(define (make-account balance password)
(define (withdraw amount)
(if (>= balance amount)
(begin (set! balance (- balance amount))
balance)
"Insufficient funds"))
(define (deposit amount)
(set! balance (+ balance amount))
balance)
(define (dispatch pw m)
(begin (unless (eq? pw password) (error "Incorrect password"))
(cond ((eq? m 'withdraw) withdraw)
((eq? m 'deposit) deposit)
(else (error "Unknown request -- MAKE-ACCOUNT" m)))))
dispatch)
(define (make-joint account pass new-pass)
(define (joint pw m)
(begin (unless (eq? pw new-pass) (error "Incorrect password"))
(account pass m)))
(account pass 'deposit)
joint)
(define peter-acc (make-account 1000 'open-sesame))
(define paul-acc (make-joint peter-acc 'open-sesame 'rosebut))