Hi ,All I'm new to lisp, using GNU Clisp. I have a problem when I do some Lisp programming training. For example, for the list (a (b1 b2) c (d1 d2) (e1 e2 e3) f), I need a function to return all the possible combinations like: ((a b1 c d1 e1 f) (a b1 c d1 e2 f) (a b1 c d1 e3 f) (a b1 c d2 e1 f) (a b1 c d2 e2 f) (a b1 c d2 e3 f) (a b2 c d1 e1 f) (a b2 c d1 e2 f) (a b2 c d1 e3 f) (a b2 c d2 e1 f) (a b2 c d2 e2 f) (a b2 c d2 e3 f)) My tries trended to be unsuccessful. Is it too easy to ask this here? If so, where is the forum for people like me? best regards, XIE Wensheng