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minor reorganizations

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svn: r16743
This commit is contained in:
Eli Barzilay 2009-11-13 12:27:42 +00:00
parent 2153c258db
commit 82f10f35a5
1 changed files with 4 additions and 5 deletions
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9
collects/scheme/promise.ss
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@ -44,9 +44,6 @@
(for-each (lambda (x) (fprintf port fmt x)) p)) (for-each (lambda (x) (fprintf port fmt x)) p))
(display ")>" port)]))) (display ")>" port)])))
(define-struct promise (val)
#:mutable
#:property prop:custom-write promise-printer)
;; A promise value can hold ;; A promise value can hold
;; - (list <value> ...): forced promise (possibly multiple-values, usually one) ;; - (list <value> ...): forced promise (possibly multiple-values, usually one)
;; - <promise>: a shared (redirected) promise that points at another one ;; - <promise>: a shared (redirected) promise that points at another one
@ -54,6 +51,8 @@
;; - can also hold a `running' thunk that will throw a reentrant error ;; - can also hold a `running' thunk that will throw a reentrant error
;; - can also hold a raising-a-value thunk on exceptions and other ;; - can also hold a raising-a-value thunk on exceptions and other
;; `raise'd values (actually, applicable structs for printouts) ;; `raise'd values (actually, applicable structs for printouts)
(define-struct promise ([val #:mutable])
#:property prop:custom-write promise-printer)
;; Creates a `composable' promise ;; Creates a `composable' promise
;; X = (force (lazy X)) = (force (lazy (lazy X))) = (force (lazy^n X)) ;; X = (force (lazy X)) = (force (lazy (lazy X))) = (force (lazy^n X))
@ -121,8 +120,8 @@
(cond [(procedure? p) (cond [(procedure? p)
;; mark the root as running: avoids cycles, and no need to keep ;; mark the root as running: avoids cycles, and no need to keep
;; banging the root promise value; it makes this non-r5rs, but ;; banging the root promise value; it makes this non-r5rs, but
;; only practical uses of these things could be ones that use ;; the only practical uses of these things could be ones that use
;; state. ;; state to avoid an infinite loop.
;; (careful: avoid holding a reference to the thunk, to allow ;; (careful: avoid holding a reference to the thunk, to allow
;; safe-for-space loops) ;; safe-for-space loops)
(set-promise-val! promise (make-running (object-name p))) (set-promise-val! promise (make-running (object-name p)))