namespace boost { namespace fusion {

    struct random_access_traversal_tag;

    namespace result_of
    {
        template <typename Sequence, typename State, typename F>
        struct fold
            : fusion::detail::choose_fold<
            Sequence, State, F
            , is_base_of<random_access_traversal_tag, typename traits::category_of<Sequence>::type>::value>
        {};
    }
    
    template 
    inline typename result_of::fold::type
    fold(Sequence& seq, State const& state, F f)
...