eharetea

Utilizing environments to make classes and objects.

Utilizing environments to make classes and objects.

Date Created:Tuesday October 14th, 2008 10:07 AM
Date Modified:Tuesday October 14th, 2008 10:40 AM

(define (make-account init-amount)
  (let (
        (balance init-amount)
        (init init-amount)
        (transactions '())
       )
    (define (withdraw amount)
      (begin
      (set! balance (- balance amount)) 
      (set! transactions (cons (cons (- amount) balance) transactions))
      balance))
    (define (deposit amount)
      (begin
      (set! balance (+ balance amount))
      (set! transactions (cons (cons amount balance) transactions))
      balance))
    (define (dispatch msg)
      (cond
        ((eq? msg 'balance) balance)
        ((eq? msg 'init-amount) init)
        ((eq? msg 'transactions) transactions)
        ((eq? msg 'withdraw) withdraw)
        ((eq? msg 'deposit) deposit)))
     dispatch))

Environments by Dan Lynch
is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License
Based on a work at www.3daet.com
Permissions beyond the scope of this license may be available at http://www.3daet.com