On May 5, 2009, at 5:07 PM, Marijn Schouten (hkBst) wrote:

The function

(define (walk-f depth)
  (let step ((d 0) (x 0) (y 0) #;(z 0))
    (cond ((< d depth)
           (let ((d+1 (+ d 1)))
             (+
              (step d+1 (+ x 1) y)
              (+
               (step d+1 (- x 1) y)
               (+ (step d+1 x (+ y 1))
                       (step d+1 x (- y 1))) ))))
          (else
           (L2-norm x y)))))

calculates the total squared length.

Wouldn't this be simpler and more efficient:

  (define (walk-f n)
    (* n (expt 4 n)))

Aziz,,,

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