;; File trfac.scm
;; Author: Robert Keller
;; Purpose: tail-recursive factorial using McCarthy's transformation

(load "tester.scm")

(define (fac n)
  (a 1 1 n))

(define (a i f n)
  (if (<= i n)
      (b i f n)
      (c i f n)))

(define (b i f n)
  (a (+ i 1) (* f i) n))

(define (c i f n)
  f)

(test (fac 4) 24)
(test (fac 5) 120)
(test (fac 10) 3628800)