i have a scheme question

i have created a function called "repeat" that composes a function with itself n times. i have written it in two different ways. one works and the other doesn't. can you help me understand why the one doesn't work? tia.

the code:
https://gist.github.com/3134464

>>1

This is an ugly tail recursive version,


(define (repeat f n)
  (letrec ((loop (lambda (n accumulation)
                   (if (= n 0)
                     accumulation
                     (loop (- n 1) (compose f accumulation))))))
    (loop (- n 1) f)))

Repeated squaring:


(define (repeat f n)
  (cond ((= n 1) f)
        ((even? n) (repeat (compose f f) (/ n 2)))
        (else (compose f (repeat f (- n 1))))))