Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!gateway!RELAY.NSWC.NAVY.MIL!dsill
From: dsill@RELAY.NSWC.NAVY.MIL
Newsgroups: comp.emacs
Subject: Turing-equivalent Editors (was Re: Copy from Above?)
Message-ID: <36098@bbn.COM>
Date: 16 Feb 89 17:24:51 GMT
Sender: news@bbn.COM
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unsigned *Wayne_Mesard(); MESARD@BBN.COM writes:
>[[Hypothesis of the day: It is possible to build an arbitrarily complex
>Turing machine using Emacs keyboard macros :-) ]]
>
>[[Followups refuting the previous sentence ... to /dev/null.]]

How about a weak proof?

A year ago today, coincidentally, David Hitz (hitz@mips.com) posted a
set of vi macros that simulate Turing machines to comp.unix.wizards.
If one of the vi emulators for GNU emacs handles vi macros, then it
would be possible to simulate a Universal Turing Machine under vi
under emacs.

Of course it would be easy to write a Turing machine simulator in
elisp, but that'd be cheating.

(We are assuming in this discussion that a simulated Turing machine is
equivalent to a real Turing machine, which is not true.  That's like
saying simulated perpetual-motion machines really demonstrate
perpetual motion.)

:-)

================================================================
"No, I'm not interested in developing a powerful brain.  All I'm after
is just a mediocre brain, something like the president of American
Telephone and Telegraph Company."
					-- Alan Turing