterator`` is the type of the tuple
 41made of the reference types of the iterator types in the ``IteratorTuple``
 42argument.
 43
 44The ``difference_type`` member of ``zip_iterator`` is the ``difference_type``
 45of the first of the iterator types in the ``IteratorTuple`` argument.
 46
 47The ``iterator_category`` member of ``zip_iterator`` is convertible to the
 48minimum of the traversal categories of the iterator types in the ``IteratorTuple``
 49argument. For example, if the ``zip_iterator`` holds only vector
 50iterators, then ``iterator_category`` is convertible to 
 51``boost::random_access_traversal_tag``. If you add a list iterator, then
 52``iterator_category`` will be convertible to ``boost::bidirectional_traversal_tag``,
 53but no longer to ``boost::random_access_traversal_tag``.
 54
 55
 56``zip_iterator`` requirements
 57...................................
 58
 59All iterator types in the argument ``IteratorTuple`` shall model Readable Iterator.  
 60
 61
 62``zip_iterator`` models
 63.............................
 64
 65The resulting ``zip_iterator`` models Readable Iterator.
 66
 67The fact that the ``zip_iterator`` models only Readable Iterator does not 
 68prevent you from modifying the values that the individual iterators point
 69to. The tuple returned by the ``zip_iterator``'s ``operator*`` is a tuple 
 70constructed from the reference types of the individual iterators, not 
 71their value types. For example, if ``zip_it`` is a ``zip_iterator`` whose
 72first member iterator is an ``std::vector<double>::iterator``, then the
 73following line will modify the value which the first member iterator of
 74``zip_it`` currently points to:
 75
 76::
 77
 78    zip_it->get<0>() = 42.0;
 79
 80
 81Consider the set of standard traversal concepts obtained by taking
 82the most refined standard traversal concept modeled by each individual
 83iterator type in the ``IteratorTuple`` argument.The ``zip_iterator`` 
 84models the least refined standard traversal concept in this set.
 85
 86``zip_iterator<IteratorTuple1>`` is interoperable with
 87``zip_iterator<IteratorTuple2>`` if and only if ``IteratorTuple1``
 88is interoperable with ``IteratorTuple2``.
 89
 90
 91
 92``zip_iterator`` operations
 93.................................
 94
 95In addition to the operations required by the concepts modeled by
 96``zip_iterator``, ``zip_iterator`` provides the following
 97operations.
 98
 99
100``zip_iterator();``
101
102:Returns: An instance of ``zip_iterator`` with ``m_iterator_tuple``
103  default constructed.
104
105
106``zip_iterator(IteratorTuple iterator_tuple);``
107
108:Returns: An instance of ``zip_iterator`` with ``m_iterator_tuple``
109  initialized to ``iterator_tuple``.
110
111
112::
113
114    template<typename OtherIteratorTuple>
115    zip_iterator(
116          const zip_iterator<OtherIteratorTuple>& other
117        , typename enable_if_convertible<
118                OtherIteratorTuple
119              , IteratorTuple>::type* = 0     // exposition only
120    );
121
122:Returns: An instance of ``zip_iterator`` that is a copy of ``other``.
123:Requires: ``OtherIteratorTuple`` is implicitly convertible to ``IteratorTuple``.
124
125
126``const IteratorTuple& get_iterator_tuple() const;``
127
128:Returns: ``m_iterator_tuple``
129
130
131``reference operator*() const;``
132
133:Returns: A tuple consisting of the results of dereferencing all iterators in
134  ``m_iterator_tuple``.
135
136
137``zip_iterator& operator++();``
138
139:Effects: Increments each iterator in ``m_iterator_tuple``.
140:Returns: ``*this``
141
142
143``zip_iterator& operator--();``
144
145:Effects: Decrements each iterator in ``m_iterator_tuple``.
146:Returns: ``*this``
147
148::
149
150    template<typename IteratorTuple> 
151    zip_iterator<IteratorTuple> 
152    make_zip_iterator(IteratorTuple t);
153
154:Returns: An instance of ``zip_iterator<IteratorTuple>`` with ``m_iterator_tuple``
155  initialized to ``t``.