;; revers : list-of-string -> list-of-string
;; produce list of string with strings in opposite order from given list
(define (revers alos)
  (rev-accum alos empty))


;; rev-accum : list-of-string list-of-string -> list-of-string
;; accumulates reverse of first list in second list
(define (rev-accum alos revalos)
  (cond [(empty? alos) revalos]
        [(cons? alos) (rev-accum (rest alos) (cons (first alos) revalos))]))



;; reverse2 : list-of-string -> list-of-string
;; produce list of string with strings in opposite order from given list
(define (reverse2 alos)
  (cond [(empty? alos) empty]
        [(cons? alos) (append (reverse (rest alos))
                              (list (first alos)))]))



------------------------------------------------------------------


;; an account is a struct
;; (make-account number number)
(define-struct account (acctnum balance))

;; a list-of-account is either
;; empty, or 
;; (cons account list-of-account)

;; Citibank:  list-of-account
;; state variable that remembers the current contents of each bank account
(define Citibank (list (make-account 1 500)
                       (make-account 2 1000)
                       (make-account 3 10)))


;; add-account:  number number  -> void
;; consumes an acount number and amount, and adds a new account
;; EFFECT:  changes the number of accounts in Citibank
(define (add-account acctnum amt)
  (set! Citibank (cons (make-account acctnum amt) Citibank)))