Xref: utzoo rec.puzzles:8231 sci.math:15538 comp.theory.cell-automata:309 Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!noao!ncar!ames!vsi1!zorch!xanthian From: xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) Newsgroups: rec.puzzles,sci.math,comp.theory.cell-automata Subject: Re: How Intelligent are the Winning Ways? Message-ID: <1991Mar5.171804.1429@zorch.SF-Bay.ORG> Date: 5 Mar 91 17:18:04 GMT References: <5539@acorn.co.uk> Distribution: rec Organization: SF-Bay Public-Access Unix Lines: 20 In article <5539@acorn.co.uk> dseal@armltd.uucp (David Seal) writes: > Incidentally, how would one go about building a Life Turing machine? I > can see one very long-winded technique, with a stationary tape and a > moving state machine: the state machine could move by emitting fleets > of gliders to (a) destroy itself; (b) reassemble an exact copy of > itself one tape spacing to the left or right. However, this seems like > an awful lot of work: a moving tape, stationary state machine Turing > machine would seem a lot more efficient. Any ideas how the moving tape > might be constructed? Won't work, or at least won't act like a Turing machine. You have to be able to reverse direction on the tape. Rebuilding the head one space left rather than one space right is at least feasible, but reversing the motion of a tape which is by definition infinite in length is not. Kent, the man from xanth.