;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-intermediate-reader.ss" "lang")((modname 18.1.10) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp")))))
;A parent structure is
;(make-parent children name date eyes)
;where name and eyes are symbols,
;date is a number, and children is a
;list-of-children.

(define-struct parent (children name date eyes))
;
;A list-of-children is either
;1. an empty list or
;2. (cons p loc) where p is a parent
;and loc is a list-of-children.

;fun-for-parent: parent -> ???
;Template
;(define (fun-for-parent a-parent)
;  ... (parent-children a-parent) ...
;  ... (parent-name a-parent) ...
;  ... (parent-date a-parent) ...
;  ... (parent-eyes a-parent) ...)

;
;fun-for-loc : list-of-children -> ???
;(define (fun-for-loc a-loc)
;  (cond
;    [(empty? a-loc) ...]
;    [else ... (first a-loc) ...
;          ... (fun-for-loc (rest a-loc)) ...]))


;Third Generation
(define Gustav (make-parent empty 'Gustav 1988 'brown))

;Second Generation
(define Fred (make-parent (list Gustav) 'Fred 1966 'pink))
(define Eva (make-parent (list Gustav) 'Eva 1965 'blue))
(define Dave (make-parent empty 'Dave 1955 'black))
(define Adam (make-parent empty 'Adam 1950 'yellow))

;First Generation
(define Bettina (make-parent (list Adam Dave Eva) 'Bettina 1926 'green))
(define Carl (make-parent (list Adam Dave Eva) 'Carl 1926 'green))

;Test - All should return true
;(blue-eyed-descendant? Bettina)
;(blue-eyed-descendant? Eva)
;(not (blue-eyed-descendant? Gustav))
;(not (blue-eyed-descendant? Adam))

;blue-eyed-descendant? : parent -> boolean
;Given a-parent, determines whether the parent
;or any of its descendants have blue eyes.

;blue-eyed-children? : list-of-children -> boolean
;Given a-loc (list-of-children), return true if
;any parent structure within the list-of-children have blue eyes
;or if any of their descendants have blue eyes.

(define (blue-eyed-descendant a-parent)
  (local ((define (blue-eyed-descendant? a-parent)
            (cond
              [(symbol=? (parent-eyes a-parent) 'blue) true]
              [else (blue-eyed-children? (parent-children a-parent))]))
          
          (define (blue-eyed-children? a-loc)
            (cond
              [(empty? a-loc) false]
              [else (or (blue-eyed-descendant? (first a-loc))
                        (blue-eyed-children? (rest a-loc)))])))
    (blue-eyed-descendant a-parent)))