$ txr -e "(progn
  (defun fs (fun seq) (mapcar fun seq))
  (defun f1 (num) (* 2 num))
  (defun f2 (num) (* num num))
  (defvar fsf1 (op fs f1))  ;; pointless: can just be (defun fsf1 (seq) (fs f1 seq)) !!!
  (defvar fsf2 (op fs f2))

  (print [fs fsf1 '((0 1 2 3) (2 4 6 8))]) (put-line \"\")
  (print [fs fsf2 '((0 1 2 3) (2 4 6 8))]) (put-line \"\"))"
((0 2 4 6) (4 8 12 16))
((0 1 4 9) (4 16 36 64))