forked from boostorg/range
strided adaptor rewritten to correct defects and optimise performance.
This commit is contained in:
Neil Groves
@@ -13,7 +13,7 @@
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#include <boost/range/adaptor/argument_fwd.hpp>
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#include <boost/range/iterator_range.hpp>
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#include <boost/iterator/iterator_adaptor.hpp>
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#include <boost/iterator/iterator_facade.hpp>
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#include <iterator>
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namespace boost
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@@ -23,59 +23,102 @@ namespace boost
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// strided_iterator for wrapping a forward traversal iterator
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template<class BaseIterator, class Category>
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class strided_iterator
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: public iterator_adaptor<
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: public iterator_facade<
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strided_iterator<BaseIterator, Category>
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, BaseIterator
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, use_default
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, boost::forward_traversal_tag
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, typename iterator_value<BaseIterator>::type
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, forward_traversal_tag
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, typename iterator_reference<BaseIterator>::type
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, typename iterator_difference<BaseIterator>::type
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>
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{
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friend class ::boost::iterator_core_access;
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typedef iterator_adaptor<
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strided_iterator<BaseIterator, Category>
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, BaseIterator
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, use_default
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, boost::forward_traversal_tag
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> super_t;
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typedef iterator_facade<
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strided_iterator<BaseIterator, Category>
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, typename iterator_value<BaseIterator>::type
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, forward_traversal_tag
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, typename iterator_reference<BaseIterator>::type
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, typename iterator_difference<BaseIterator>::type
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> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
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typedef typename super_t::difference_type difference_type;
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typedef typename super_t::reference reference;
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typedef BaseIterator base_iterator;
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typedef std::forward_iterator_tag iterator_category;
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strided_iterator()
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: m_last()
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: m_it()
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, m_last()
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, m_stride()
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{
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}
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strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride)
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: super_t(it)
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strided_iterator(base_iterator it,
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base_iterator last,
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difference_type stride)
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: m_it(it)
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, m_last(last)
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, m_stride(stride)
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{
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}
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator, Category>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0)
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: super_t(other)
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strided_iterator(
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const strided_iterator<OtherIterator, Category>& other,
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typename enable_if_convertible<
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OtherIterator,
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base_iterator
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>::type* = 0
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)
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: m_it(other.base())
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, m_last(other.base_end())
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, m_stride(other.get_stride())
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{
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}
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base_iterator base_end() const { return m_last; }
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difference_type get_stride() const { return m_stride; }
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base_iterator base() const
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{
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return m_it;
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}
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base_iterator base_end() const
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{
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return m_last;
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}
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difference_type get_stride() const
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{
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return m_stride;
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}
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private:
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void increment()
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{
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base_iterator& it = this->base_reference();
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for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i)
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++it;
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for (difference_type i = 0;
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(m_it != m_last) && (i < m_stride); ++i)
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{
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++m_it;
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}
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}
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reference dereference() const
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{
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return *m_it;
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}
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template<class OtherIterator>
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bool equal(
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const strided_iterator<OtherIterator, Category>& other,
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typename enable_if_convertible<
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OtherIterator,
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base_iterator
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>::type* = 0) const
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{
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return m_it == other.m_it;
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}
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base_iterator m_it;
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base_iterator m_last;
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difference_type m_stride;
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};
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@@ -83,214 +126,514 @@ namespace boost
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// strided_iterator for wrapping a bidirectional iterator
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template<class BaseIterator>
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class strided_iterator<BaseIterator, bidirectional_traversal_tag>
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: public iterator_adaptor<
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: public iterator_facade<
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strided_iterator<BaseIterator, bidirectional_traversal_tag>
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, BaseIterator
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, use_default
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, bidirectional_traversal_tag
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, typename iterator_value<BaseIterator>::type
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, bidirectional_traversal_tag
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, typename iterator_reference<BaseIterator>::type
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, typename iterator_difference<BaseIterator>::type
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>
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{
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friend class ::boost::iterator_core_access;
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typedef iterator_adaptor<
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strided_iterator<BaseIterator, bidirectional_traversal_tag>
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, BaseIterator
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, use_default
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, bidirectional_traversal_tag
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> super_t;
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typedef iterator_facade<
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strided_iterator<BaseIterator, bidirectional_traversal_tag>
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, typename iterator_value<BaseIterator>::type
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, bidirectional_traversal_tag
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, typename iterator_reference<BaseIterator>::type
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, typename iterator_difference<BaseIterator>::type
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> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
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typedef typename super_t::difference_type difference_type;
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typedef typename super_t::reference reference;
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typedef BaseIterator base_iterator;
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typedef typename boost::make_unsigned<difference_type>::type
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size_type;
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typedef std::bidirectional_iterator_tag iterator_category;
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strided_iterator()
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: m_first()
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, m_last()
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: m_it()
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, m_offset()
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, m_index()
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, m_stride()
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{
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}
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strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride)
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: super_t(it)
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, m_first(first)
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, m_last(last)
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strided_iterator(base_iterator it,
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size_type index,
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difference_type stride)
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: m_it(it)
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, m_offset()
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, m_index(index)
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, m_stride(stride)
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{
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if (stride && ((m_index % stride) != 0))
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m_index += (stride - (m_index % stride));
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}
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator, bidirectional_traversal_tag>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0)
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: super_t(other.base())
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, m_first(other.base_begin())
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, m_last(other.base_end())
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strided_iterator(
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const strided_iterator<
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OtherIterator,
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bidirectional_traversal_tag
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>& other,
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typename enable_if_convertible<
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OtherIterator,
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base_iterator
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>::type* = 0
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)
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: m_it(other.base())
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, m_offset(other.get_offset())
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, m_index(other.get_index())
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, m_stride(other.get_stride())
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{
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}
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base_iterator base_begin() const { return m_first; }
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base_iterator base_end() const { return m_last; }
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difference_type get_stride() const { return m_stride; }
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base_iterator base() const
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{
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return m_it;
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}
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difference_type get_offset() const
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{
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return m_offset;
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}
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size_type get_index() const
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{
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return m_index;
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}
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difference_type get_stride() const
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{
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return m_stride;
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}
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private:
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void increment()
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{
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base_iterator& it = this->base_reference();
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for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i)
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++it;
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m_offset += m_stride;
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}
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void decrement()
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{
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base_iterator& it = this->base_reference();
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for (difference_type i = 0; (it != m_first) && (i < m_stride); ++i)
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--it;
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m_offset -= m_stride;
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}
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base_iterator m_first;
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base_iterator m_last;
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reference dereference() const
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{
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update();
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return *m_it;
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}
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void update() const
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{
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std::advance(m_it, m_offset);
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m_index += m_offset;
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m_offset = 0;
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}
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template<class OtherIterator>
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bool equal(
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const strided_iterator<
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OtherIterator,
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bidirectional_traversal_tag
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>& other,
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typename enable_if_convertible<
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OtherIterator,
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base_iterator
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>::type* = 0) const
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{
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return (m_index + m_offset) ==
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(other.get_index() + other.get_offset());
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}
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mutable base_iterator m_it;
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mutable difference_type m_offset;
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mutable size_type m_index;
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difference_type m_stride;
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};
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// strided_iterator implementation for wrapping a random access iterator
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template<class BaseIterator>
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class strided_iterator<BaseIterator, random_access_traversal_tag>
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: public iterator_adaptor<
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strided_iterator<BaseIterator, random_access_traversal_tag>
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, BaseIterator
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, use_default
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, random_access_traversal_tag
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>
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: public iterator_facade<
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strided_iterator<BaseIterator, random_access_traversal_tag>
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, typename iterator_value<BaseIterator>::type
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, random_access_traversal_tag
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, typename iterator_reference<BaseIterator>::type
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, typename iterator_difference<BaseIterator>::type
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>
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{
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friend class ::boost::iterator_core_access;
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typedef iterator_adaptor<
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strided_iterator<BaseIterator, random_access_traversal_tag>
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, BaseIterator
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, use_default
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, random_access_traversal_tag
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> super_t;
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typedef iterator_facade<
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strided_iterator<BaseIterator, random_access_traversal_tag>
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, typename iterator_value<BaseIterator>::type
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, random_access_traversal_tag
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, typename iterator_reference<BaseIterator>::type
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, typename iterator_difference<BaseIterator>::type
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> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME super_t::difference_type difference_type;
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typedef typename super_t::difference_type difference_type;
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typedef typename super_t::reference reference;
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typedef BaseIterator base_iterator;
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typedef std::random_access_iterator_tag iterator_category;
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strided_iterator()
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: m_first()
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, m_last()
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: m_it()
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, m_first()
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, m_index(0)
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, m_stride()
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{
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}
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strided_iterator(BaseIterator first, BaseIterator it, BaseIterator last, difference_type stride)
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: super_t(it)
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strided_iterator(
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base_iterator first,
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base_iterator it,
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difference_type stride
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)
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: m_it(it)
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, m_first(first)
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, m_last(last)
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, m_index(stride ? (it - first) / stride : 0)
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, m_index(stride ? (it - first) : difference_type())
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, m_stride(stride)
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{
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if (stride && ((m_index % stride) != 0))
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m_index += (stride - (m_index % stride));
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}
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator, random_access_traversal_tag>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0)
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: super_t(other.base())
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strided_iterator(
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const strided_iterator<
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OtherIterator,
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random_access_traversal_tag
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>& other,
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typename enable_if_convertible<
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OtherIterator,
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base_iterator
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>::type* = 0
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)
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: m_it(other.base())
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, m_first(other.base_begin())
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, m_last(other.base_end())
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, m_index(other.get_index())
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, m_stride(other.get_stride())
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{
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}
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base_iterator base_begin() const { return m_first; }
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base_iterator base_end() const { return m_last; }
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difference_type get_stride() const { return m_stride; }
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difference_type get_index() const { return m_index; }
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base_iterator base_begin() const
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{
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return m_first;
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}
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base_iterator base() const
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{
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return m_it;
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}
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difference_type get_stride() const
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{
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return m_stride;
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}
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difference_type get_index() const
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{
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return m_index;
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}
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private:
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void increment()
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{
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m_index += m_stride;
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if (m_index < (m_last - m_first))
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this->base_reference() = m_first + m_index;
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else
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this->base_reference() = m_last;
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}
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void decrement()
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{
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m_index -= m_stride;
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if (m_index >= 0)
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this->base_reference() = m_first + m_index;
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else
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this->base_reference() = m_first;
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}
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void advance(difference_type offset)
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{
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offset *= m_stride;
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m_index += offset;
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if (m_index < 0)
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this->base_reference() = m_first;
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else if (m_index > (m_last - m_first))
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this->base_reference() = m_last;
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else
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this->base_reference() = m_first + m_index;
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m_index += (m_stride * offset);
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}
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// Implementation detail: only update the actual underlying iterator
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// at the point of dereference. This is done so that the increment
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// and decrement can overshoot the valid sequence as is required
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// by striding. Since we can do all comparisons just with the index
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// simply, and all dereferences must be within the valid range.
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void update() const
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{
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m_it = m_first + m_index;
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}
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template<class OtherIterator>
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difference_type distance_to(const strided_iterator<OtherIterator, random_access_traversal_tag>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0) const
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difference_type distance_to(
|
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const strided_iterator<
|
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OtherIterator,
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random_access_traversal_tag
|
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>& other,
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typename enable_if_convertible<
|
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OtherIterator, base_iterator>::type* = 0) const
|
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{
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if (other.base() >= this->base())
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return (other.base() - this->base() + (m_stride - 1)) / m_stride;
|
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return (other.base() - this->base() - (m_stride - 1)) / m_stride;
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BOOST_ASSERT((other.m_index - m_index) % m_stride == difference_type());
|
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return (other.m_index - m_index) / m_stride;
|
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}
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|
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bool equal(const strided_iterator& other) const
|
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template<class OtherIterator>
|
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bool equal(
|
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const strided_iterator<
|
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OtherIterator,
|
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random_access_traversal_tag
|
||||
>& other,
|
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typename enable_if_convertible<
|
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OtherIterator, base_iterator>::type* = 0) const
|
||||
{
|
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return this->base() == other.base();
|
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return m_index == other.m_index;
|
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}
|
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|
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reference dereference() const
|
||||
{
|
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update();
|
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return *m_it;
|
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}
|
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|
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private:
|
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mutable base_iterator m_it;
|
||||
base_iterator m_first;
|
||||
base_iterator m_last;
|
||||
difference_type m_index;
|
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difference_type m_stride;
|
||||
};
|
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|
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template<class BaseIterator, class Difference> inline
|
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strided_iterator<BaseIterator, BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type>
|
||||
make_strided_iterator(BaseIterator first, BaseIterator it,
|
||||
BaseIterator last, Difference stride)
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
forward_traversal_tag
|
||||
>
|
||||
make_begin_strided_iterator(
|
||||
Rng& rng,
|
||||
Difference stride,
|
||||
forward_traversal_tag)
|
||||
{
|
||||
BOOST_ASSERT( stride >= 0 );
|
||||
typedef BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type traversal_tag;
|
||||
return strided_iterator<BaseIterator, traversal_tag>(first, it, last, stride);
|
||||
return strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
forward_traversal_tag
|
||||
>(boost::begin(rng), boost::end(rng), stride);
|
||||
}
|
||||
|
||||
template< class Rng
|
||||
, class Category = BOOST_DEDUCED_TYPENAME iterator_traversal<
|
||||
BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type
|
||||
>::type
|
||||
>
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
forward_traversal_tag
|
||||
>
|
||||
make_begin_strided_iterator(
|
||||
const Rng& rng,
|
||||
Difference stride,
|
||||
forward_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
forward_traversal_tag
|
||||
>(boost::begin(rng), boost::end(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
forward_traversal_tag
|
||||
>
|
||||
make_end_strided_iterator(
|
||||
Rng& rng,
|
||||
Difference stride,
|
||||
forward_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
forward_traversal_tag
|
||||
>(boost::end(rng), boost::end(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
forward_traversal_tag
|
||||
>
|
||||
make_end_strided_iterator(
|
||||
const Rng& rng,
|
||||
Difference stride,
|
||||
forward_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
forward_traversal_tag
|
||||
>(boost::end(rng), boost::end(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>
|
||||
make_begin_strided_iterator(
|
||||
Rng& rng,
|
||||
Difference stride,
|
||||
bidirectional_traversal_tag)
|
||||
{
|
||||
typedef typename range_difference<Rng>::type difference_type;
|
||||
|
||||
return strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>(boost::begin(rng), difference_type(), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>
|
||||
make_begin_strided_iterator(
|
||||
const Rng& rng,
|
||||
Difference stride,
|
||||
bidirectional_traversal_tag)
|
||||
{
|
||||
typedef typename range_difference<const Rng>::type difference_type;
|
||||
|
||||
return strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>(boost::begin(rng), difference_type(), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>
|
||||
make_end_strided_iterator(
|
||||
Rng& rng,
|
||||
Difference stride,
|
||||
bidirectional_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>(boost::end(rng), boost::size(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>
|
||||
make_end_strided_iterator(
|
||||
const Rng& rng,
|
||||
Difference stride,
|
||||
bidirectional_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
bidirectional_traversal_tag
|
||||
>(boost::end(rng), boost::size(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>
|
||||
make_begin_strided_iterator(
|
||||
Rng& rng,
|
||||
Difference stride,
|
||||
random_access_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>(boost::begin(rng), boost::begin(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>
|
||||
make_begin_strided_iterator(
|
||||
const Rng& rng,
|
||||
Difference stride,
|
||||
random_access_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>(boost::begin(rng), boost::begin(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>
|
||||
make_end_strided_iterator(
|
||||
Rng& rng,
|
||||
Difference stride,
|
||||
random_access_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>(boost::begin(rng), boost::end(rng), stride);
|
||||
}
|
||||
|
||||
template<class Rng, class Difference> inline
|
||||
strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>
|
||||
make_end_strided_iterator(
|
||||
const Rng& rng,
|
||||
Difference stride,
|
||||
random_access_traversal_tag)
|
||||
{
|
||||
return strided_iterator<
|
||||
typename range_iterator<const Rng>::type,
|
||||
random_access_traversal_tag
|
||||
>(boost::begin(rng), boost::end(rng), stride);
|
||||
}
|
||||
|
||||
template<
|
||||
class Rng,
|
||||
class Category =
|
||||
typename iterator_traversal<
|
||||
typename range_iterator<Rng>::type
|
||||
>::type
|
||||
>
|
||||
class strided_range
|
||||
: public iterator_range<
|
||||
range_detail::strided_iterator<
|
||||
BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type,
|
||||
Category
|
||||
>
|
||||
>
|
||||
range_detail::strided_iterator<
|
||||
typename range_iterator<Rng>::type,
|
||||
Category
|
||||
>
|
||||
>
|
||||
{
|
||||
typedef range_detail::strided_iterator<
|
||||
BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type,
|
||||
Category
|
||||
> iter_type;
|
||||
typename range_iterator<Rng>::type,
|
||||
Category
|
||||
> iter_type;
|
||||
typedef iterator_range<iter_type> super_t;
|
||||
public:
|
||||
template<class Difference>
|
||||
strided_range(Difference stride, Rng& rng)
|
||||
: super_t(make_strided_iterator(boost::begin(rng), boost::begin(rng), boost::end(rng), stride),
|
||||
make_strided_iterator(boost::begin(rng), boost::end(rng), boost::end(rng), stride))
|
||||
: super_t(
|
||||
range_detail::make_begin_strided_iterator(
|
||||
rng, stride,
|
||||
typename iterator_traversal<
|
||||
typename range_iterator<Rng>::type
|
||||
>::type()),
|
||||
range_detail::make_end_strided_iterator(
|
||||
rng, stride,
|
||||
typename iterator_traversal<
|
||||
typename range_iterator<Rng>::type
|
||||
>::type()))
|
||||
{
|
||||
BOOST_ASSERT( stride >= 0 );
|
||||
}
|
||||
@@ -300,7 +643,10 @@ namespace boost
|
||||
class strided_holder : public holder<Difference>
|
||||
{
|
||||
public:
|
||||
explicit strided_holder(Difference value) : holder<Difference>(value) {}
|
||||
explicit strided_holder(Difference value)
|
||||
: holder<Difference>(value)
|
||||
{
|
||||
}
|
||||
};
|
||||
|
||||
template<class Rng, class Difference>
|
||||
@@ -327,7 +673,8 @@ namespace boost
|
||||
namespace
|
||||
{
|
||||
const range_detail::forwarder<range_detail::strided_holder>
|
||||
strided = range_detail::forwarder<range_detail::strided_holder>();
|
||||
strided = range_detail::forwarder<
|
||||
range_detail::strided_holder>();
|
||||
}
|
||||
|
||||
template<class Range, class Difference>
|
||||
|
||||
Reference in New Issue
Block a user