My first Scheme program!

gistfile1.scm

(define (tabulate n f)
  (define (helper m)
    (if (= m n)
      ()
      (cons (f m) (helper (+ m 1)))))
  (helper 0))

(define (make-table x y fill)
  (define table (make-vector x))
  (tabulate x
    (lambda (i)
      (vector-set! table i (make-vector y fill))))
  table)

(define (table-ref table x y)
  (vector-ref (vector-ref table x) y))

(define (table-set! table x y obj)
  (define column (vector-ref table x))
  (vector-set! column y obj)
  obj)

(define (memoized-walk-count x y)
  (define table (make-table (+ x 1) (+ y 1) #f))
  (define (lookup x y)
    (define value (table-ref table x y))
    (if value
        value
        (table-set! table x y (walk-count x y))))
  (define (walk-count x y)
    (if (or (= x 0) (= y 0))
        1
        (+ (lookup (- x 1) y)
           (lookup x (- y 1)))))
  (walk-count x y))