"by stf ?? Tue May 06, 2014 11:22 pm Hi,i stuck on a problem, a kind of special flatten function :i want to input: '((a b c d e)((f g h)(i j k))(l m n o))) and output: => '((a b c d e) (f g h)(i j k)(l m n o))i can not find the solution for this problem and do not know lisp function who can do that..could you help me please ?thanksstf" . . . .