Re: non-local exits are icky Michael Sperber (03 Jan 2004 16:16 UTC)
Re: non-local exits are icky Michael Sperber 03 Jan 2004 16:16 UTC
>>>>> "Tom" == Tom Lord <firstname.lastname@example.org> writes:
Tom> To test my understanding, and before replying to the proposal further,
Tom> let me just say back to you two things that I think you would agree
Tom> with (and think are obviously true):
Tom> 1) Non-local exits to upward continuations currently afford no
Tom> general mechanism for cleanups in FFI-using C.
Tom> Later SRFIs will have to add
Tom> additional mechanisms to the FFI to handle such situations.
Yes, provided that they are necessary. I'm not convinced they are,
but that's irrelevant here.
Tom> 2) The specification of error signalling could be made clearer:
That's probably true.
Tom> but is could say something more like:
Tom> The following macros explicitly signal certain errors.
Tom> If an error is signalled, either: [...]
That's arguable, but not what I intended. What I intended was that
the "an error is signalled" means the same thing as in R5RS, whatever
that is for a given Scheme implementation. In particular, what you
Tom> 1) the computation must be terminated
Tom> 2) the computation may be continued in part by invoking
Tom> a continuation which is upwards relative to the
Tom> C call that triggered the error. (see "Calling Scheme
Tom> procedures from C".)
... seems to leave as much room for interpretation as what's in there now.
Cheers =8-} Mike
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