(defun sentence () 
  (append (noun-phrase) (verb-phrase)))
(defun noun-phrase ()
  (append (article) (noun)))
(defun verb-phrase ()
  (append (verb) (noun-phrase)))
(defun article ()
  (one-of '(the a)))
(defun noun ()
  (one-of '(man ball woman table)))
(defun verb ()
  (one-of '(hit look saw liked)))

(defun one-of (set)
  "Pick one element of set, and make a list of it."
  (list (random-elt set)))
(defun random-elt (choice)
  "Choose an element for a list at random."
  (elt choice (random (length choice))))