gistfile1.sls

;; simple
(define (fac acc n)
  (if (= n 1)
      acc
      (fac (* acc n) (- n 1))))

;; not
(define (fac n)
  (if (= n 1)
      1
      (* n (fac (- n 1)))))

;; both can be compiled with tail-call optimization.
;; first variant can be optimized more easily.