;; A person is (make-person string number symbol list-of-person)
(define-struct person (name year eye kids))

;; A list-of-person is
;; - empty, or
;; - (cons person list-of-person)


;; people-with-kids : person -> list-of-string
;; consumes a person and produces list of names of all people in their family
;;   tree who have children
(define (people-with-kids aper)
  (cond [(cons? (person-kids aper))
	 (cons (person-name aper) (kids-with-kids (person-kids aper)))]
	[else empty]))

;; kids-with-kids : list-of-person -> list-of-string
;; consumes list of people and produces names of all descendents of those people 
;;   who have children
(define (kids-with-kids alop)
  (cond [(empty? alop) empty]
	[(cons? alop) (append (people-with-kids (first alop))
			      (kids-with-kids (rest alop)))]))

;;--------------------------------------------------------------------


;; find-person : string person -> person OR false
;; consumes name and person and produces person with given name, or
;;   false if person not in tree 
(define (find-person name aper) 
  (cond [(string=? (person-name aper) name) aper]
        [else (find-in-list name (person-kids aper))]))

;; find-in-kids : string list-of-person -> person OR false
;; consume name and list of person and returns person with given name
;;  from trees in the list or false if no such person
(define (find-in-kids name alop)
  (cond [(empty? alop) false]
        [(cons? alop) (cond [(person? (find-person name (first alop)))
	                     (find-person name (first alop))]
                            [else (find-in-kids name (rest alop))])]))

;;--------------------------------------------------------------------