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; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Richard Kelsey, Jonathan Rees
; For an explanation, see comments in rts/low.scm.
; The debugger invokes EXTRACT-CONTINUATION on a "native" continuation
; as obtained by PRIMITIVE-CWCC in order to get a VM continuation.
; The distinction between native and VM continuations is useful when
; debugging a program running under a VM that's different from
; whatever machine is running the debugger.
(define-record-type escape :escape
(make-escape proc)
(proc escape-procedure))
(define (with-continuation esc thunk)
(if esc
((escape-procedure esc) thunk)
(let ((answer (thunk)))
(signal 'vm-return answer) ;#f means halt
(assertion-violation 'with-continuation "halt" answer))))
(define (primitive-cwcc proc)
(call-with-current-continuation
(lambda (done)
((call-with-current-continuation
(lambda (k)
(call-with-values
(lambda ()
(proc (make-escape k)))
done)))))))
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