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diff --git a/boost/statechart/result.hpp b/boost/statechart/result.hpp
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+++ b/boost/statechart/result.hpp
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+#ifndef BOOST_STATECHART_RESULT_HPP_INCLUDED
+#define BOOST_STATECHART_RESULT_HPP_INCLUDED
+//////////////////////////////////////////////////////////////////////////////
+// Copyright 2002-2010 Andreas Huber Doenni
+// Distributed under the Boost Software License, Version 1.0. (See accompany-
+// ing file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//////////////////////////////////////////////////////////////////////////////
+
+
+
+#include <boost/assert.hpp>
+
+
+
+namespace boost
+{
+namespace statechart
+{
+namespace detail
+{
+
+
+
+//////////////////////////////////////////////////////////////////////////////
+enum reaction_result
+{
+  no_reaction,
+  do_forward_event,
+  do_discard_event,
+  do_defer_event,
+  consumed
+};
+
+struct result_utility;
+
+//////////////////////////////////////////////////////////////////////////////
+class safe_reaction_result
+{
+  public:
+    //////////////////////////////////////////////////////////////////////////
+    safe_reaction_result( const safe_reaction_result & other ) :
+      reactionResult_( other.reactionResult_ )
+    {
+      // This assert fails when an attempt is made to make multiple copies of
+      // a result value. This makes little sense, given the requirement that
+      // an obtained result value must be returned out of the react function.
+      BOOST_ASSERT( reactionResult_ != consumed );
+      other.reactionResult_ = consumed;
+    }
+
+    ~safe_reaction_result()
+    {
+      // This assert fails when an obtained result value is not returned out
+      // of the react() function. This can happen if the user accidentally
+      // makes more than one call to reaction functions inside react() or
+      // accidentally makes one or more calls to reaction functions outside
+      // react()
+      BOOST_ASSERT( reactionResult_ == consumed );
+    }
+
+  private:
+    //////////////////////////////////////////////////////////////////////////
+    safe_reaction_result( reaction_result reactionResult ) :
+      reactionResult_( reactionResult )
+    {
+    }
+
+    operator reaction_result() const
+    {
+      const reaction_result val = reactionResult_;
+      reactionResult_ = consumed;
+      return val;
+    }
+
+    safe_reaction_result & operator=( const safe_reaction_result & );
+
+    mutable reaction_result reactionResult_;
+
+    friend struct result_utility;
+};
+
+
+
+} // namespace detail
+
+
+
+#ifdef NDEBUG
+  typedef detail::reaction_result result;
+#else
+  typedef detail::safe_reaction_result result;
+#endif
+
+
+namespace detail
+{
+
+
+
+//////////////////////////////////////////////////////////////////////////////
+struct result_utility
+{
+  static ::boost::statechart::result make_result( reaction_result value )
+  {
+    return value;
+  }
+
+  static reaction_result get_result( ::boost::statechart::result value )
+  {
+    return value;
+  }
+};
+
+
+
+} // namespace detail
+} // namespace statechart
+} // namespace boost
+
+
+
+#endif