ceph/src/boost/libs/iterator/doc/iterator_traits.rst

   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   };