Chris@16: // Boost.Range library
Chris@16: //
Chris@16: //  Copyright Neil Groves 2007. Use, modification and
Chris@16: //  distribution is subject to the Boost Software License, Version
Chris@16: //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: //  http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: //
Chris@16: // For more information, see http://www.boost.org/libs/range/
Chris@16: //
Chris@16: #ifndef BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED
Chris@16: #define BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED
Chris@16: 
Chris@16: #include <boost/range/adaptor/argument_fwd.hpp>
Chris@16: #include <boost/range/iterator_range.hpp>
Chris@101: #include <boost/iterator/iterator_facade.hpp>
Chris@16: #include <iterator>
Chris@16: 
Chris@16: namespace boost
Chris@16: {
Chris@16:     namespace range_detail
Chris@16:     {
Chris@16:         // strided_iterator for wrapping a forward traversal iterator
Chris@16:         template<class BaseIterator, class Category>
Chris@16:         class strided_iterator
Chris@101:             : public iterator_facade<
Chris@16:                 strided_iterator<BaseIterator, Category>
Chris@101:                 , typename iterator_value<BaseIterator>::type
Chris@101:                 , forward_traversal_tag
Chris@101:                 , typename iterator_reference<BaseIterator>::type
Chris@101:                 , typename iterator_difference<BaseIterator>::type
Chris@16:             >
Chris@16:         {
Chris@16:             friend class ::boost::iterator_core_access;
Chris@16: 
Chris@101:             typedef iterator_facade<
Chris@101:                 strided_iterator<BaseIterator, Category>
Chris@101:                 , typename iterator_value<BaseIterator>::type
Chris@101:                 , forward_traversal_tag
Chris@101:                 , typename iterator_reference<BaseIterator>::type
Chris@101:                 , typename iterator_difference<BaseIterator>::type
Chris@101:             > super_t;
Chris@16: 
Chris@16:         public:
Chris@101:             typedef typename super_t::difference_type difference_type;
Chris@101:             typedef typename super_t::reference reference;
Chris@16:             typedef BaseIterator base_iterator;
Chris@101:             typedef std::forward_iterator_tag iterator_category;
Chris@16: 
Chris@16:             strided_iterator()
Chris@101:                 : m_it()
Chris@101:                 , m_last()
Chris@16:                 , m_stride()
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@101:             strided_iterator(base_iterator   it,
Chris@101:                              base_iterator   last,
Chris@101:                              difference_type stride)
Chris@101:                 : m_it(it)
Chris@16:                 , m_last(last)
Chris@16:                 , m_stride(stride)
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@16:             template<class OtherIterator>
Chris@101:             strided_iterator(
Chris@101:                 const strided_iterator<OtherIterator, Category>& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                     OtherIterator,
Chris@101:                     base_iterator
Chris@101:                 >::type* = 0
Chris@101:             )
Chris@101:                 : m_it(other.base())
Chris@16:                 , m_last(other.base_end())
Chris@16:                 , m_stride(other.get_stride())
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@101:             base_iterator base() const
Chris@101:             {
Chris@101:                 return m_it;
Chris@101:             }
Chris@101: 
Chris@101:             base_iterator base_end() const
Chris@101:             {
Chris@101:                 return m_last;
Chris@101:             }
Chris@101: 
Chris@101:             difference_type get_stride() const
Chris@101:             {
Chris@101:                 return m_stride;
Chris@101:             }
Chris@16: 
Chris@16:         private:
Chris@16:             void increment()
Chris@16:             {
Chris@101:                 for (difference_type i = 0;
Chris@101:                         (m_it != m_last) && (i < m_stride); ++i)
Chris@101:                 {
Chris@101:                     ++m_it;
Chris@101:                 }
Chris@16:             }
Chris@16: 
Chris@101:             reference dereference() const
Chris@101:             {
Chris@101:                 return *m_it;
Chris@101:             }
Chris@101: 
Chris@101:             template<class OtherIterator>
Chris@101:             bool equal(
Chris@101:                 const strided_iterator<OtherIterator, Category>& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                     OtherIterator,
Chris@101:                     base_iterator
Chris@101:                 >::type* = 0) const
Chris@101:             {
Chris@101:                 return m_it == other.m_it;
Chris@101:             }
Chris@101: 
Chris@101:             base_iterator m_it;
Chris@16:             base_iterator m_last;
Chris@16:             difference_type m_stride;
Chris@16:         };
Chris@16: 
Chris@16:         // strided_iterator for wrapping a bidirectional iterator
Chris@16:         template<class BaseIterator>
Chris@16:         class strided_iterator<BaseIterator, bidirectional_traversal_tag>
Chris@101:             : public iterator_facade<
Chris@16:                 strided_iterator<BaseIterator, bidirectional_traversal_tag>
Chris@101:                 , typename iterator_value<BaseIterator>::type
Chris@101:                 , bidirectional_traversal_tag
Chris@101:                 , typename iterator_reference<BaseIterator>::type
Chris@101:                 , typename iterator_difference<BaseIterator>::type
Chris@16:             >
Chris@16:         {
Chris@16:             friend class ::boost::iterator_core_access;
Chris@16: 
Chris@101:             typedef iterator_facade<
Chris@101:                 strided_iterator<BaseIterator, bidirectional_traversal_tag>
Chris@101:                 , typename iterator_value<BaseIterator>::type
Chris@101:                 , bidirectional_traversal_tag
Chris@101:                 , typename iterator_reference<BaseIterator>::type
Chris@101:                 , typename iterator_difference<BaseIterator>::type
Chris@101:             > super_t;
Chris@16:         public:
Chris@101:             typedef typename super_t::difference_type difference_type;
Chris@101:             typedef typename super_t::reference reference;
Chris@16:             typedef BaseIterator base_iterator;
Chris@101:             typedef typename boost::make_unsigned<difference_type>::type
Chris@101:                         size_type;
Chris@101:             typedef std::bidirectional_iterator_tag iterator_category;
Chris@16: 
Chris@16:             strided_iterator()
Chris@101:                 : m_it()
Chris@101:                 , m_offset()
Chris@101:                 , m_index()
Chris@16:                 , m_stride()
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@101:             strided_iterator(base_iterator   it,
Chris@101:                              size_type       index,
Chris@101:                              difference_type stride)
Chris@101:                 : m_it(it)
Chris@101:                 , m_offset()
Chris@101:                 , m_index(index)
Chris@16:                 , m_stride(stride)
Chris@16:             {
Chris@101:                 if (stride && ((m_index % stride) != 0))
Chris@101:                     m_index += (stride - (m_index % stride));
Chris@16:             }
Chris@16: 
Chris@16:             template<class OtherIterator>
Chris@101:             strided_iterator(
Chris@101:                 const strided_iterator<
Chris@101:                     OtherIterator,
Chris@101:                     bidirectional_traversal_tag
Chris@101:                 >& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                     OtherIterator,
Chris@101:                     base_iterator
Chris@101:                 >::type* = 0
Chris@101:             )
Chris@101:                 : m_it(other.base())
Chris@101:                 , m_offset(other.get_offset())
Chris@101:                 , m_index(other.get_index())
Chris@16:                 , m_stride(other.get_stride())
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@101:             base_iterator base() const
Chris@101:             {
Chris@101:                 return m_it;
Chris@101:             }
Chris@101: 
Chris@101:             difference_type get_offset() const
Chris@101:             {
Chris@101:                 return m_offset;
Chris@101:             }
Chris@101: 
Chris@101:             size_type get_index() const
Chris@101:             {
Chris@101:                 return m_index;
Chris@101:             }
Chris@101: 
Chris@101:             difference_type get_stride() const
Chris@101:             {
Chris@101:                 return m_stride;
Chris@101:             }
Chris@16: 
Chris@16:         private:
Chris@16:             void increment()
Chris@16:             {
Chris@101:                 m_offset += m_stride;
Chris@16:             }
Chris@16: 
Chris@16:             void decrement()
Chris@16:             {
Chris@101:                 m_offset -= m_stride;
Chris@16:             }
Chris@16: 
Chris@101:             reference dereference() const
Chris@101:             {
Chris@101:                 update();
Chris@101:                 return *m_it;
Chris@101:             }
Chris@101: 
Chris@101:             void update() const
Chris@101:             {
Chris@101:                 std::advance(m_it, m_offset);
Chris@101:                 m_index += m_offset;
Chris@101:                 m_offset = 0;
Chris@101:             }
Chris@101: 
Chris@101:             template<class OtherIterator>
Chris@101:             bool equal(
Chris@101:                 const strided_iterator<
Chris@101:                     OtherIterator,
Chris@101:                     bidirectional_traversal_tag
Chris@101:                 >& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                     OtherIterator,
Chris@101:                     base_iterator
Chris@101:                 >::type* = 0) const
Chris@101:             {
Chris@101:                 return (m_index + m_offset) ==
Chris@101:                             (other.get_index() + other.get_offset());
Chris@101:             }
Chris@101: 
Chris@101:             mutable base_iterator m_it;
Chris@101:             mutable difference_type m_offset;
Chris@101:             mutable size_type m_index;
Chris@16:             difference_type m_stride;
Chris@16:         };
Chris@16: 
Chris@16:         // strided_iterator implementation for wrapping a random access iterator
Chris@16:         template<class BaseIterator>
Chris@16:         class strided_iterator<BaseIterator, random_access_traversal_tag>
Chris@101:             : public iterator_facade<
Chris@101:                 strided_iterator<BaseIterator, random_access_traversal_tag>
Chris@101:                 , typename iterator_value<BaseIterator>::type
Chris@101:                 , random_access_traversal_tag
Chris@101:                 , typename iterator_reference<BaseIterator>::type
Chris@101:                 , typename iterator_difference<BaseIterator>::type
Chris@101:             >
Chris@16:         {
Chris@16:             friend class ::boost::iterator_core_access;
Chris@16: 
Chris@101:             typedef iterator_facade<
Chris@101:                 strided_iterator<BaseIterator, random_access_traversal_tag>
Chris@101:                 , typename iterator_value<BaseIterator>::type
Chris@101:                 , random_access_traversal_tag
Chris@101:                 , typename iterator_reference<BaseIterator>::type
Chris@101:                 , typename iterator_difference<BaseIterator>::type
Chris@101:             > super_t;
Chris@16:         public:
Chris@101:             typedef typename super_t::difference_type difference_type;
Chris@101:             typedef typename super_t::reference reference;
Chris@16:             typedef BaseIterator base_iterator;
Chris@101:             typedef std::random_access_iterator_tag iterator_category;
Chris@16: 
Chris@16:             strided_iterator()
Chris@101:                 : m_it()
Chris@101:                 , m_first()
Chris@16:                 , m_index(0)
Chris@16:                 , m_stride()
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@101:             strided_iterator(
Chris@101:                 base_iterator   first,
Chris@101:                 base_iterator   it,
Chris@101:                 difference_type stride
Chris@101:             )
Chris@101:                 : m_it(it)
Chris@16:                 , m_first(first)
Chris@101:                 , m_index(stride ? (it - first) : difference_type())
Chris@16:                 , m_stride(stride)
Chris@16:             {
Chris@101:                 if (stride && ((m_index % stride) != 0))
Chris@101:                     m_index += (stride - (m_index % stride));
Chris@16:             }
Chris@16: 
Chris@16:             template<class OtherIterator>
Chris@101:             strided_iterator(
Chris@101:                 const strided_iterator<
Chris@101:                     OtherIterator,
Chris@101:                     random_access_traversal_tag
Chris@101:                 >& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                     OtherIterator,
Chris@101:                     base_iterator
Chris@101:                 >::type* = 0
Chris@101:             )
Chris@101:                 : m_it(other.base())
Chris@16:                 , m_first(other.base_begin())
Chris@16:                 , m_index(other.get_index())
Chris@16:                 , m_stride(other.get_stride())
Chris@16:             {
Chris@16:             }
Chris@16: 
Chris@101:             base_iterator base_begin() const
Chris@101:             {
Chris@101:                 return m_first;
Chris@101:             }
Chris@101: 
Chris@101:             base_iterator base() const
Chris@101:             {
Chris@101:                 return m_it;
Chris@101:             }
Chris@101: 
Chris@101:             difference_type get_stride() const
Chris@101:             {
Chris@101:                 return m_stride;
Chris@101:             }
Chris@101: 
Chris@101:             difference_type get_index() const
Chris@101:             {
Chris@101:                 return m_index;
Chris@101:             }
Chris@16: 
Chris@16:         private:
Chris@16:             void increment()
Chris@16:             {
Chris@16:                 m_index += m_stride;
Chris@16:             }
Chris@16: 
Chris@16:             void decrement()
Chris@16:             {
Chris@16:                 m_index -= m_stride;
Chris@16:             }
Chris@16: 
Chris@16:             void advance(difference_type offset)
Chris@16:             {
Chris@101:                 m_index += (m_stride * offset);
Chris@101:             }
Chris@101: 
Chris@101:             // Implementation detail: only update the actual underlying iterator
Chris@101:             // at the point of dereference. This is done so that the increment
Chris@101:             // and decrement can overshoot the valid sequence as is required
Chris@101:             // by striding. Since we can do all comparisons just with the index
Chris@101:             // simply, and all dereferences must be within the valid range.
Chris@101:             void update() const
Chris@101:             {
Chris@101:                 m_it = m_first + m_index;
Chris@16:             }
Chris@16: 
Chris@16:             template<class OtherIterator>
Chris@101:             difference_type distance_to(
Chris@101:                 const strided_iterator<
Chris@101:                     OtherIterator,
Chris@101:                     random_access_traversal_tag
Chris@101:                 >& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                             OtherIterator, base_iterator>::type* = 0) const
Chris@16:             {
Chris@101:                 BOOST_ASSERT((other.m_index - m_index) % m_stride == difference_type());
Chris@101:                 return (other.m_index - m_index) / m_stride;
Chris@16:             }
Chris@16: 
Chris@101:             template<class OtherIterator>
Chris@101:             bool equal(
Chris@101:                 const strided_iterator<
Chris@101:                     OtherIterator,
Chris@101:                     random_access_traversal_tag
Chris@101:                 >& other,
Chris@101:                 typename enable_if_convertible<
Chris@101:                             OtherIterator, base_iterator>::type* = 0) const
Chris@16:             {
Chris@101:                 return m_index == other.m_index;
Chris@101:             }
Chris@101: 
Chris@101:             reference dereference() const
Chris@101:             {
Chris@101:                 update();
Chris@101:                 return *m_it;
Chris@16:             }
Chris@16: 
Chris@16:         private:
Chris@101:             mutable base_iterator m_it;
Chris@16:             base_iterator m_first;
Chris@16:             difference_type m_index;
Chris@16:             difference_type m_stride;
Chris@16:         };
Chris@16: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<Rng>::type,
Chris@101:             forward_traversal_tag
Chris@101:         >
Chris@101:         make_begin_strided_iterator(
Chris@101:             Rng& rng,
Chris@101:             Difference stride,
Chris@101:             forward_traversal_tag)
Chris@16:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 forward_traversal_tag
Chris@101:             >(boost::begin(rng), boost::end(rng), stride);
Chris@16:         }
Chris@16: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<const Rng>::type,
Chris@101:             forward_traversal_tag
Chris@101:         >
Chris@101:         make_begin_strided_iterator(
Chris@101:             const Rng& rng,
Chris@101:             Difference stride,
Chris@101:             forward_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<const Rng>::type,
Chris@101:                 forward_traversal_tag
Chris@101:             >(boost::begin(rng), boost::end(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<Rng>::type,
Chris@101:             forward_traversal_tag
Chris@101:         >
Chris@101:         make_end_strided_iterator(
Chris@101:             Rng& rng,
Chris@101:             Difference stride,
Chris@101:             forward_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 forward_traversal_tag
Chris@101:             >(boost::end(rng), boost::end(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<const Rng>::type,
Chris@101:             forward_traversal_tag
Chris@101:         >
Chris@101:         make_end_strided_iterator(
Chris@101:             const Rng& rng,
Chris@101:             Difference stride,
Chris@101:             forward_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<const Rng>::type,
Chris@101:                 forward_traversal_tag
Chris@101:             >(boost::end(rng), boost::end(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<Rng>::type,
Chris@101:             bidirectional_traversal_tag
Chris@101:         >
Chris@101:         make_begin_strided_iterator(
Chris@101:             Rng& rng,
Chris@101:             Difference stride,
Chris@101:             bidirectional_traversal_tag)
Chris@101:         {
Chris@101:             typedef typename range_difference<Rng>::type difference_type;
Chris@101: 
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 bidirectional_traversal_tag
Chris@101:             >(boost::begin(rng), difference_type(), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<const Rng>::type,
Chris@101:             bidirectional_traversal_tag
Chris@101:         >
Chris@101:         make_begin_strided_iterator(
Chris@101:             const Rng& rng,
Chris@101:             Difference stride,
Chris@101:             bidirectional_traversal_tag)
Chris@101:         {
Chris@101:             typedef typename range_difference<const Rng>::type difference_type;
Chris@101: 
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<const Rng>::type,
Chris@101:                 bidirectional_traversal_tag
Chris@101:             >(boost::begin(rng), difference_type(), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<Rng>::type,
Chris@101:             bidirectional_traversal_tag
Chris@101:         >
Chris@101:         make_end_strided_iterator(
Chris@101:             Rng& rng,
Chris@101:             Difference stride,
Chris@101:             bidirectional_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 bidirectional_traversal_tag
Chris@101:             >(boost::end(rng), boost::size(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<const Rng>::type,
Chris@101:             bidirectional_traversal_tag
Chris@101:         >
Chris@101:         make_end_strided_iterator(
Chris@101:             const Rng& rng,
Chris@101:             Difference stride,
Chris@101:             bidirectional_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<const Rng>::type,
Chris@101:                 bidirectional_traversal_tag
Chris@101:             >(boost::end(rng), boost::size(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<Rng>::type,
Chris@101:             random_access_traversal_tag
Chris@101:         >
Chris@101:         make_begin_strided_iterator(
Chris@101:             Rng& rng,
Chris@101:             Difference stride,
Chris@101:             random_access_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 random_access_traversal_tag
Chris@101:             >(boost::begin(rng), boost::begin(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<const Rng>::type,
Chris@101:             random_access_traversal_tag
Chris@101:         >
Chris@101:         make_begin_strided_iterator(
Chris@101:             const Rng& rng,
Chris@101:             Difference stride,
Chris@101:             random_access_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<const Rng>::type,
Chris@101:                 random_access_traversal_tag
Chris@101:             >(boost::begin(rng), boost::begin(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<Rng>::type,
Chris@101:             random_access_traversal_tag
Chris@101:         >
Chris@101:         make_end_strided_iterator(
Chris@101:             Rng& rng,
Chris@101:             Difference stride,
Chris@101:             random_access_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 random_access_traversal_tag
Chris@101:             >(boost::begin(rng), boost::end(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<class Rng, class Difference> inline
Chris@101:         strided_iterator<
Chris@101:             typename range_iterator<const Rng>::type,
Chris@101:             random_access_traversal_tag
Chris@101:         >
Chris@101:         make_end_strided_iterator(
Chris@101:             const Rng& rng,
Chris@101:             Difference stride,
Chris@101:             random_access_traversal_tag)
Chris@101:         {
Chris@101:             return strided_iterator<
Chris@101:                 typename range_iterator<const Rng>::type,
Chris@101:                 random_access_traversal_tag
Chris@101:             >(boost::begin(rng), boost::end(rng), stride);
Chris@101:         }
Chris@101: 
Chris@101:         template<
Chris@101:             class Rng,
Chris@101:             class Category =
Chris@101:                 typename iterator_traversal<
Chris@101:                     typename range_iterator<Rng>::type
Chris@101:                 >::type
Chris@101:         >
Chris@16:         class strided_range
Chris@16:             : public iterator_range<
Chris@101:                 range_detail::strided_iterator<
Chris@101:                     typename range_iterator<Rng>::type,
Chris@101:                     Category
Chris@101:                 >
Chris@101:             >
Chris@16:         {
Chris@16:             typedef range_detail::strided_iterator<
Chris@101:                 typename range_iterator<Rng>::type,
Chris@101:                 Category
Chris@101:             > iter_type;
Chris@16:             typedef iterator_range<iter_type> super_t;
Chris@16:         public:
Chris@16:             template<class Difference>
Chris@16:             strided_range(Difference stride, Rng& rng)
Chris@101:                 : super_t(
Chris@101:                     range_detail::make_begin_strided_iterator(
Chris@101:                         rng, stride,
Chris@101:                         typename iterator_traversal<
Chris@101:                             typename range_iterator<Rng>::type
Chris@101:                         >::type()),
Chris@101:                     range_detail::make_end_strided_iterator(
Chris@101:                         rng, stride,
Chris@101:                         typename iterator_traversal<
Chris@101:                             typename range_iterator<Rng>::type
Chris@101:                         >::type()))
Chris@16:             {
Chris@16:                 BOOST_ASSERT( stride >= 0 );
Chris@16:             }
Chris@16:         };
Chris@16: 
Chris@16:         template<class Difference>
Chris@16:         class strided_holder : public holder<Difference>
Chris@16:         {
Chris@16:         public:
Chris@101:             explicit strided_holder(Difference value)
Chris@101:                 : holder<Difference>(value)
Chris@101:             {
Chris@101:             }
Chris@16:         };
Chris@16: 
Chris@16:         template<class Rng, class Difference>
Chris@16:         inline strided_range<Rng>
Chris@16:         operator|(Rng& rng, const strided_holder<Difference>& stride)
Chris@16:         {
Chris@16:             return strided_range<Rng>(stride.val, rng);
Chris@16:         }
Chris@16: 
Chris@16:         template<class Rng, class Difference>
Chris@16:         inline strided_range<const Rng>
Chris@16:         operator|(const Rng& rng, const strided_holder<Difference>& stride)
Chris@16:         {
Chris@16:             return strided_range<const Rng>(stride.val, rng);
Chris@16:         }
Chris@16: 
Chris@16:     } // namespace range_detail
Chris@16: 
Chris@16:     using range_detail::strided_range;
Chris@16: 
Chris@16:     namespace adaptors
Chris@16:     {
Chris@16: 
Chris@16:         namespace
Chris@16:         {
Chris@16:             const range_detail::forwarder<range_detail::strided_holder>
Chris@101:                 strided = range_detail::forwarder<
Chris@101:                             range_detail::strided_holder>();
Chris@16:         }
Chris@16: 
Chris@16:         template<class Range, class Difference>
Chris@16:         inline strided_range<Range>
Chris@16:         stride(Range& rng, Difference step)
Chris@16:         {
Chris@16:             return strided_range<Range>(step, rng);
Chris@16:         }
Chris@16: 
Chris@16:         template<class Range, class Difference>
Chris@16:         inline strided_range<const Range>
Chris@16:         stride(const Range& rng, Difference step)
Chris@16:         {
Chris@16:             return strided_range<const Range>(step, rng);
Chris@16:         }
Chris@16: 
Chris@16:     } // namespace 'adaptors'
Chris@16: } // namespace 'boost'
Chris@16: 
Chris@16: #endif