练习3-45
原文
Exercise 3.45. Louis Reasoner thinks our bank-account system is unnecessarily complex and error-prone now that deposits and withdrawals aren’t automatically serialized. He suggests that make-accountand-serializer should have exported the serializer (for use by such procedures as serializedexchange) in addition to (rather than instead of) using it to serialize accounts and deposits as makeaccount did. He proposes to redefine accounts as follows:
(define (make-account-and-serializer balance) (define (withdraw amount) (if (>= balance amount) (begin (set! balance (- balance amount)) balance) "Insufficient funds")) (define (deposit amount) (set! balance (+ balance amount)) balance) (let ((balance-serializer (make-serializer))) (define (dispatch m) (cond ((eq? m 'withdraw) (balance-serializer withdraw)) ((eq? m 'deposit) (balance-serializer deposit)) ((eq? m 'balance) balance) ((eq? m 'serializer) balance-serializer) (else (error "Unknown request -- MAKE-ACCOUNT" m)))) dispatch))
Then deposits are handled as with the original make-account:
(define (deposit account amount) ((account 'deposit) amount))
Explain what is wrong with Louis’s reasoning. In particular, consider what happens when serializedexchange is called.
代码
临时发现有误,待完成。
感谢访问,希望对您有所帮助。 欢迎关注或收藏、评论或点赞。
为使本文得到斧正和提问,转载请注明出处:
http://blog.youkuaiyun.com/nomasp
版权声明:本文为 NoMasp柯于旺 原创文章,未经许可严禁转载!欢迎访问我的博客:http://blog.youkuaiyun.com/nomasp
Louis认为当前的银行账户系统过于复杂且易出错,提议重新定义账户,使其更简洁。他的方案中,make-account和serializer不仅用于序列化账户和存款,还导出了serializer供其他过程使用。然而,这一改动在实际应用中可能引发问题,尤其是在处理serialized exchange调用时。
949

被折叠的 条评论
为什么被折叠?



