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Re: Procedure proposal: call-with-escape-procedure


From: Martin Grabmueller
Subject: Re: Procedure proposal: call-with-escape-procedure
Date: Tue, 06 Mar 2001 08:25:31 +0100

[Wow, and I only wanted one little procedure...]

> From: Marius Vollmer <address@hidden>
> Date: 06 Mar 2001 02:34:37 +0100
> 
> We will also need a condition system of some sort.  With this, I mean
> the establishment of catch points that will catch certain kinds of
> exceptional situations.  Raising such an exception corresponds to
> finding the right escape procedure and invoking it.

On the long term, I would really like to see that exceptions are
somehow implemented as GOOPS classes, because we could then specify
which exceptions to catch as one can in Java.  I think the current
system (catch all or only one) is not fine-grained enough.  Just think
about how many different error situations are signalled as a
`misc-error'.

> The important thing here is that continuations created by call/cc do
> not run the escape handlers established by escape-protect.

Why not? Because `escape-protect' is just for cleanup?

> Here is a possible, naive implementation, going from call/cc and
> dynamic-wind to catch and throw.  This is not in any way meant to
> replace the stuff we already have, only to help me make my thoughts
> more concrete and to have a basis for discussing the fine points.
> When we agree upon some semantics that are different from what we have
> now, we can modify Guile to implement them efficiently.

I don't claim to understand all possible semantic implications, but as
call/ec is included in the suggestion, I am happy with that.  But of
course I am interested in the `implement them efficiently' part,
because that got the whole thing started ;-)

Regards,
  'martin



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