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;; This replaces trans-id REF in Reppy's code
(define-synchronized-record-type trans-id :trans-id
(really-make-trans-id thread-cell value)
(value)
trans-id?
(thread-cell trans-id-thread-cell)
(value trans-id-value set-trans-id-value!))
(define (make-trans-id)
(really-make-trans-id (make-cell (current-thread))
#f))
(define (maybe-commit-and-trans-id-value trans-id)
(cond
((trans-id-value trans-id)
=> (lambda (value)
(and (maybe-commit)
value)))
(else
(and (maybe-commit-and-block (trans-id-thread-cell trans-id))
(trans-id-value trans-id)))))
(define (trans-id-set-value! trans-id value)
(cond
((not value) (error "trans-id value can't be #f" trans-id value))
((trans-id-value trans-id)
(error "trans-id is already assigned"))
(else
(set-trans-id-value! trans-id value))))
(define (trans-id-cancelled? trans-id)
(and (trans-id-value trans-id) #t))
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