williamr@2: // Copyright David Abrahams 2003.
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: #ifndef COUNTING_ITERATOR_DWA200348_HPP
williamr@2: # define COUNTING_ITERATOR_DWA200348_HPP
williamr@2: 
williamr@2: # include <boost/iterator/iterator_adaptor.hpp>
williamr@2: # include <boost/detail/numeric_traits.hpp>
williamr@2: # include <boost/mpl/bool.hpp>
williamr@2: # include <boost/mpl/if.hpp>
williamr@2: # include <boost/mpl/identity.hpp>
williamr@2: # include <boost/mpl/eval_if.hpp>
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2: template <
williamr@2:     class Incrementable
williamr@2:   , class CategoryOrTraversal
williamr@2:   , class Difference
williamr@2: >
williamr@2: class counting_iterator;
williamr@2: 
williamr@2: namespace detail
williamr@2: {
williamr@2:   // Try to detect numeric types at compile time in ways compatible
williamr@2:   // with the limitations of the compiler and library.
williamr@2:   template <class T>
williamr@2:   struct is_numeric_impl
williamr@2:   {
williamr@2:       // For a while, this wasn't true, but we rely on it below. This is a regression assert.
williamr@2:       BOOST_STATIC_ASSERT(::boost::is_integral<char>::value);
williamr@2:       
williamr@2: # ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
williamr@2:       
williamr@2:       BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<T>::is_specialized);
williamr@2:       
williamr@2: # else
williamr@2:       
williamr@2: #  if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
williamr@2:       BOOST_STATIC_CONSTANT(
williamr@2:           bool, value = (
williamr@2:               boost::is_convertible<int,T>::value
williamr@2:            && boost::is_convertible<T,int>::value
williamr@2:       ));
williamr@2: #  else
williamr@2:     BOOST_STATIC_CONSTANT(bool, value = ::boost::is_arithmetic<T>::value);
williamr@2: #  endif
williamr@2:       
williamr@2: # endif
williamr@2:   };
williamr@2: 
williamr@2:   template <class T>
williamr@2:   struct is_numeric
williamr@2:     : mpl::bool_<(::boost::detail::is_numeric_impl<T>::value)>
williamr@2:   {};
williamr@2: 
williamr@2: #  if defined(BOOST_HAS_LONG_LONG)
williamr@2:   template <>
williamr@2:   struct is_numeric< ::boost::long_long_type>
williamr@2:     : mpl::true_ {};
williamr@2:   
williamr@2:   template <>
williamr@2:   struct is_numeric< ::boost::ulong_long_type>
williamr@2:     : mpl::true_ {};
williamr@2: #  endif
williamr@2: 
williamr@2:   // Some compilers fail to have a numeric_limits specialization
williamr@2:   template <>
williamr@2:   struct is_numeric<wchar_t>
williamr@2:     : mpl::true_ {};
williamr@2:   
williamr@2:   template <class T>
williamr@2:   struct numeric_difference
williamr@2:   {
williamr@2:       typedef typename boost::detail::numeric_traits<T>::difference_type type;
williamr@2:   };
williamr@2: 
williamr@2:   BOOST_STATIC_ASSERT(is_numeric<int>::value);
williamr@2:   
williamr@2:   template <class Incrementable, class CategoryOrTraversal, class Difference>
williamr@2:   struct counting_iterator_base
williamr@2:   {
williamr@2:       typedef typename detail::ia_dflt_help<
williamr@2:           CategoryOrTraversal
williamr@2:         , mpl::eval_if<
williamr@2:               is_numeric<Incrementable>
williamr@2:             , mpl::identity<random_access_traversal_tag>
williamr@2:             , iterator_traversal<Incrementable>
williamr@2:           >
williamr@2:       >::type traversal;
williamr@2:       
williamr@2:       typedef typename detail::ia_dflt_help<
williamr@2:           Difference
williamr@2:         , mpl::eval_if<
williamr@2:               is_numeric<Incrementable>
williamr@2:             , numeric_difference<Incrementable>
williamr@2:             , iterator_difference<Incrementable>
williamr@2:           >
williamr@2:       >::type difference;
williamr@2:       
williamr@2:       typedef iterator_adaptor<
williamr@2:           counting_iterator<Incrementable, CategoryOrTraversal, Difference> // self
williamr@2:         , Incrementable                                           // Base
williamr@2:         , Incrementable                                           // Value
williamr@2: # ifndef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
williamr@2:           const  // MSVC won't strip this.  Instead we enable Thomas'
williamr@2:                  // criterion (see boost/iterator/detail/facade_iterator_category.hpp)
williamr@2: # endif 
williamr@2:         , traversal
williamr@2:         , Incrementable const&                                    // reference
williamr@2:         , difference
williamr@2:       > type;
williamr@2:   };
williamr@2: 
williamr@2:   // Template class distance_policy_select -- choose a policy for computing the
williamr@2:   // distance between counting_iterators at compile-time based on whether or not
williamr@2:   // the iterator wraps an integer or an iterator, using "poor man's partial
williamr@2:   // specialization".
williamr@2: 
williamr@2:   template <bool is_integer> struct distance_policy_select;
williamr@2: 
williamr@2:   // A policy for wrapped iterators
williamr@2:   template <class Difference, class Incrementable1, class Incrementable2>
williamr@2:   struct iterator_distance
williamr@2:   {
williamr@2:       static Difference distance(Incrementable1 x, Incrementable2 y)
williamr@2:       {
williamr@2:           return y - x;
williamr@2:       }
williamr@2:   };
williamr@2: 
williamr@2:   // A policy for wrapped numbers
williamr@2:   template <class Difference, class Incrementable1, class Incrementable2>
williamr@2:   struct number_distance
williamr@2:   {
williamr@2:       static Difference distance(Incrementable1 x, Incrementable2 y)
williamr@2:       {
williamr@2:           return numeric_distance(x, y);
williamr@2:       }
williamr@2:   };
williamr@2: }
williamr@2: 
williamr@2: template <
williamr@2:     class Incrementable
williamr@2:   , class CategoryOrTraversal = use_default
williamr@2:   , class Difference = use_default
williamr@2: >
williamr@2: class counting_iterator
williamr@2:   : public detail::counting_iterator_base<
williamr@2:         Incrementable, CategoryOrTraversal, Difference
williamr@2:     >::type
williamr@2: {
williamr@2:     typedef typename detail::counting_iterator_base<
williamr@2:         Incrementable, CategoryOrTraversal, Difference
williamr@2:     >::type super_t;
williamr@2:     
williamr@2:     friend class iterator_core_access;
williamr@2: 
williamr@2:  public:
williamr@2:     typedef typename super_t::difference_type difference_type;
williamr@2: 
williamr@2:     counting_iterator() { }
williamr@2:     
williamr@2:     counting_iterator(counting_iterator const& rhs) : super_t(rhs.base()) {}
williamr@2: 
williamr@2:     counting_iterator(Incrementable x)
williamr@2:       : super_t(x)
williamr@2:     {
williamr@2:     }
williamr@2: 
williamr@2: # if 0
williamr@2:     template<class OtherIncrementable>
williamr@2:     counting_iterator(
williamr@2:         counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& t
williamr@2:       , typename enable_if_convertible<OtherIncrementable, Incrementable>::type* = 0
williamr@2:     )
williamr@2:       : super_t(t.base())
williamr@2:     {}
williamr@2: # endif 
williamr@2: 
williamr@2:  private:
williamr@2:     
williamr@2:     typename super_t::reference dereference() const
williamr@2:     {
williamr@2:         return this->base_reference();
williamr@2:     }
williamr@2: 
williamr@2:     template <class OtherIncrementable>
williamr@2:     difference_type
williamr@2:     distance_to(counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& y) const
williamr@2:     {
williamr@2:       typedef typename mpl::if_<
williamr@2:           detail::is_numeric<Incrementable>
williamr@2:         , detail::number_distance<difference_type, Incrementable, OtherIncrementable>
williamr@2:         , detail::iterator_distance<difference_type, Incrementable, OtherIncrementable>
williamr@2:       >::type d;
williamr@2: 
williamr@2:       return d::distance(this->base(), y.base());
williamr@2:     }
williamr@2: };
williamr@2: 
williamr@2: // Manufacture a counting iterator for an arbitrary incrementable type
williamr@2: template <class Incrementable>
williamr@2: inline counting_iterator<Incrementable>
williamr@2: make_counting_iterator(Incrementable x)
williamr@2: {
williamr@2:   typedef counting_iterator<Incrementable> result_t;
williamr@2:   return result_t(x);
williamr@2: }
williamr@2: 
williamr@2: 
williamr@2: } // namespace boost::iterator
williamr@2: 
williamr@2: #endif // COUNTING_ITERATOR_DWA200348_HPP