Incomplete work for using Boost.Polygon to compute medial axis

xs/src/boost/next_prior.hpp

@@ -0,0 +1,51 @@
+//  Boost next_prior.hpp header file  ---------------------------------------//
+
+//  (C) Copyright Dave Abrahams and Daniel Walker 1999-2003. Distributed under the Boost
+//  Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  See http://www.boost.org/libs/utility for documentation.
+
+//  Revision History
+//  13 Dec 2003  Added next(x, n) and prior(x, n) (Daniel Walker)
+
+#ifndef BOOST_NEXT_PRIOR_HPP_INCLUDED
+#define BOOST_NEXT_PRIOR_HPP_INCLUDED
+
+#include <iterator>
+
+namespace boost {
+
+//  Helper functions for classes like bidirectional iterators not supporting
+//  operator+ and operator-
+//
+//  Usage:
+//    const std::list<T>::iterator p = get_some_iterator();
+//    const std::list<T>::iterator prev = boost::prior(p);
+//    const std::list<T>::iterator next = boost::next(prev, 2);
+
+//  Contributed by Dave Abrahams
+
+template <class T>
+inline T next(T x) { return ++x; }
+
+template <class T, class Distance>
+inline T next(T x, Distance n)
+{
+    std::advance(x, n);
+    return x;
+}
+
+template <class T>
+inline T prior(T x) { return --x; }
+
+template <class T, class Distance>
+inline T prior(T x, Distance n)
+{
+    std::advance(x, -n);
+    return x;
+}
+
+} // namespace boost
+
+#endif  // BOOST_NEXT_PRIOR_HPP_INCLUDED