;; ****************************************
;; *  Csu 211 : 2/11/2008
;; *  Lecture #14 Code
;; *  List abbreviations and Start of the "Worm" Game
;; ****************************************


;; List Abbreviations
;; * * * * * * * * * * * * *
(define list1 (cons 1 (cons 2 (cons 3 (cons 4 empty)))))
(define list2 (list 1 2 3 4))
(define list3 '(1 2 3 4))


(check-expect list1 list2)
(check-expect list2 list3)
(check-expect list1 list3)


;; Abbr. for accessors
;; * * * * * * * * * * * * *
(check-expect (first list1)  1)
(check-expect (rest list1)  '(2 3 4))

;; (second lst) => (first (rest lst))
(check-expect (second list1) 2)

;; (third lst) => (first (rest (rest lst)))
(check-expect (third list1)  3)

;; (fourth lst) => (first (rest (rest (rest lst))))
(check-expect (fourth list1) 4)

;; Local bindings/definitions
;; * * * * * * * * * * * * *
(define (f x)
  (* x x 5))

(define (r lst) (rest lst))

(define (list2string lst)
  (cond [(empty? lst) ""]
        [else 
         (local ((define r (list2string (rest lst)))
                 (define f (first lst))
                 (define f-str (cond [(string? f) f]
                                     [(number? f) (number->string f)]
                                     [else (error 'list2string
                                                  "Un-convertable type")])))
           (string-append f-str r))]))
          
(check-expect (f 3) 45)
(check-expect (r list1) '(2 3 4))
(check-expect (list2string (cons "Test: " list1)) "Test: 1234")

(generate-report)

;; *  Worm/Snake Game
;; ****************************************

;; ** LOP is either
;;      -- empty
;;      -- (cons Posn LOP)

;; ** Snake is a *non-empty* LOP

;; ** Dir is a Symbol that is either
;;      'up, 'down, 'left, or 'right

;; ** Food is a Posn

;; ** World is : (make-world Snake Dir Food)
(define-struct world (s d f))

(define a-snake (list (make-posn 200 200)
                      (make-posn 220 200)
                      (make-posn 240 200)
                      (make-posn 260 200)))

(define a-food (make-posn 100 100))

(define a-world (make-world a-snake 'up a-food))

(define EMPTY (empty-scene 400 400))
(define GRID 20)

;; draw-snake: Snake -> Scene
;; Draw a Snake (with a black head) into a Scene
(define (draw-snake snk)
  (local ((define p (first snk)))
    (place-image (circle (- (/ GRID 2) 2) 'solid 'black)
                 (posn-x p)
                 (posn-y p)
                 (draw-snk snk))))

;; draw-snk: Snake -> Scene
;; Draw a snake into a scene (no head...)
(define (draw-snk snk)
  (cond [(empty? snk) EMPTY]
        [(cons? snk) 
         (local ((define p (first snk)))
           (place-image (circle (/ GRID 2) 'solid 'red)
                        (posn-x p)
                        (posn-y p)
                        (draw-snk (rest snk))))]))

(draw-snake a-snake)