That's why you actually won't find many instances of such patterns in practice. Either you refactor to have structures/classes, or you define your own accessors

That's why you actually won't find many instances of such patterns in practice. Either you refactor to have structures/classes, or you define your own accessors. Besides, if you are using CL, FIRST, SECOND, THIRD, ... , TENTH, NTH and REST are defined by the spec (http://clhs.lisp.se/Body/f_firstc.htm http://clhs.lisp.se/Body/f_firstc.htm).