156 lines
4.6 KiB
ReStructuredText
156 lines
4.6 KiB
ReStructuredText
.. Copyright David Abrahams 2006. Distributed under the Boost
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.. Software License, Version 1.0. (See accompanying
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.. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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::
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template<typename IteratorTuple>
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class zip_iterator
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{
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public:
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typedef /* see below */ reference;
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typedef reference value_type;
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typedef value_type* pointer;
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typedef /* see below */ difference_type;
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typedef /* see below */ iterator_category;
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zip_iterator();
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zip_iterator(IteratorTuple iterator_tuple);
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template<typename OtherIteratorTuple>
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zip_iterator(
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const zip_iterator<OtherIteratorTuple>& other
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, typename enable_if_convertible<
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OtherIteratorTuple
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, IteratorTuple>::type* = 0 // exposition only
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);
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const IteratorTuple& get_iterator_tuple() const;
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private:
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IteratorTuple m_iterator_tuple; // exposition only
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};
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template<typename IteratorTuple>
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zip_iterator<IteratorTuple>
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make_zip_iterator(IteratorTuple t);
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The ``reference`` member of ``zip_iterator`` is the type of the tuple
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made of the reference types of the iterator types in the ``IteratorTuple``
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argument.
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The ``difference_type`` member of ``zip_iterator`` is the ``difference_type``
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of the first of the iterator types in the ``IteratorTuple`` argument.
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The ``iterator_category`` member of ``zip_iterator`` is convertible to the
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minimum of the traversal categories of the iterator types in the ``IteratorTuple``
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argument. For example, if the ``zip_iterator`` holds only vector
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iterators, then ``iterator_category`` is convertible to
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``boost::random_access_traversal_tag``. If you add a list iterator, then
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``iterator_category`` will be convertible to ``boost::bidirectional_traversal_tag``,
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but no longer to ``boost::random_access_traversal_tag``.
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``zip_iterator`` requirements
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...................................
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All iterator types in the argument ``IteratorTuple`` shall model Readable Iterator.
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``zip_iterator`` models
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.............................
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The resulting ``zip_iterator`` models Readable Iterator.
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The fact that the ``zip_iterator`` models only Readable Iterator does not
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prevent you from modifying the values that the individual iterators point
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to. The tuple returned by the ``zip_iterator``'s ``operator*`` is a tuple
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constructed from the reference types of the individual iterators, not
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their value types. For example, if ``zip_it`` is a ``zip_iterator`` whose
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first member iterator is an ``std::vector<double>::iterator``, then the
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following line will modify the value which the first member iterator of
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``zip_it`` currently points to:
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::
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zip_it->get<0>() = 42.0;
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Consider the set of standard traversal concepts obtained by taking
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the most refined standard traversal concept modeled by each individual
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iterator type in the ``IteratorTuple`` argument.The ``zip_iterator``
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models the least refined standard traversal concept in this set.
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``zip_iterator<IteratorTuple1>`` is interoperable with
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``zip_iterator<IteratorTuple2>`` if and only if ``IteratorTuple1``
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is interoperable with ``IteratorTuple2``.
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``zip_iterator`` operations
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.................................
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In addition to the operations required by the concepts modeled by
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``zip_iterator``, ``zip_iterator`` provides the following
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operations.
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``zip_iterator();``
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:Returns: An instance of ``zip_iterator`` with ``m_iterator_tuple``
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default constructed.
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``zip_iterator(IteratorTuple iterator_tuple);``
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:Returns: An instance of ``zip_iterator`` with ``m_iterator_tuple``
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initialized to ``iterator_tuple``.
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::
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template<typename OtherIteratorTuple>
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zip_iterator(
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const zip_iterator<OtherIteratorTuple>& other
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, typename enable_if_convertible<
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OtherIteratorTuple
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, IteratorTuple>::type* = 0 // exposition only
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);
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:Returns: An instance of ``zip_iterator`` that is a copy of ``other``.
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:Requires: ``OtherIteratorTuple`` is implicitly convertible to ``IteratorTuple``.
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``const IteratorTuple& get_iterator_tuple() const;``
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:Returns: ``m_iterator_tuple``
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``reference operator*() const;``
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:Returns: A tuple consisting of the results of dereferencing all iterators in
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``m_iterator_tuple``.
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``zip_iterator& operator++();``
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:Effects: Increments each iterator in ``m_iterator_tuple``.
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:Returns: ``*this``
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``zip_iterator& operator--();``
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:Effects: Decrements each iterator in ``m_iterator_tuple``.
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:Returns: ``*this``
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::
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template<typename IteratorTuple>
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zip_iterator<IteratorTuple>
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make_zip_iterator(IteratorTuple t);
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:Returns: An instance of ``zip_iterator<IteratorTuple>`` with ``m_iterator_tuple``
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initialized to ``t``.
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