[CM] optional and default arguments in cm 3.8.0 scheme?

[Michael Winkler]

hi list

I'm struggling with optional and default arguments: How can I do this 
lisp code in schme common music?

(defun modl (list1 &optional (n 12))
   (loop for x in list1 collect (mod x n)))

examples:
(modl '(10 12 14))
 >> (10 0 2)
(modl '(10 12 14) 5)
 >> (0 2 4)

thankx and a happy new year
Michael