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From: Tom I Helbekkmo <tih@hamartun.priv.no>
Subject: Re: Common LISP: The Next Generation
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Date: Wed, 4 Sep 1996 15:59:20 GMT
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[Mike Haertel]

> I think what I'd really like would be some sort of checkpoint and
> rollback feature.  So, if some definition doesn't work, there should
> be a way to undo it as if it had never happened, up to and including
> restoring the previous definition if any.

[Erik Naggum]

> yes!  I'd love that.  but this would require that all symbols had a
> history of the previous contents of their various slots that worked
> independently of scoping.

How about something along the lines of the SmallTalk "changes" file
concept?  It keeps a log of all changes made, in clear text, and in
such a format that it can be read into a running SmallTalk system.
If you screw up badly, you go back to the previous snapshot of the
image, edit the "changes" file to remove or fix what you did wrong,
before you roll it back in.

Something like this might be feasible for Lisp -- but not easy.

-tih
-- 
Tom Ivar Helbekkmo
tih@Hamartun.Priv.NO
