;; IN: a vector, a function
;; OUT: 'okay
;; SideEffect: destructively applies function onto every element in the vector


(define (vector-map! fn vec)
  (define (loop n)
    (if (= n (vector-length vec))
	vec
	(begin
	  (vector-set! vec n (fn (vector-ref vec n)))
	  (loop (+ n 1)))))
  (loop 0))