//  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