Extended next/prior using patch from Daniel Walker (Daniel.Walker-at-bowneglobal.com)

[SVN r21382]

include/boost/next_prior.hpp

@@ -8,9 +8,14 @@
 
 //  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
@@ -19,15 +24,30 @@ namespace boost {
 //  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