Newsgroups: rec.arts.int-fiction
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From: goetz@cs.buffalo.edu (Phil Goetz)
Subject: Re: Undo
Message-ID: <CMB72A.2t3@acsu.buffalo.edu>
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Organization: State University of New York at Buffalo/Comp Sci
Date: Mon, 7 Mar 1994 19:20:32 GMT
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In a logic-based IF, you might tag all assertions in the database with
a time, and keep an extralogical pointer to NOW.  All you need to do to
UNDO is to step back the pointer and retract all the information tagged
with the erased moment.

How do you implement UNDO in a different system?  TADS can undo a long
way back.  How does it keep track of the past?

Phil
