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72 lines
2.3 KiB
C++
72 lines
2.3 KiB
C++
// (C) Copyright Toon Knapen 2001. Permission to copy, use,
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// modify, sell and distribute this software is granted provided this
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// copyright notice appears in all copies. This software is provided
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// "as is" without express or implied warranty, and with no claim as
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// to its suitability for any purpose.
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//
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#include <boost/iterator_adaptors.hpp>
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namespace boost {
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template < typename OrderIt >
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struct permutation_iterator_policies : public default_iterator_policies
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{
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permutation_iterator_policies() {}
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permutation_iterator_policies(OrderIt order_it)
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: order_it_( order_it )
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{}
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template <class IteratorAdaptor>
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typename IteratorAdaptor::reference dereference(const IteratorAdaptor& x) const
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{ return *(x.base() + *order_it_); }
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template <class IteratorAdaptor>
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void increment(IteratorAdaptor& x)
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{ ++order_it_; }
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template <class IteratorAdaptor>
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void decrement(IteratorAdaptor& x)
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{ --order_it_; }
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template <class IteratorAdaptor, class DifferenceType>
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void advance(IteratorAdaptor& x, DifferenceType n)
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{ std::advance( order_it_, n ); }
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template <class IteratorAdaptor1, class IteratorAdaptor2>
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typename IteratorAdaptor1::difference_type
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distance(const IteratorAdaptor1& x, const IteratorAdaptor2& y) const
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{ return std::distance( x.policies().order_it_, y.policies().order_it_ ); }
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template <class IteratorAdaptor1, class IteratorAdaptor2>
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bool equal(const IteratorAdaptor1& x, const IteratorAdaptor2& y) const
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{ return x.policies().order_it_ == y.policies().order_it_; }
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OrderIt order_it_;
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};
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/// generate an iterator that will access the elements
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/// behind the random-access iterator RAIt in the
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/// order specified by the OrderIt iterator.
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/// preconditions:
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/// The OrderIt::value_type will be used in iterator arithmetic
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template < typename RAIt, typename OrderIt >
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struct permutation_iterator_generator
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{
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typedef boost::iterator_adaptor
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< RAIt,
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permutation_iterator_policies< OrderIt >
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> type;
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};
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template < class OrderIt, class RAIt >
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inline typename permutation_iterator_generator< RAIt, OrderIt >::type
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make_permutation_iterator(RAIt base, OrderIt order)
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{
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typedef typename permutation_iterator_generator< RAIt, OrderIt >::type result_t;
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return result_t( base, order );
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}
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} // namespace boost
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