The program has a few errors.
For example,
***** (define O ( X0 Y0 ))
should be something like
(define O (make-point X0 Y0))
(define O (point X0 Y0))
(define O (vector X0 Y0))
I'm not sure because the first two don't exist and I guess the last one is
not what you want, but you must change that line to
(define O (something X0 Y0))
***** (* cos dT 30)
I guess it should be (* (cos 30) dT)
but you have to transform the 30 degrees to radians.
----------
My suggestion is to try first with an easier exercise. Try to draw a
balloon that doesn't move. It's boring but the program is easier. Once you
understand all the details about the framework to draw the non moving
balloon, you can add the movement.
Gustavo
On Wed, Nov 16, 2016 at 6:54 AM, Masto Fine <[email protected]>
wrote:
> (define (ballon-tourne)
> (local [(define LARG 110 )
> (define HAUT 110 )
> (define SCENE (carre 100 100 'outline "black"))
> (define BALLON ( circle 5 'solid "red"))
> (define X0 (/ LARG 2))
> (define Y0 (/ HAUT 2 ))
> (define O ( X0 Y0 ))
> (define M ( XM YM ))
> (define P ((+ X0 30) Y0))
> (define t (angle OP OM ))
> (define INIT 0)
> (define dT 5)
> (define (suivant t)
> ((+ X0 (* cos dT 30)( - Y0 (* sin dT )))))
> (define (dessiner t)
> (place-image BALLON ( (+ X0 ( * cos t 30))(- Y0 (*sin t)))))
> (define (final? t)
> (= t 700))]
> (big-bang INIT
> (on-tick suivant)
> (on-draw dessiner)
> (stop-when final?))))can you correct me :
>
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