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Add `guard' form and test cases to R6RS (rnrs exceptions) library.

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* module/rnrs/6/exceptions.scm: (guard0, guard): New syntax.
* module/rnrs/records/6/procedural.scm: (r6rs-raise-continuable): Can't
  use `raise' here because it's exported by (rnrs exceptions); use plain
  old `throw' instead.
* test-suite/Makefile.am: Add tests/r6rs-exceptions.test to SCM_TESTS.
* test-suite/tests/r6rs-exceptions.test: New file.
This commit is contained in:
Julian Graham 2010-03-26 20:57:52 -04:00
parent a7ada16187
commit d1c83d388a
4 changed files with 122 additions and 2 deletions
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23
module/rnrs/6/exceptions.scm
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@ -18,10 +18,11 @@
(library (rnrs exceptions (6))
(export with-exception-handler raise raise-continuable)
(export guard with-exception-handler raise raise-continuable)
(import (rnrs base (6))
(rnrs conditions (6))
(rnrs records procedural (6))
(rnrs syntax-case (6))
(only (guile) with-throw-handler))
(define raise (@@ (rnrs records procedural) r6rs-raise))
@ -48,4 +49,24 @@
(continuation handler-return)
(raise (make-non-continuable-violation))))
*unspecified*))))
(define-syntax guard0
(lambda (stx)
(syntax-case stx ()
((_ (variable cond-clause ...) body)
(syntax (call/cc (lambda (continuation)
(with-exception-handler
(lambda (variable)
(continuation (cond cond-clause ...)))
(lambda () body)))))))))
(define-syntax guard
(lambda (stx)
(syntax-case stx (else)
((_ (variable cond-clause ... . ((else else-clause ...))) body)
(syntax (guard0 (variable cond-clause ... (else else-clause ...))
body)))
((_ (variable cond-clause ...) body)
(syntax (guard0 (variable cond-clause ... (else (raise variable)))
body))))))
)