[racket] structures question

Op 29-3-2012 16:37, David Van Horn schreef:
> ;; Posn -> Number.
> ;; A programm for calculating the distance is Manhatten
> (check-expect (manhatten (make-posn 7 3 )) 10)
> (check-expect (manhatten (make-posn 1 1 )) 2)
>
> (define (manhatten pos-manhatten)
>  (+ (posn-y pos-manhatten) (posn-x pos-manhatten))) 

Thanks,

Learning point : To take nire care about the ().

Roelof