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- .. Distributed under the Boost
- .. Software License, Version 1.0. (See accompanying
- .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- +++++++++++++++++
- Iterator Traits
- +++++++++++++++++
- :Author: David Abrahams
- :Contact: dave@boost-consulting.com
- :organization: `Boost Consulting`_
- :date: $Date$
- :copyright: Copyright David Abrahams 2004.
- .. _`Boost Consulting`: http://www.boost-consulting.com
- :abstract: Header ``<boost/iterator/iterator_traits.hpp>`` provides
- the ability to access an iterator's associated types using
- MPL-compatible metafunctions_.
- .. _metafunctions: ../../mpl/doc/index.html#metafunctions
- Overview
- ========
- ``std::iterator_traits`` provides access to five associated types
- of any iterator: its ``value_type``, ``reference``, ``pointer``,
- ``iterator_category``, and ``difference_type``. Unfortunately,
- such a "multi-valued" traits template can be difficult to use in a
- metaprogramming context. ``<boost/iterator/iterator_traits.hpp>``
- provides access to these types using a standard metafunctions_.
- Summary
- =======
- Header ``<boost/iterator/iterator_traits.hpp>``::
- template <class Iterator>
- struct iterator_value
- {
- typedef typename
- std::iterator_traits<Iterator>::value_type
- type;
- };
- template <class Iterator>
- struct iterator_reference
- {
- typedef typename
- std::iterator_traits<Iterator>::reference
- type;
- };
- template <class Iterator>
- struct iterator_pointer
- {
- typedef typename
- std::iterator_traits<Iterator>::pointer
- type;
- };
- template <class Iterator>
- struct iterator_difference
- {
- typedef typename
- detail::iterator_traits<Iterator>::difference_type
- type;
- };
- template <class Iterator>
- struct iterator_category
- {
- typedef typename
- detail::iterator_traits<Iterator>::iterator_category
- type;
- };
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