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minor fixes

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svn: r16012
This commit is contained in:
Eli Barzilay 2009-09-14 21:21:28 +00:00
parent 9f10bc960b
commit 80a386e482
1 changed files with 25 additions and 24 deletions
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49
collects/scheme/generator.ss
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@ -8,7 +8,8 @@
;; (define-syntax-parameter yield
;; (lambda (stx)
;; (raise-syntax-error #f "yield is only bound inside a sequence generator")))
;; (raise-syntax-error
;; #f "yield is only bound inside a sequence generator")))
;; (define (procedure->generator proc)
;; (define tag (make-continuation-prompt-tag))
@ -20,10 +21,27 @@
;; r)))
;; (lambda () (cont)))
;; not using parameterization
#;
(define-syntax-rule (generator body0 body ...)
(let ([tag (make-continuation-prompt-tag)])
(define yielder
(let ([yield (lambda (value) (shift-at tag k (set! cont k) value))])
yield))
(splicing-syntax-parameterize ([yield (make-rename-transformer #'yielder)])
(define (cont)
(reset-at tag
(let ([retval (begin body0 body ...)])
;; normal return:
(set! cont (lambda () retval))
retval))))
(define (generator) (cont))
generator))
(define current-yielder
(make-parameter
(lambda (v)
(error 'yield "yield cannot be called when no generator is active"))))
(error 'yield "must be called in the context of a generator"))))
(define (yield value)
((current-yielder) value))
@ -36,28 +54,11 @@
(define (yielder value)
(shift-at yield-tag k (set! cont k) value))
(reset-at yield-tag
(parameterize ([current-yielder yielder])
(let ([retval (begin body0 body ...)])
;; normal return:
(set! cont (lambda () retval))
retval))))
(define (generator) (cont))
generator))
;; not using parameterization
#;
(define-syntax-rule (generator body0 body ...)
(let ([tag (make-continuation-prompt-tag)])
(define yielder
(let ([yield (lambda (value) (shift-at tag k (set! cont k) value))])
yield))
(splicing-syntax-parameterize ([yield (make-rename-transformer #'yielder)])
(define (cont)
(reset-at tag
(let ([retval (begin body0 body ...)])
;; normal return:
(set! cont (lambda () retval))
retval))))
(parameterize ([current-yielder yielder])
(let ([retval (begin body0 body ...)])
;; normal return:
(set! cont (lambda () retval))
retval))))
(define (generator) (cont))
generator))