;; the book example Ch. 14

;; a child structure represents a person
;; father and mother are "child" structures that 
;; represent the person's parents
;; or empty if there is no data on a parent
;; name is a symbol (the person's name)
;; date is a positive integer (year of birth)
;; eyes is a symbol that represents the color of the eyes
(define-struct child (father mother name date eyes))

;; Oldest Generation:
(define Carl (make-child empty empty 'Carl 1926 'green))
(define Bettina (make-child empty empty 'Bettina 1926 'green))

;; Middle Generation:
(define Adam (make-child Carl Bettina 'Adam 1950 'yellow))
(define Dave (make-child Carl Bettina 'Dave 1955 'black))
(define Eva (make-child Carl Bettina 'Eva 1965 'blue))
(define Fred (make-child empty empty 'Fred 1966 'pink))

;; Youngest Generation: 
(define Gustav (make-child Fred Eva 'Gustav 1988 'brown))

;; blue-eyed-ancestor? : family tree node (ftn)  ->  boolean
;; to determine whether a-ftree contains a child
;; structure with 'blue in the eyes field
(define (blue-eyed-ancestor? a-ftree)
  (cond
    ;; fill in the rest 
    ))

(check-expect (blue-eyed-ancestor? Carl) false)
(check-expect (blue-eyed-ancestor? Gustav) true)

;; count-persons: family tree node -> integer
;; consumes a family tree node
;; counts how many people are there in the known family tree
;; rooted in the node, counting the person at the node itself


(check-expect (count-persons Adam) 3)
(check-expect (count-persons Gustav) 5)


;; eye-colors: family tree node -> list of symbols
;; consumes a family tree node and produces a list of all eye colors 
;; in the tree. An eye color may occur more than once in the list.


;; note that check-expect may need to be adjusted if the list elements 
;; are the same but in a different order
(check-expect (eye-colors Adam) (list 'yellow 'green 'green))
(check-expect (eye-colors Gustav) (list 'brown 'blue 'green 'green 'pink))