;; big-Theta of n, where n is the size of the input sentence

(define (member? wd sent)
  (if (empty? sent) #t
      (or (equal? wd (first sent))
	  (member? wd (butfirst sent)))))

;; big-Theta of (nm), where n is the size of the first input sentence
;; and m is the size of the second input sentence

(define (repeat? sent1 sent2)
  (cond ((empty? sent1) #f)
	((member? (first sent1) sent2) #t)
	(else (repeat? (bf sent1) sent2))))