Chris@16: // Copyright David Abrahams 2003.
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: #ifndef COUNTING_ITERATOR_DWA200348_HPP
Chris@16: # define COUNTING_ITERATOR_DWA200348_HPP
Chris@16: 
Chris@16: # include <boost/iterator/iterator_adaptor.hpp>
Chris@16: # include <boost/detail/numeric_traits.hpp>
Chris@16: # include <boost/mpl/bool.hpp>
Chris@16: # include <boost/mpl/if.hpp>
Chris@16: # include <boost/mpl/identity.hpp>
Chris@16: # include <boost/mpl/eval_if.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@101: namespace iterators {
Chris@16: 
Chris@16: template <
Chris@16:     class Incrementable
Chris@16:   , class CategoryOrTraversal
Chris@16:   , class Difference
Chris@16: >
Chris@16: class counting_iterator;
Chris@16: 
Chris@16: namespace detail
Chris@16: {
Chris@16:   // Try to detect numeric types at compile time in ways compatible
Chris@16:   // with the limitations of the compiler and library.
Chris@16:   template <class T>
Chris@16:   struct is_numeric_impl
Chris@16:   {
Chris@16:       // For a while, this wasn't true, but we rely on it below. This is a regression assert.
Chris@16:       BOOST_STATIC_ASSERT(::boost::is_integral<char>::value);
Chris@101: 
Chris@16: # ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
Chris@101: 
Chris@16:       BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<T>::is_specialized);
Chris@101: 
Chris@16: # else
Chris@101: 
Chris@16: #  if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
Chris@16:       BOOST_STATIC_CONSTANT(
Chris@16:           bool, value = (
Chris@16:               boost::is_convertible<int,T>::value
Chris@16:            && boost::is_convertible<T,int>::value
Chris@16:       ));
Chris@16: #  else
Chris@16:     BOOST_STATIC_CONSTANT(bool, value = ::boost::is_arithmetic<T>::value);
Chris@16: #  endif
Chris@101: 
Chris@16: # endif
Chris@16:   };
Chris@16: 
Chris@16:   template <class T>
Chris@16:   struct is_numeric
Chris@101:     : mpl::bool_<(::boost::iterators::detail::is_numeric_impl<T>::value)>
Chris@16:   {};
Chris@16: 
Chris@16: #  if defined(BOOST_HAS_LONG_LONG)
Chris@16:   template <>
Chris@16:   struct is_numeric< ::boost::long_long_type>
Chris@16:     : mpl::true_ {};
Chris@101: 
Chris@16:   template <>
Chris@16:   struct is_numeric< ::boost::ulong_long_type>
Chris@16:     : mpl::true_ {};
Chris@16: #  endif
Chris@16: 
Chris@16:   // Some compilers fail to have a numeric_limits specialization
Chris@16:   template <>
Chris@16:   struct is_numeric<wchar_t>
Chris@16:     : mpl::true_ {};
Chris@101: 
Chris@16:   template <class T>
Chris@16:   struct numeric_difference
Chris@16:   {
Chris@16:       typedef typename boost::detail::numeric_traits<T>::difference_type type;
Chris@16:   };
Chris@16: 
Chris@16:   BOOST_STATIC_ASSERT(is_numeric<int>::value);
Chris@101: 
Chris@16:   template <class Incrementable, class CategoryOrTraversal, class Difference>
Chris@16:   struct counting_iterator_base
Chris@16:   {
Chris@16:       typedef typename detail::ia_dflt_help<
Chris@16:           CategoryOrTraversal
Chris@16:         , mpl::eval_if<
Chris@16:               is_numeric<Incrementable>
Chris@16:             , mpl::identity<random_access_traversal_tag>
Chris@16:             , iterator_traversal<Incrementable>
Chris@16:           >
Chris@16:       >::type traversal;
Chris@101: 
Chris@16:       typedef typename detail::ia_dflt_help<
Chris@16:           Difference
Chris@16:         , mpl::eval_if<
Chris@16:               is_numeric<Incrementable>
Chris@16:             , numeric_difference<Incrementable>
Chris@16:             , iterator_difference<Incrementable>
Chris@16:           >
Chris@16:       >::type difference;
Chris@101: 
Chris@16:       typedef iterator_adaptor<
Chris@16:           counting_iterator<Incrementable, CategoryOrTraversal, Difference> // self
Chris@16:         , Incrementable                                           // Base
Chris@16:         , Incrementable                                           // Value
Chris@16: # ifndef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
Chris@16:           const  // MSVC won't strip this.  Instead we enable Thomas'
Chris@16:                  // criterion (see boost/iterator/detail/facade_iterator_category.hpp)
Chris@101: # endif
Chris@16:         , traversal
Chris@16:         , Incrementable const&                                    // reference
Chris@16:         , difference
Chris@16:       > type;
Chris@16:   };
Chris@16: 
Chris@16:   // Template class distance_policy_select -- choose a policy for computing the
Chris@16:   // distance between counting_iterators at compile-time based on whether or not
Chris@16:   // the iterator wraps an integer or an iterator, using "poor man's partial
Chris@16:   // specialization".
Chris@16: 
Chris@16:   template <bool is_integer> struct distance_policy_select;
Chris@16: 
Chris@16:   // A policy for wrapped iterators
Chris@16:   template <class Difference, class Incrementable1, class Incrementable2>
Chris@16:   struct iterator_distance
Chris@16:   {
Chris@16:       static Difference distance(Incrementable1 x, Incrementable2 y)
Chris@16:       {
Chris@16:           return y - x;
Chris@16:       }
Chris@16:   };
Chris@16: 
Chris@16:   // A policy for wrapped numbers
Chris@16:   template <class Difference, class Incrementable1, class Incrementable2>
Chris@16:   struct number_distance
Chris@16:   {
Chris@16:       static Difference distance(Incrementable1 x, Incrementable2 y)
Chris@16:       {
Chris@101:           return boost::detail::numeric_distance(x, y);
Chris@16:       }
Chris@16:   };
Chris@16: }
Chris@16: 
Chris@16: template <
Chris@16:     class Incrementable
Chris@16:   , class CategoryOrTraversal = use_default
Chris@16:   , class Difference = use_default
Chris@16: >
Chris@16: class counting_iterator
Chris@16:   : public detail::counting_iterator_base<
Chris@16:         Incrementable, CategoryOrTraversal, Difference
Chris@16:     >::type
Chris@16: {
Chris@16:     typedef typename detail::counting_iterator_base<
Chris@16:         Incrementable, CategoryOrTraversal, Difference
Chris@16:     >::type super_t;
Chris@101: 
Chris@16:     friend class iterator_core_access;
Chris@16: 
Chris@16:  public:
Chris@16:     typedef typename super_t::difference_type difference_type;
Chris@16: 
Chris@16:     counting_iterator() { }
Chris@101: 
Chris@16:     counting_iterator(counting_iterator const& rhs) : super_t(rhs.base()) {}
Chris@16: 
Chris@16:     counting_iterator(Incrementable x)
Chris@16:       : super_t(x)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16: # if 0
Chris@16:     template<class OtherIncrementable>
Chris@16:     counting_iterator(
Chris@16:         counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& t
Chris@16:       , typename enable_if_convertible<OtherIncrementable, Incrementable>::type* = 0
Chris@16:     )
Chris@16:       : super_t(t.base())
Chris@16:     {}
Chris@101: # endif
Chris@16: 
Chris@16:  private:
Chris@101: 
Chris@16:     typename super_t::reference dereference() const
Chris@16:     {
Chris@16:         return this->base_reference();
Chris@16:     }
Chris@16: 
Chris@16:     template <class OtherIncrementable>
Chris@16:     difference_type
Chris@16:     distance_to(counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& y) const
Chris@16:     {
Chris@16:       typedef typename mpl::if_<
Chris@16:           detail::is_numeric<Incrementable>
Chris@16:         , detail::number_distance<difference_type, Incrementable, OtherIncrementable>
Chris@16:         , detail::iterator_distance<difference_type, Incrementable, OtherIncrementable>
Chris@16:       >::type d;
Chris@16: 
Chris@16:       return d::distance(this->base(), y.base());
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: // Manufacture a counting iterator for an arbitrary incrementable type
Chris@16: template <class Incrementable>
Chris@16: inline counting_iterator<Incrementable>
Chris@16: make_counting_iterator(Incrementable x)
Chris@16: {
Chris@16:   typedef counting_iterator<Incrementable> result_t;
Chris@16:   return result_t(x);
Chris@16: }
Chris@16: 
Chris@101: } // namespace iterators
Chris@16: 
Chris@101: using iterators::counting_iterator;
Chris@101: using iterators::make_counting_iterator;
Chris@101: 
Chris@101: } // namespace boost
Chris@16: 
Chris@16: #endif // COUNTING_ITERATOR_DWA200348_HPP