# [racket] why is the comparimng always false

 From: Roelof Wobben (r.wobben at home.nl) Date: Sat Jun 30 15:20:00 EDT 2012 Previous message: [racket] why is the comparimng always false Next message: [racket] why is the comparimng always false Messages sorted by: [date] [thread] [subject] [author]

```Op 30-6-2012 15:55, Matthias Felleisen schreef:
>
> On Jun 30, 2012, at 3:03 AM, Roelof Wobben wrote:
>
>> I can do the same for my problem.
>>
>> ; A Vanimal is one of :
>> ; - (make-Vcat ( x happiness)
>> ;   (make-Vcham ( x happiness)
>>
>> So Vanimal is not a struct but strictly a name.
>>
>> Am I on the right track.
>
>
> YES!
>

Oke,

Last problem I hope.

I have now this :

; niet grafische constanten.

(define move-animal 3)
(define move-gauge 0.1)

; grafische constanten

(define kat  .)
(define cham .)
(define gauge-omtrek (rectangle 1000 20 "outline" "black"))

; berekende constanten
(define correctie-cat ( / (image-width kat)2))
(define ondergrens-cat ( - 0  correctie-cat))
(define bovengrens-cat ( + breedte-werkblad correctie-cat))

(define correctie-cham ( / (image-width cham)2))
(define ondergrens-cham ( - 0  correctie-cham))
(define bovengrens-cham ( + breedte-werkblad correctie-cham))

; Te gebruiken structs

; Design a world program that works with both cats and chameleons:
; A VAnimal is either
; -- a VCat
; -- a VCham

(define-struct Vcat (Xcat Hcat Richting))
; Vcat = (make-editor Number Number)
; interp. (make-editor x h) where x is the x-coordinate of the cat and h
is the happiness of the cat.
; make-editor Number Number -> Vcat
; Vcat-Xcat Editor -> Number
; Vcat-Hcat Editor -> Number
; Vcat-Richting -> String
; Vcat? Editor Any -> Boolean

(define-struct Vcham (Xcham Hcham Richting))
; Vcham = (make-editor Number Number)
; interp. (make-editor x h) where x is the x-coordinate of the cham and
h is the happiness of the cham
; make-editor Number Number -> Vcat
; Vcham-Xcham Editor -> Number
; Vcham-Hcham Editor -> Number
; Vcham-Richting -> String
; Vcham? Editor Any -> Boolean

; Vcham -> Vcham
; Function who makes the image move to the left or turn to the right
(check-expect (links-of-draaien-cham (make-Vcham 20 100 "left"))
(make-Vcham 17 99.9 "left"))
(check-expect (links-of-draaien-cham (make-Vcham -39 100 "left"))
(make-Vcham -39 99.9 "right"))
(check-expect (links-of-draaien-cham (make-Vcham 1037 100 "left"))
(make-Vcham 1034 99.9 "left"))
(if ( < (Vcham-Xcham Vcham) ondergrens-cham)
(make-Vcham  (Vcham-Xcham s)  (- (Vcham-Hcham s) move-gauge) "right")
(make-Vcham (- (Vcham-Xcham s) move-animal) (- (Vcham-Hcham s)
move-gauge) "left")))

; Vcat -> Vcat
; Function who makes the image move to the left or turn to the right
(check-expect (links-of-draaien-cat (make-Vcat 20 100 "left"))
(make-Vcat 17 99.9 "left"))
(check-expect (links-of-draaien-cat (make-Vcat -39 100 "left"))
(make-Vcat -39 99.9 "right"))
(check-expect (links-of-draaien-cat (make-Vcat 1037 100 "left"))
(make-Vcat 1034 99.9 "left"))
(if ( < (Vcat-Xcat Vcat) ondergrens-cat)
(make-Vcat  (Vcat-Xcat s)  (- (Vcat-Hcat s) move-gauge) "right")
(make-Vcat (- (Vcat-Xcat s) move-animal) (- (Vcat-Hcat s)
move-gauge) "left"))
)

; Vcham -> Vcham
; Function who makes the image move to the right or turn to the left
(check-expect (rechts-of-draaien-cham (make-Vcham 20 100 "right"))
(make-Vcham 23 99.9 "right"))
(check-expect (rechts-of-draaien-cham (make-Vcham -39 100 "right"))
(make-Vcham -36 99.9 "right"))
(check-expect (rechts-of-draaien-cham (make-Vcham 1040 100 "right"))
(make-Vcham 1040 99.9 "left"))
(define (rechts-of-draaien-cham s)
(if ( > (Vcham-Xcham Vcham) bovengrens-cham)
(make-Vcham  (Vcham-Xcham s)  (- (Vcham-Hcham s) move-gauge) "left")
(make-Vcham (+ (Vcham-Xcham s) move-animal) (- (Vcham-Hcham s)
move-gauge) "right")))

; Vcat -> Vcat
; Function who makes the image move to the right or turn to the left
(check-expect (rechts-of-draaien-cat (make-Vcat 20 100 "right"))
(make-Vcat 23 99.9 "right"))
(check-expect (rechts-of-draaien-cat (make-Vcat -39 100 "right"))
(make-Vcat -36 99.9 "right"))
(check-expect (rechts-of-draaien-cat (make-Vcat 1040 100 "right"))
(make-Vcat 1040 99.9 "left"))
(define (rechts-of-draaien-cat s)
(if ( > (Vcat-Xcat Vcat) bovengrens-cat)
(make-Vcat  (Vcat-Xcat s)  (- (Vcat-Hcat s) move-gauge) "left")
(make-Vcat (+ (Vcat-Xcat s) move-animal) (- (Vcat-Hcat s)
move-gauge) "right"))
)

; Vanimal -> Vanimal
; Function which change the world on clock ticks.
; On every tick the X-coordinate changes 3 pixels and the happiness
decrease with 0.1.
(define (tock s)
(cond
[(Vcat? s)(if(equal? (Vcat-Richting s) "left")
[(Vcham? s) (if(equal? (Vcham-Richting s) "left")
))

; Vanimal -> Image
; Function who display the state of the world into a image.
(check-expect (render (make-Vcat 90 100 "left")) (place-image
(overlay/xy gauge-omtrek 0 0 (rectangle 1000 20 "solid" "red")) 500 10
(place-image kat 90 140 workspace)))
(check-expect (render (make-Vcat 0 100 "right"))   (place-image
(overlay/xy gauge-omtrek 0 0 (rectangle 1000 20 "solid" "red")) 500 10
(place-image kat 0 140 workspace)))
(check-expect (render (make-Vcham 90 100 "left")) (place-image
(overlay/xy gauge-omtrek 0 0 (rectangle 1000 20 "solid" "red")) 500 10
(place-image cham 90 140 workspace)))
(check-expect (render (make-Vcham 0 100 "right"))   (place-image
(overlay/xy gauge-omtrek 0 0 (rectangle 1000 20 "solid" "red")) 500 10
(place-image cham 0 140 workspace)))
(define (render s)
[cond
[(Vcat? s)   (place-image (overlay/xy gauge-omtrek 0 0 (rectangle
(* 10 (Vcat-Hcat s)) 20 "solid" "red")) 500 10 (place-image kat
(Vcat-Xcat s) 140 workspace))]
[ (Vcham? s) (place-image (overlay/xy gauge-omtrek 0 0 (rectangle
(* 10 (Vcham-Hcham s)) 20 "solid" "red")) 500 10 (place-image cham
(Vcham-Xcham s) 140 workspace))]
])

; VCat keyevent -> Vcat
; Function who changes the world on a key-event
(check-expect (happy-cat (make-Vcat 90 10 "right")"up") (make-Vcat 90 12
"right"))
(check-expect (happy-cat (make-Vcat 90 100 "left")"down") (make-Vcat 90
100 "left"))
(define (happy-cat Vcat k)
(cond
[ (and (key=? k "up") (< (Vcat-Hcat Vcat) 100))   (make-Vcat
(Vcat-Xcat Vcat) (+ (Vcat-Hcat Vcat)2) (Vcat-Richting Vcat))]
[ (and (key=? k "down") (< (Vcat-Hcat Vcat) 100)) (make-Vcat
(Vcat-Xcat Vcat) (+ (Vcat-Hcat Vcat)5) (Vcat-Richting Vcat))]
[else Vcat]
))

; VCham keyevent -> Vcat
; Function who changes the world on a key-event
(check-expect (happy-cham (make-Vcham 90 10 "right")"up") (make-Vcham 90
12 "right"))
(check-expect (happy-cham (make-Vcham 90 100 "left")"down") (make-Vcham
90 100 "left"))
(define (happy-cham Vcham k)
(cond
[ (and (key=? k "up") (< (Vcat-Hcat Vcat) 100))   (make-Vcat
(Vcat-Xcat Vcat) (+ (Vcat-Hcat Vcat)2) (Vcat-Richting Vcat))]
[else Vcat]
))

(define (happy s k)
(cond
[ (Vcat? s) (happy-cat s k)]
[ (Vcham? s) (happy-cham s k)]
))

(define (stop s)
(cond
[ (Vcat? s) (equal? (Vcat-Hcat s) 0)]
[  (Vcham? s) (equal? (Vcham-Hcham s) 0)]
))

(define (main s)
(cond
[(Vcat? s) (big-bang s (check-with Vcat?) (on-tick tock) (on-draw
render) )]
[(Vcham? s) (big-bang s (check-with Vcham?) (on-tick tock) (on-draw
render) )]
))

(main (make-Vcat 12 100 "left"))

But it fails with this :

Vcat-Xcat: expects a Vcat; given (make-signature ...)
Vcham-Xcham: expects a Vcham; given (make-signature ...)

Can it be a problem that on both I call the structure s ?

Roelof

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