General: DO NOT use 'list' as a variable name. It's perfectly valid, but it can be confused with 'list', the function. Try using lambda functions along with mapcar. I don't remember if we cover lambda functions, but here: http://grimpeur.tamu.edu/~colin/lp/node66.html is a good start. Here is an example of using mapcar with a lambda function: http://grimpeur.tamu.edu/~colin/lp/node69.html. Note, however, that in our version of lisp, the lambda function should be unquoted. Also note that lambda expressions still have access to variables in the scope of their outer functions. For example: (mapcar (setf y 3) (lambda (x) (+ x y)) '(4 7 2 9)) here the lambda has access to 'y'. In general, this tutorial is good: http://grimpeur.tamu.edu/~colin/lp/lp.html.