suzanne.soy/racket
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Allow using `yield' with any number of arguments which will be returned

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as multiple values.  (These `case-lambda's are for making it fast, which
is probably stupid given how slow this is anyway.)

svn: r17981
This commit is contained in:
Eli Barzilay 2010-02-05 03:22:07 +00:00
parent f1dcf49d38
commit 2f62cb192e
1 changed files with 9 additions and 4 deletions
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13
collects/scheme/generator.ss
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@ -44,16 +44,21 @@
(lambda (v)
(error 'yield "must be called in the context of a generator"))))
(define (yield value)
((current-yielder) value))
(define yield
(case-lambda [() ((current-yielder))]
[(v) ((current-yielder) v)]
[vs (apply (current-yielder) vs)]))
(define yield-tag (make-continuation-prompt-tag))
(define-syntax-rule (generator body0 body ...)
(let ([state 'fresh])
(define (cont)
(define (yielder value)
(shift-at yield-tag k (set! cont k) value))
(define yielder
(case-lambda
[() (shift-at yield-tag k (set! cont k) (values))]
[(v) (shift-at yield-tag k (set! cont k) v)]
[vs (shift-at yield-tag k (set! cont k) (apply values vs))]))
(set! state 'running)
(reset-at yield-tag
(parameterize ([current-yielder yielder])