put tribonacci numbers out with the tail recursion algorithm.

tribonacci.scm

; put tribonacci numbers out with the tail recursion algorithm

(define (tribonacci n)
  (tribo-tail n 0 0 1))

(define (tribo-tail n a b c)
  (cond
    ((= n 0) or (= n 1) 0)
    ((= n 2) c)
    (else
     (let ((m (- n 1)))
       (tribo-tail m b c (+ a b c))))))
     
(display (tribonacci 100000))