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fix+reinstall last force version

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svn: r6934
This commit is contained in:
Eli Barzilay 2007-07-19 02:48:42 +00:00
parent b5861250f7
commit f4a7b72482
1 changed files with 3 additions and 30 deletions
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33
collects/lazy/promise.ss
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@ -143,15 +143,14 @@
;; actually it doesn't work with `lazy' holding `lazy' of multiple values, so
;; `lazy' works with multiple values unless rewrapped in `lazy'.)
;; #;
#;(define (force promise)
(define (force promise)
(if (promise? promise)
(let loop ([p (p:ref promise)])
(cond
[(procedure? p)
(p:set! promise #f) ; mark root for cycle detection
(let ([vals* (call-with-values p list)])
(if (and (pair? vals*)
(null? (cdr vals*)))
(if (and (pair? vals*) (null? (cdr vals*)))
(let loop1 ([val* (car vals*)])
(if (promise? val*)
(let loop2 ([promise* val*])
@ -166,7 +165,7 @@
[else (error 'force
"invalid promise, contains ~e" p*)])))
(begin ; error here for "library approach" (see above URL)
(p:set! promise vals*)
(p:set! promise (list val*))
val*)))
(begin ; error here for "library approach" (see above URL)
(p:set! promise vals*)
@ -178,32 +177,6 @@
;; different from srfi-45: identity for non-promises
promise))
(define (force promise)
(if (promise? promise)
(let loop ([p (p:ref promise)])
(cond
[(procedure? p)
(p:set! promise #f) ; mark root for cycle detection
(let loop ([promise* (p)])
(if (promise? promise*)
(let ([p* (p:ref promise*)])
(p:set! promise* promise) ; share with root
(cond [(procedure? p*) (loop (p*))]
[(pair? p*) (p:set! promise p*) (car p*)]
[(promise? p*) (loop p*)]
[(not p*) (error 'force "reentrant promise")]
[else (error 'force
"invalid promise, contains ~e" p*)]))
(begin ; error here for "library approach" (see above URL)
(p:set! promise (list promise*))
promise*)))]
[(pair? p) (car p)]
[(promise? p) (loop (p:ref p))]
[(not p) (error 'force "reentrant promise")]
[else (error 'force "invalid promise, contains ~e" p)]))
;; different from srfi-45: identity for non-promises
promise))
#|
Timing results (#1, #2, #3 are the above versions), in Lazy Scheme: