If you change (car a) to (superdupercar a), then (setf (superdupercar a) x) no longer works. You have to program the generalized place system of Common Lisp to

If you change (car a) to (superdupercar a), then (setf (superdupercar a) x) no longer works. You have to program the generalized place system of Common Lisp to recognize (superduper ...) as a place, and define what that means; then all is well. It could be as simple as (defsetf superdupercar superduperrplaca) If you have a function (superduperrplaca a x).