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Re: [Scheme-reports] 6.11 Exceptions
On Wed 09 Jan 2013 03:07, Alex Shinn <alexshinn@x> writes:
> Secondly, its presence prohibits useful behaviors. For example, it
> would be easy to make a `call-with-port' that closes its port on
> exceptional exits by installing a throw handler. However, since
> handlers are also used for raise-continuable, this is not possible.
> Releasing resources can be done manually at the programmer
> level with their own exception handlers, even wrapping common
> patterns such as `call-with-port/close-on-exception'.
My point is precisely that you cannot implement this behavior when
raise-continuable follows the same dispatch as raise. Imagine:
(lambda (ex) #t)
What definition of call-with-port/do-the-right-thing will actually leave
the port open after the raise-continuable?
> Guardians also allow for easy and arbitrary finalization.
Please. Relying on GC to run (and thus adding ports to guardians) is
not a solution in cases of limited resources like file descriptors.
> Ports in particular should be closed automatically on GC, and
> out-of-file-descriptor errors should trigger GC.
Yes, but the overhead of this is significantly higher in terms of pause
times. I've always found that "call (gc)" is the wrong answer.
Anyway I don't think we will agree here. I think the R7RS is making the
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