;; 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-reader.ss" "lang")((modname week2_w_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")))))
; max-part : posn -> number
; to return the maximum coordinate of the posn
; template:
;  ...(posn-x p)...
;  ...(posn-y p)...
(define (max-part p) 
  (max (posn-x p) (posn-y p)
  ))

(check-expect (max-part (make-posn 2 3)) 3)
(check-expect (max-part (make-posn -1 -4)) -1)




; Data definition:
; a snake is:
; - (make-snake symbol number symbol)
(define-struct snake (name weight food))  
; syntax: struct name, fields names

;Creates four functions:
; (make-snake a b c)
; (snake-name s)
; (snake-weight s)
; (snake-food s)
; (snake? s)


; skinny-snake?: snake -> boolean
; returns true if snake is less than 10lbs, false otherwise
; ...(snake-name s)...
; ...(snake-weight s)...
; ...(snake-food s)...
(define (skinny-snake? s) 
(< (snake-weight s) 10)
  )

(check-expect (skinny-snake? (make-snake 'bob 13 'mice)) false)
(check-expect (skinny-snake? (make-snake 'jill 9 'mice)) true)


; feed-snake : snake -> snake
; feeds the snake a 5lb meal
(define (feed-snake s)
  (make-snake 
   (snake-name s)
   (+ 5 (snake-weight s))
   (snake-food s)
  ))

(check-expect (feed-snake (make-snake 'tim 4 'rat)) (make-snake 'tim 9 'rat))
(check-expect (feed-snake (make-snake 'jill 9 'mouse)) (make-snake 'jill 14 'mouse))

; a dillo is
; (make-dillo number boolean)
(define-struct dillo (weight dead?))
;template:
; ...(dillo-weight d)
; ...(dillo-dead? d)

; feed-dillo : dillo -> dillo
; feeds a dillo a 2lb meal
(define (feed-dillo d) 
  (make-dillo
  (cond [(dillo-dead? d) (dillo-weight d)]
        [else (+ 2 (dillo-weight d))])
  (dillo-dead? d)
  ))

(check-expect (feed-dillo (make-dillo 12 false)) (make-dillo 14 false))
(check-expect (feed-dillo (make-dillo 11 true)) (make-dillo 11 true))

; an ant is
; - (make-ant number posn)
(define-struct ant (weight loc))
;template:
;...(ant-weight a)
;...(ant-loc a)

(define ant1 (make-ant 0.01 (make-posn 0 0)))
(define ant2 (make-ant 0.005 (make-posn 2 3)))

; ant-at-home? : ant -> boolean
; returns whether ant is at home (the origin)
(define (ant-at-home? a) 
  (at-zero? (ant-loc a))
  )

(check-expect (ant-at-home? ant1) true)
(check-expect (ant-at-home? ant2) false)

; at-zero? : posn -> boolean
; returns whether posn is origin
(define (at-zero? p) 
 (and 
  (= 0 (posn-x p))
  (= 0 (posn-y p))
  )
 )

(check-expect (at-zero? (make-posn 0 1)) false)
(check-expect (at-zero? (make-posn 0 0)) true)

; feed-ant : ant -> ant
; feeds ant a 0.01lb meal
(define (feed-ant a) 
  (make-ant (+ (ant-weight a) 0.01)
   (ant-loc a))
  )

(check-expect (feed-ant ant1) (make-ant 0.02 (make-posn 0 0)))

; An animal is either:
;  - snake, or
;  - dillo, or
;  - ant
; Template:
; (cond [(snake? a) ...]
;       [(dillo? a) ...]
;       [(ant? a) ...]
; )

;Example:
(make-snake 'bob 10 'fries)

;feed-animal : animal -> animal
; feeds the animal appropriate-sized meal
(define (feed-animal a) 
 (cond [(snake? a) (feed-snake a)]
       [(dillo? a) (feed-dillo a)]
       [(ant? a) (feed-ant a)]
 )
  )

(check-expect (feed-animal ant1) (make-ant 0.02 (make-posn 0 0)))
(check-expect (feed-animal (make-snake 'tim 4 'rat)) (make-snake 'tim 9 'rat))
(check-expect (feed-animal (make-dillo 11 true)) (make-dillo 11 true))

;a dongwu is either:
; (make-snake symbol number symbol), or
; (make-dillo number boolean),
; (make-ant number (make-posn number number))

; (cond [(snake? d) ...(snake-name d)...(snake-weight d)...(snake-food d)]
;       [(dillo? d) ...(dillo-weight d)...(dillo-dead? d)]
;       [(ant? d) ...(ant-weight d)...(ant-loc d)])