1 665c255d 2023-08-04 jrmu (define x 10)
 2 665c255d 2023-08-04 jrmu (define s (make-serializer))
 3 665c255d 2023-08-04 jrmu (parallel-execute (s (lambda () (set! x (* x x))))
 4 665c255d 2023-08-04 jrmu 		  (s (lambda () (set! x (+ x 1)))))
 5 665c255d 2023-08-04 jrmu 
 6 665c255d 2023-08-04 jrmu (define (make-account balance)
 7 665c255d 2023-08-04 jrmu   (define (withdraw amount)
 8 665c255d 2023-08-04 jrmu     (if (>= balance amount)
 9 665c255d 2023-08-04 jrmu 	(begin (set! balance (- balance amount))
10 665c255d 2023-08-04 jrmu 	       balance)
11 665c255d 2023-08-04 jrmu 	"Insufficient funds"))
12 665c255d 2023-08-04 jrmu   (define (deposit amount)
13 665c255d 2023-08-04 jrmu     (set! balance (+ balance amount))
14 665c255d 2023-08-04 jrmu     balance)
15 665c255d 2023-08-04 jrmu   (let ((protected (make-serializer)))
16 665c255d 2023-08-04 jrmu     (define (dispatch m)
17 665c255d 2023-08-04 jrmu       (cond ((eq? m 'withdraw) (protected withdraw))
18 665c255d 2023-08-04 jrmu 	    ((eq? m 'deposit) (protected deposit))
19 665c255d 2023-08-04 jrmu 	    (else (error "Unknown request -- MAKE-ACCOUT" m))))
20 665c255d 2023-08-04 jrmu     dispatch))