[racket] structures question

On 3/29/12 10:20 AM, Roelof Wobben wrote:
>
> ;; 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)
>   ( + (pos-y posmanhetten) (pos-x manhetten)))

You have several small problems in this program:

1) You use of parentheses in the test cases are wrong.
2) Several variables are misspelled, such as pos-x (should be posn-x), 
posmanhetten (should be pos-manhatten), manhetten (should be 
pos-manhatten), etc.

Fixing those problems fixes the program:

;; 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)))


[Also: "Manhattan" is the proper spelling.]

David