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