Suppose I write the following quasiquote expression: `(a ,X b ,Y) Is it equivalent to: (list 'a X 'b Y) or (cons 'a (cons X (cons 'b (cons Y '())))) [note: I assume here that list and cons have their initial binding]. The two expressions above are not equivalent if X and Y are arbitrary expressions because of call/cc. The R4RS doesn't say anything about this. Marc