[Fluxus] Fluxus Digest, Vol 70, Issue 13

[gabor papp]

hi Eduardo,

> I can take those values of "vel" to scale some objects (for example), but in
> some time it sends me an error in task, because expects type<vector>  and
> given " #f ", or in other examples expects procedure and given the same " #f
> "; this #f value appears when no midi message it's sending from the device.
#f means false, you can use a conditional expression for testing, 
something like:

(define (mid)
        (define note (midi-note))
        (define vel (vector-ref note 3))
        (when vel
             (displayln vel)))

i suggest that you should read the fluxus manual and the racket 
documentaion to have a better grasp of the basics of the language.

http://en.flossmanuals.net/Fluxus/Introduction
http://docs.racket-lang.org/guide/index.html
http://www.htdp.org/

best,
gabor