Thanks, that worked now. I like the fusion::for_each loop, it's very handy! Anyway, when I started this thread I actually had something else in my mind. As you can see the doSomething() is templated. I would like to create a type vector depending on the template parameter, here S. Is that possible? I could image to have something like this ( beware bad pseudo code ): template <class S> void doSomething( S& s ) { //create vector depending on S's length typedef fusion::vector<S::num_values> vec; // vector length // add the members type to vec fusion::for_each_member( s, vec.add() ); // create boost tuple type out of vec fusion::make_tuple( vec ); } Am I totally fantasying here? I think all the infomation are available at compile time. Thanks again, Christian