sicp exercise 2.18

; Exercise 2.18. Define a procedure reverse that takes a list as argument and returns
; a list of the same elements in reverse order:
; (reverse (list 1 4 9 16 25))
; (25 16 9 4 1)


(define NULL (list))

(define (reverse mylist)
  (define reverse_impl (lambda (items result)
    (if (null? items) result
        (reverse_impl (cdr items) (cons (car items) result)))))
        (reverse_impl mylist NULL))

(display (reverse (list 1 2 3 4 5)))(newline)
(display (reverse (list 1 2 3 4 5 (list 10 9 8))))(newline)