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78 lines
1.9 KiB
ReStructuredText
78 lines
1.9 KiB
ReStructuredText
.. 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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Iterator Traits
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+++++++++++++++++
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:Author: David Abrahams
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:Contact: dave@boost-consulting.com
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:organization: `Boost Consulting`_
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:date: $Date$
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:copyright: Copyright David Abrahams 2004.
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.. _`Boost Consulting`: http://www.boost-consulting.com
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:abstract: Header ``<boost/iterator/iterator_traits.hpp>`` provides
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the ability to access an iterator's associated types using
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MPL-compatible metafunctions_.
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.. _metafunctions: ../../mpl/doc/index.html#metafunctions
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Overview
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========
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``std::iterator_traits`` provides access to five associated types
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of any iterator: its ``value_type``, ``reference``, ``pointer``,
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``iterator_category``, and ``difference_type``. Unfortunately,
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such a "multi-valued" traits template can be difficult to use in a
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metaprogramming context. ``<boost/iterator/iterator_traits.hpp>``
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provides access to these types using a standard metafunctions_.
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Summary
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=======
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Header ``<boost/iterator/iterator_traits.hpp>``::
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template <class Iterator>
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struct iterator_value
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{
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typedef typename
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std::iterator_traits<Iterator>::value_type
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type;
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};
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template <class Iterator>
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struct iterator_reference
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{
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typedef typename
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std::iterator_traits<Iterator>::reference
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type;
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};
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template <class Iterator>
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struct iterator_pointer
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{
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typedef typename
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std::iterator_traits<Iterator>::pointer
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type;
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};
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template <class Iterator>
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struct iterator_difference
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{
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typedef typename
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detail::iterator_traits<Iterator>::difference_type
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type;
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};
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template <class Iterator>
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struct iterator_category
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{
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typedef typename
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detail::iterator_traits<Iterator>::iterator_category
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type;
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};
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