(define (make-grid grid-width grid-height)
  (list grid-width (make-vector (* grid-width grid-height))))

(define (grid-width g)
  (car g))

(define (grid-height g)
  (/ (vector-length (cadr g)) (car g)))

(define (grid-ref g i j)
  (vector-ref (cadr g) (+(* j (grid-width g))i)))

(define (grid-set! g i j x)
  (vector-set! (cadr g) (+(* j (grid-width g))i) x))


 (define foobar (make-grid 4 3))
 (display (grid-width foobar)) (newline)
 (display (grid-height foobar))(newline)
 (display (grid-ref foobar 2 1 ))(newline)
 (grid-set! foobar 2 1 5)
 (display (grid-ref foobar 2 1 ))(newline)