add subtree-ish sources for 12.0.3

[ceph.git] / ceph / src / boost / libs / iterator / doc / quickbook / traits.qbk

[section:traits Iterator Traits]

`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_.

[h2 Synopsis]

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;
  };

[endsect]