1.. 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 Iterator Traits 7+++++++++++++++++ 8 9:Author: David Abrahams 10:Contact: dave@boost-consulting.com 11:organization: `Boost Consulting`_ 12:date: $Date$ 13:copyright: Copyright David Abrahams 2004. 14 15.. _`Boost Consulting`: http://www.boost-consulting.com 16 17:abstract: Header ``<boost/iterator/iterator_traits.hpp>`` provides 18 the ability to access an iterator's associated types using 19 MPL-compatible metafunctions_. 20 21.. _metafunctions: ../../mpl/doc/index.html#metafunctions 22 23Overview 24======== 25 26``std::iterator_traits`` provides access to five associated types 27of any iterator: its ``value_type``, ``reference``, ``pointer``, 28``iterator_category``, and ``difference_type``. Unfortunately, 29such a "multi-valued" traits template can be difficult to use in a 30metaprogramming context. ``<boost/iterator/iterator_traits.hpp>`` 31provides access to these types using a standard metafunctions_. 32 33Summary 34======= 35 36Header ``<boost/iterator/iterator_traits.hpp>``:: 37 38 template <class Iterator> 39 struct iterator_value 40 { 41 typedef typename 42 std::iterator_traits<Iterator>::value_type 43 type; 44 }; 45 46 template <class Iterator> 47 struct iterator_reference 48 { 49 typedef typename 50 std::iterator_traits<Iterator>::reference 51 type; 52 }; 53 54 55 template <class Iterator> 56 struct iterator_pointer 57 { 58 typedef typename 59 std::iterator_traits<Iterator>::pointer 60 type; 61 }; 62 63 template <class Iterator> 64 struct iterator_difference 65 { 66 typedef typename 67 detail::iterator_traits<Iterator>::difference_type 68 type; 69 }; 70 71 template <class Iterator> 72 struct iterator_category 73 { 74 typedef typename 75 detail::iterator_traits<Iterator>::iterator_category 76 type; 77 }; 78