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Adding exception-protect.

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Alex Shinn 2014-03-21 10:20:00 +09:00
parent ad83b1b00c
commit 0001f0bdcb
1 changed files with 23 additions and 0 deletions
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23
lib/init-7.scm
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@ -994,6 +994,29 @@
(begin result1 result2 ...)
(protect-aux reraise clause1 clause2 ...)))))
;; Similar to unwind-protect, but allows escape via continuations
;; assuming they'll return, whereas exceptions are assumed to not return.
(define (with-exception-protect thunk final)
(let ((finalized? #f)
(run-finalize
(lambda ()
(cond ((not finalized?)
(set! finalized? #t)
(final))))))
(with-exception-handler
(lambda (exn)
(run-finalize)
(raise exn))
(lambda ()
(let ((res (thunk)))
(run-finalize)
res)))))
(define-syntax exception-protect
(syntax-rules ()
((exception-protect expr final)
(with-exception-protect (lambda () expr) (lambda () final)))))
(define (eval x . o)
(let ((thunk (compile x (if (pair? o) (car o) (interaction-environment)))))
(if (procedure? thunk) (thunk) (raise thunk))))