Hi, I am trying to apply fusion::for_each on a sequence, but inside the unary functor applied to each element, I need to know the index of the element in question, because I need to extract elements with the same index from other sequences. fusion::vector<...> fseq1; fusion::vector<...> fseq2; fusion::vector<...> fseq3; fusion::vector<...> fseq4; fusion::for_each( fseq1, functor<...>(fseq2, fseq3, fseq4) ); template <typename Seq2, typename Seq3, typename Seq4) struct functor { /// ctor template <typename T> void operator()( const T& t) const { /// find out index of t in fseq1, /// use elements from fseq2,3,4 at the same index } }; I could use boost::fusion::find to get an iterator and then get its index, but this doesn not look clean, Any ideas, Rds,