From 8a4839354e8f34259531882945bf0f466bcecfeb Mon Sep 17 00:00:00 2001
From: Toon Knapen <toon.knapen@gmail.com>
Date: Fri, 30 Nov 2001 10:38:36 +0000
Subject: [PATCH] permutation_iterator_adaptor and generator

[SVN r11823]
---
 include/boost/permutation_iterator.hpp | 71 ++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 include/boost/permutation_iterator.hpp

diff --git a/include/boost/permutation_iterator.hpp b/include/boost/permutation_iterator.hpp
new file mode 100644
index 0000000..7c05cab
--- /dev/null
+++ b/include/boost/permutation_iterator.hpp
@@ -0,0 +1,71 @@
+// (C) Copyright Toon Knapen 2001. Permission to copy, use,
+// modify, sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+//
+
+#include <boost/iterator_adaptors.hpp>
+
+namespace boost {
+
+  template < typename OrderIt >
+  struct permutation_iterator_policies : public default_iterator_policies
+  {
+    permutation_iterator_policies() {}
+
+    permutation_iterator_policies(OrderIt order_it) 
+      : order_it_( order_it ) 
+    {}
+
+    template <class IteratorAdaptor>
+    typename IteratorAdaptor::reference dereference(const IteratorAdaptor& x) const
+    { return *(x.base() + *order_it_); }
+
+    template <class IteratorAdaptor>
+    void increment(IteratorAdaptor& x)
+    { ++order_it_; }
+
+    template <class IteratorAdaptor>
+    void decrement(IteratorAdaptor& x)
+    { --order_it_; }
+
+    template <class IteratorAdaptor, class DifferenceType>
+    void advance(IteratorAdaptor& x, DifferenceType n)
+    { std::advance( order_it_, n ); }
+
+    template <class IteratorAdaptor1, class IteratorAdaptor2>
+    typename IteratorAdaptor1::difference_type
+    distance(const IteratorAdaptor1& x, const IteratorAdaptor2& y) const
+    { return std::distance( x.policies().order_it_, y.policies().order_it_ ); }
+
+    template <class IteratorAdaptor1, class IteratorAdaptor2>
+    bool equal(const IteratorAdaptor1& x, const IteratorAdaptor2& y) const
+    { return x.policies().order_it_ == y.policies().order_it_; }
+  
+    OrderIt order_it_;
+  };
+
+  /// generate an iterator that will access the elements
+  /// behind the random-access iterator RAIt in the
+  /// order specified by the OrderIt iterator.
+  /// preconditions:
+  /// The OrderIt::value_type will be used in iterator arithmetic
+  template < typename RAIt, typename OrderIt >
+  struct permutation_iterator_generator
+  {
+    typedef boost::iterator_adaptor
+    < RAIt,
+      permutation_iterator_policies< OrderIt > 
+    > type;
+  };
+
+  template < class OrderIt, class RAIt >
+  inline typename permutation_iterator_generator< RAIt, OrderIt >::type
+  make_permutation_iterator(RAIt base, OrderIt order)
+  {
+    typedef typename permutation_iterator_generator< RAIt, OrderIt >::type result_t;
+    return result_t( base, order );
+  }
+
+} // namespace boost