; A snake is
;  (make-snake sym num sym)
(define-struct snake (name weight food))

;; Example snake:
(make-snake 'slinky 12 'rats)
;; Example uses of the selectors
(snake-name (make-snake 'slinky 12 'rats))
(snake-weight (make-snake 'slinky 12 'rats))
(snake-food (make-snake 'slinky 12 'rats))

;; Example abbreviation (but avoiding abbreviations
;;  until you feel like you really understand what's
;;  going on)
(define Slinky (make-snake 'slinky 12 'rats))

;; ----------------------------------------
;; Implement snake-skinny?

;; Data step is done above

;; snake-skinny? : snake -> bool
;;  Returns true if s is less than 10 lbs, false
;;  otherwise
;(define (snake-skinny? s)
;  ... (snake-name s)
;      (snake-weight s)
;      (snake-food s) ...)
(define (snake-skinny? s)
  (< (snake-weight s) 10))
(snake-skinny? (make-snake 'slinky 12 'rats))
"should be" false
(snake-skinny? (make-snake 'slimey 5 'grass))
"should be" true
(snake-skinny? (make-snake 'suzie 10 'people))
"should be" false

;; ----------------------------------------
;; Implement feed-snake

;; Data step is done above

; feed-snake : snake -> snake
;  To feed s five pounds
;(define (feed-snake s)
;  ... (snake-name s)
;      (snake-weight s)
;      (snake-food s) ...)
(define (feed-snake s)
  (make-snake (snake-name s)
              (+ 5 (snake-weight s))
              (snake-food s)))
(feed-snake (make-snake 'slinky 12 'rats))
"should be" (make-snake 'slinky 17 'rats)

;; ----------------------------------------
;; Implement run-over-with-car

; A dillo is
;   (make-dillo num bool)
(define-struct dillo (weight alive?))

;; Example:
(make-dillo 3 true)
(make-dillo 2 false)

; run-over-with-car : dillo -> dillo
;  To kill dillo d (accidentally)
;(define (run-over-with-car d)
;  ...  (dillo-weight d)
;       (dillo-alive? d) ...)
(define (run-over-with-car d)
  (make-dillo (dillo-weight d)
              false))
(run-over-with-car (make-dillo 3 true))
"should be" (make-dillo 3 false)
(run-over-with-car (make-dillo 2 false))
"should be" (make-dillo 2 false)

;; ----------------------------------------
;; Implement feed-dillo
;;  This one is almost like feed-snake,
;;  except for the twist about dead dillos.
;;  It makes sense, then, to implement a
;;  simple dillo feeder, force-feed-dillo,
;;  and then handle the extra twist in a
;;  separate function (i.e., break up the
;;  problem into smaller pieces even before
;;  applying the recipe)

; force-feed-dillo : dillo -> dillo
;  Feeds d 2 lbs of food
;(define (force-feed-dillo d)
;  ... (dillo-weight d)
;      (dillo-alive? d) ...)
(define (force-feed-dillo d)
  (make-dillo (+ 2 (dillo-weight d))
              (dillo-alive? d)))
(force-feed-dillo (make-dillo 2 true))
"should be" (make-dillo 4 true)
(force-feed-dillo (make-dillo 1 false))
"should be" (make-dillo 3 false)

; feed-dillo : dillo -> dillo
;; feed d 2 lbs if d is alive
;(define (feed-dillo d)
;  ... (dillo-weight d)
;      (dillo-alive? d) ...)
(define (feed-dillo d)
  (cond
    [(dillo-alive? d) (force-feed-dillo d)]
    [else  d]))
(feed-dillo (make-dillo 2 true))
"should be" (make-dillo 4 true)
(feed-dillo (make-dillo 1 false))
"should be" (make-dillo 1 false)