ceph/src/boost/libs/iterator/doc/quickbook/traits.qbk

   1
   2 [section:traits Iterator Traits]
   3
   4 `std::iterator_traits` provides access to five associated types
   5 of any iterator: its `value_type`, `reference`, `pointer`,
   6 `iterator_category`, and `difference_type`.  Unfortunately,
   7 such a "multi-valued" traits template can be difficult to use in a
   8 metaprogramming context.  `<boost/iterator/iterator_traits.hpp>`
   9 provides access to these types using a standard metafunctions_.
  10
  11 [h2 Synopsis]
  12
  13 Header `<boost/iterator/iterator_traits.hpp>`:
  14
  15   template <class Iterator>
  16   struct iterator_value
  17   {
  18       typedef typename
  19         std::iterator_traits<Iterator>::value_type
  20       type;
  21   };
  22
  23   template <class Iterator>
  24   struct iterator_reference
  25   {
  26       typedef typename
  27         std::iterator_traits<Iterator>::reference
  28       type;
  29   };
  30
  31   template <class Iterator>
  32   struct iterator_pointer
  33   {
  34       typedef typename
  35         std::iterator_traits<Iterator>::pointer
  36       type;
  37   };
  38
  39   template <class Iterator>
  40   struct iterator_difference
  41   {
  42       typedef typename
  43         detail::iterator_traits<Iterator>::difference_type
  44       type;
  45   };
  46
  47   template <class Iterator>
  48   struct iterator_category
  49   {
  50       typedef typename
  51         detail::iterator_traits<Iterator>::iterator_category
  52       type;
  53   };
  54
  55 [endsect]