Dan's Thoughts Thinking somewhat carefully

(define (reverse sequence)
  (fold-right (lambda (x y) <??>) nil sequence))
(define (reverse sequence)
  (fold-left (lambda (x y) <??>) nil sequence))

(define (fold-right fn init-value items)
  (if (null? items)
    init-value
    (fn (car items)
        (fold-right fn init-value (cdr items)))))
 
(define (fold-left op initial sequence)
  (define (iter result rest)
    (if (null? rest)
        result
        (iter (op result (car rest))
              (cdr rest))))
  (iter initial sequence))
 
(define (reverse-right sequence)
  (fold-right (lambda (x y) (append y (list x))) '() sequence))
 
(define (reverse-left sequence)
  (fold-left (lambda (x y) (cons y x)) '() sequence))