Re: why args are invalid syntaxes in syntax-rules

["Marco Maggi" <marco.maggi-ipsu@poste.it>]

"Stephen Compall" wrote:
>On Sat, 2007-10-13 at 08:37 +0200, Marco Maggi wrote:
>> (body ?args ?body)
>
>First, invoke that instead of this.  Second, does the above
pattern
>match the below syntax?
>
>>       (body ()
>>       (display 'ciao)
>>       (newline))

Thanks and  sorry, I did  multiple errors in  converting the
real code into an example. The correct example syntax is:

|(define-syntax that
|  (syntax-rules (body handler)
|    ((_ (body ?body ...)
|        (handler ?handler-args ?handler ...))
|     (catch #t
|       (lambda ()
|         ?body ...)
|       (lambda ?handler-args
|         ?handler ...)))))
|
|(that (body
|        (display 'ciao)
|        (newline))
|      (handler (key . args)
|        #f))

and for the curious the real code is (now fixed, I hope):

|(define-syntax with-deferred-exceptions
|  (syntax-rules (exception-handler
deferred-exception-handler lambda begin)
|
|    ((_ (lambda () ?body ...)
|        (lambda ?handler-args ?handler ...)
|        (lambda ?deferred-args ?deferred-handler ...))
|     (with-fluids ((*gee-deferred-exceptions* '()))
|       (gee-K (catch #t
|                (lambda () ?body ...)
|                (lambda ?handler-args (deferred-catch
?handler ...)))
|              (run-deferred-exceptions-handler
|               (lambda ?deferred-args ?deferred-handler
...)))))
|
|    ((_ (begin ?body ...)
|        (exception-handler ?handler-args ?handler ...)
|        (deferred-exception-handler ?deferred-args
?deferred-handler ...))
|     (with-deferred-exceptions
|       (lambda () ?body ...)
|       (lambda ?handler-args ?handler ...)
|       (lambda ?deferred-args ?deferred-handler ...)))
|
|    ((_ (begin ?body ...) ?first ?form ...)
|     (with-deferred-exceptions (begin ?body ... ?first)
?form ...))
|
|    ((_ ?first ?form ...)
|     (with-deferred-exceptions (begin ?first) ?form ...))))

which accepts both the forms:

|(with-deferred-exceptions
|    (this)
|    (that)
|  (exception-handler (key . args)
|    (do-some-thing))
|  (deferred-exception-handler (key . args)
|    (do-some-other-thing)))
|
|(with-deferred-exceptions
|  (lambda ()
|    (this)
|    (that))
|  (lambda (key . args)
|    (do-some-thing))
|  (lambda (key . args)
|    (do-some-other-thing)))

converting the first into the second, and eventually into:

|(with-fluids ((*gee-deferred-exceptions* '()))
|   (gee-K (catch #t
|            (lambda () (this) (that))
|            (lambda (key . args) (deferred-catch
(do-some-thing))))
|          (run-deferred-exceptions-handler
|           (lambda (key . args) (do-some-other-thing)))))

--
Marco Maggi

"Now feel the funk blast!"
Rage Against the Machine - "Calm like a bomb"




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