Article View: comp.theory
Article #1891Re: Real Numbers vs. Rational Numbers?
From: Andrew Butterfield
Date: Wed, 06 Jan 1993 16:11
Date: Wed, 06 Jan 1993 16:11
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1954 bytes
In article <1993Jan5.161955.11237@tom.rz.uni-passau.de>, boerncke@kirk.fmi.uni-passau.de (Frank-Roland Boernke) wrote: > > So what does this mean in the end? When I introduced this subject, I asked, > whether a Turing Machine, that handles not only bits or naturals but also > real numbers is more powerful, than a turing machine, that only works > with natural numbers. > > My professor said, both types of Turing Machines are the same concerning > their power of computability. I claimed that can't be true, refering to > ideas like the ones mentioned in the quotes at the beginning of this side. > When you say "handles real numbers", do you mean that it can write real numbers into a single box on the tape ? If this is the case then your "R-Turing" machine is different to a classic one, which has a potentially infinite tape, but only a finite set of symbols that it can write on the tape. The R-Turing machine has an uncountably infinite set of symbols. It would also need an uncountably infinite transition function to exploit the power of its symbol set. A classic Turing machine can "handle" real numbers in the same way as any other computing devices, by working with finite approximations of those real numbers.
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Newsgroups: comp.theory Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!ieunet!tcdcs!butrfeld.cs.tcd.ie!user From: butrfeld@cs.tcd.ie (Andrew Butterfield) Subject: Re: Real Numbers vs. Rational Numbers? Message-ID: <butrfeld-060193160334@butrfeld.cs.tcd.ie> Followup-To: comp.theory Sender: usenet@cs.tcd.ie (NN required at ashe.cs.tcd.ie) Nntp-Posting-Host: butrfeld Organization: Dept. of Comp. Sci., TCD References: <1992Dec17.142150.7932@tom.rz.uni-passau.de> <1hi8dvINN5l2@uwm.edu> <1993Jan3.151347.29159@tom.rz.uni-passau.de> <4287@dozo.and.nl> <butrfeld-050193140552@butrfeld.cs.tcd.ie> <1993Jan5.161955.11237@tom.rz.uni-passau.de> Distribution: inet Date: Wed, 6 Jan 1993 16:11:53 GMT Lines: 26