;; find-cat : LOS -> Boolean
;; Is 'cat in los?
#;(define (find-cat los)
  (cond [(empty? los) false]
        [else (or (symbol=? (first los) 'cat)
                  (find-cat (rest los)))]))

;; find-dog : LOS -> Boolean
;; Is 'dog in los?
#;(define (find-dog los)
  (cond [(empty? los) false]
        [else (or (symbol=? (first los) 'dog)
                  (find-dog (rest los)))]))

;; find : Symbol LOS -> Boolean
;; Is s in los?
(define (find s los)
  (cond [(empty? los) false]
        [else (or (symbol=? (first los) s)
                  (find s (rest los)))]))

;; find-cat : LOS -> Boolean
;; Is 'cat in los?
(define (find-cat los)
  (find 'cat los))

(check-expect (find-cat (list 'dog 'elephant 'cat)) true)
(check-expect (find-cat (list 'dog 'elephant)) false)

;; find-dog : LOS -> Boolean
;; Is 'dog in los?
(define (find-dog los)
  (find 'dog los))

(check-expect (find-dog (list 'dog 'elephant 'cat)) true)
(check-expect (find-dog (list 'elephant)) false)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Parametric data definitions
;; 
;; A [Listof X is one of: 
;; - empty
;; - (cons X [Listof X])

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; sum : LON -> Number
;; compute sum of the numbers in the given list
#;(define (sum lon)
  (cond [(empty? lon) 0]
        [else (+ (first lon) 
                 (sum (rest lon)))]))

;; product : LON -> Number
;; compute product of the numbers in the given list
#;(define (product lon)
  (cond [(empty? lon) 1]
        [else (* (first lon) 
                 (product (rest lon)))]))


;; process : [X Y -> Y] Y [Listof X] -> Y
(define (process op base lox) 
  (cond [(empty? lox) base]
        [else (op (first lox) 
                  (process op base (rest lox)))]))

;; sum : LON -> Number
;; compute sum of the numbers in the given list
(define (sum lon)
  (process + 0 lon))
;; instantiating X = Number and Y = Number in signature of process

;; product : LON -> Number
;; compute product of the numbers in the given list
(define (product lon)
  (process * 1 lon))
;; instantiating X = Number and Y = Number in signature of process

(check-expect (sum (list 1 2 3)) 6)
(check-expect (product (list 2 2 3)) 12)


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; seg+scene : Posn Image -> Image
;; added a red segment at position p on top on given scene scn
(define (seg+scene p scn)
  (place-image (circle 5 'solid 'red)
               (posn-x p) (posn-y p)
               scn))

;; segs+scene : [Listof Posn] Image -> Image
#;(define (segs+scene lop scn)
  (cond [(empty? lop) scn]
        [else  (seg+scene (first lop) 
                        (segs+scene (rest lop) scn))]))

;; segs+scene : [Listof Posn] Image -> Image
(define (segs+scene lop scn)
  (process seg+scene scn lop))
;; instantiating X = Posn and Y = Image in signature of process
;; Note: process is built in; it is called foldr

               
(segs+scene (list (make-posn 10 10)
                  (make-posn 10 20)
                  (make-posn 20 20)) 
            (empty-scene 100 100))