[plt-scheme] R6RS exception handling and dynamic extent [was: SXML for R6RS]

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Thu Jul 10 11:08:42 EDT 2008

At Thu, 10 Jul 2008 10:00:42 -0500, "Robby Findler" wrote:
> I think I'm missing some earlier important part of this conversation
> and I wonder if it could be said again for others who might be like
> me?
> Why is guard causing problems (when combined with continuable
> exceptions, etc)?

Both `guard' and `with-handlers' jump out to the dynamic extent of the
`guard' or `with-handlers' form to check whether they want to handle a
given exception. At that point, if the right way to handle the
exception was to continue without jumps, then it's too late.

As specified by R6RS, `guard' will at least jump back in to try further
handlers --- but that facet of `guard' isn't in our implementation.


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