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| #lang sicp
(#%require (only racket/base error))
(define (make-account balance secretpwd)
(let ((times 0))
(define (withdraw amount)
(if (>= balance amount)
(begin (set! balance (- balance amount))
balance)
"Insufficient funds"))
(define (deposit amount)
(set! balance (+ balance amount))
balance)
(define (dispatch pwd m)
(if (eq? secretpwd pwd)
(begin (set! times 0)
(cond ((eq? m 'withdraw) withdraw)
((eq? m 'deposit) deposit)
(else (error "Unknown request -- MAKE-ACCOUNT"
m))))
(if (> times 6)
(begin (call-the-cops) (error "Some error happend. Please wait..."))
(begin (set! times (+ times 1))
(error "Invalid Password")))))
dispatch))
(define (call-the-cops)
(error "Cops coming!"))
|