;;;; section 2.2 ;;;;;;;
;;adam nelson
;;chet tobrey

(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 took saw liked)))

(defun one-of (set)
  "picks an element of a set, and makes a list of it."
  (list (random-elt set)))

(defun random-elt(choices)
  "Chooses and element randomly from a list"
  (elt choices (random (length choices))))
;;;;;

(egs :2.2
     (eg '(sentence)
         :of "the first generated sentence")
     (eg '(sentence)
         :of "sentence 2")
     (eg '(sentence)
         :of "sentence3")
     (eg '(sentence)
         :of "sentence 4")
     (eg '(noun-phrase)
         :of "a noun phrase")
     (eg '(verb-phrase)
         :of "a verb phrase" )
     (eg '(trace sentence noun-phrase verb-phrase article noun verb)
         :of "turning trace on")
     (eg '(sentence)
         :of "tracing the sentence function")
     (eg '(untrace)
         :of "untracing a sentence"))