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better code organization

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svn: r8116
This commit is contained in:
Eli Barzilay 2007-12-24 12:24:46 +00:00
parent f6abcd7fbf
commit e3f8d7e74b
1 changed files with 27 additions and 34 deletions
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61
collects/scheme/promise.ss
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@ -86,8 +86,28 @@
(define handle-results
(case-lambda
[(single) (values #t single)]
[multi (values #f multi)]))
[(single) (values #f single)]
[multi (values #t multi)]))
(define (force-proc p root)
(define (return-vals vals)
;; error here for "library approach" (see above URL)
(set-promise-val! root vals)
(apply values vals))
(let loop1 ([p p])
(let-values ([(multi? v) (call-with-values p handle-results)])
(if multi?
(return-vals v)
(if (promise? v)
(let loop2 ([promise* v])
(let ([p* (promise-val promise*)])
(set-promise-val! promise* root) ; share with root
(cond [(procedure? p*) (loop1 p*)]
[(or (pair? p*) (null? p*)) (return-vals p*)]
[(promise? p*) (loop2 p*)]
[else p*])))
(return-vals
(if (or (null? v) (pair? v) (procedure? v)) (list v) v)))))))
(define (force promise)
(if (promise? promise)
@ -96,38 +116,11 @@
[(procedure? p)
;; mark root for cycle detection:
(set-promise-val! promise running)
(with-handlers* ([void (lambda (e)
(set-promise-val! promise
(lambda () (raise e)))
(raise e))])
(let-values ([(single? vals*) (call-with-values p handle-results)])
(if single?
(let loop1 ([val* vals*])
(if (promise? val*)
(let loop2 ([promise* val*])
(let ([p* (promise-val promise*)])
(set-promise-val! promise* promise) ; share with root
(cond [(procedure? p*)
(let-values ([(single? vals)
(call-with-values
p* handle-results)])
(if single?
(loop1 vals)
(begin (set-promise-val! promise vals)
(apply values vals))))]
[(or (pair? p*) (null? p*))
(set-promise-val! promise p*)
(apply values p*)]
[(promise? p*) (loop2 p*)]
[else p*])))
(begin ; error here for "library approach" (see above URL)
(if (or (null? val*) (pair? val*) (procedure? val*))
(set-promise-val! promise (list val*))
(set-promise-val! promise val*))
val*)))
(begin ; error here for "library approach" (see above URL)
(set-promise-val! promise vals*)
(apply values vals*)))))]
(with-handlers*
([void (lambda (e)
(set-promise-val! promise (lambda () (raise e)))
(raise e))])
(force-proc p promise))]
[(or (pair? p) (null? p)) (apply values p)]
[(promise? p) (loop (promise-val p))]
[else p]))