27 lines
844 B
Scheme
27 lines
844 B
Scheme
;; SRFI 34 for PLT Scheme
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;; Zhu Chongkai, April 2005
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;; <mrmathematica@yahoo.com>
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(module exception mzscheme
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(provide with-exception-handler
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guard
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raise)
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(define-syntax with-exception-handler
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(syntax-rules ()
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((_ handler thunk)
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(with-handlers (((lambda (exn) #t) handler)) (thunk)))))
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(define-syntax guard
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(syntax-rules (else)
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((_ (var clause ... (else de ...)) e1 e2 ...)
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(with-handlers (((lambda (exn) #t)
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(lambda (var) (cond clause ...
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(else de ...)))))
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e1 e2 ...))
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((_ (var clause ...) e1 e2 ...)
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(with-handlers (((lambda (exn) #t)
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(lambda (var) (cond clause ...
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(else (raise var))))))
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e1 e2 ...)))))
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