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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 | ||
23 | Overview | |
24 | ======== | |
25 | ||
26 | ``std::iterator_traits`` provides access to five associated types | |
27 | of any iterator: its ``value_type``, ``reference``, ``pointer``, | |
28 | ``iterator_category``, and ``difference_type``. Unfortunately, | |
29 | such a "multi-valued" traits template can be difficult to use in a | |
30 | metaprogramming context. ``<boost/iterator/iterator_traits.hpp>`` | |
31 | provides access to these types using a standard metafunctions_. | |
32 | ||
33 | Summary | |
34 | ======= | |
35 | ||
36 | Header ``<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 | }; |