Factorial 3 ways

factorial.scm

;; factorial (recursive)
(define fact
  (lambda (n)
    (if (= n 0)
        1
        (* n (fact (- n 1))))))

(display (fact 5)) ;; => 120
(newline)

;; factorial (iterative)
(define facti
  (lambda (x i)
    (if (= x 0)
        i
        (facti (- x 1) (* x i)))))

(display (facti 5 1)) ;; => 120
(newline)  

;; factorial (continuation passing style)
(define factc 
  (lambda (n c)
    (if (= n 0)
        (c 1)
        (factc (- n 1)
               (lambda (a) (c (* n a)))))))


(display (factc 5 (lambda (x) x))) ;; => 120
(newline)