;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-abbr-reader.ss" "lang")((modname week3_f_full) (read-case-sensitive #t) (teachpacks ((lib "image.ss" "teachpack" "2htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "image.ss" "teachpack" "2htdp")))))
; A ftn is either
  ; - empty
  ; - (make-child symbol number symbol ftn ftn)
(define-struct child (name date eyes mom dad))
; template:
; (define (fun-for-ftn f)
;     (cond [(empty? f) ...]
;           [else ...(child-name f)
;                 ...(child-date f)
;                 ...(child-eyes f)
;                 ...(fun-for-ftn (child-mom f))
;                 ...(fun-for-ftn (child-dad f)) ]))

(define mary (make-child 'mary 1926 'brown empty empty))
(define peter (make-child 'peter 1926 'blue empty empty))
(define sarah (make-child 'sarah 1965 'green mary peter))
(define orville (make-child 'orville 1966 'orange empty empty))
(define gustav (make-child 'gustav 1990 'blue sarah orville))

; blue-eyed-ancestor? : ftn -> boolean
; determines if there is a blue-eyed person in family tree
(define (blue-eyed-ancestor? f) 
       (cond [(empty? f) false]
           [else (or (symbol=? 'blue (child-eyes f))
                    (blue-eyed-ancestor? (child-mom f))
                    (blue-eyed-ancestor? (child-dad f))) ]))

(check-expect (blue-eyed-ancestor? sarah) true)
(check-expect (blue-eyed-ancestor? orville) false)

; template:
;; fun-for-ftn : ftn  ->  ???
; (define (fun-for-ftn a-ftree)
;  (cond
;    [(empty? a-ftree) ...]
;    [else
;      ... (child-name a-ftree) ...
;      ... (child-date a-ftree) ...
;      ... (child-eyes a-ftree) ...
;      ... (fun-for-ftn (child-dad a-ftree)) ...
;      ... (fun-for-ftn (child-mom a-ftree)) ...
;]))

; -- remember to think about remove and append for homework #3....