[next] [prev] [up] Date: Mon, 08 Dec 80 13:09:00 -0500 (EST)
[next] ~~~ [up] From: Guy Steele <Guy.Steele@CMU-10A >
[next] [prev] [up] Subject: Re: That 28 move Plummer Cross

A QTW cannot take you between two positions of equal distance, I believe
-- is there not some parity quantity obeyed by QTW's (net twist of
the six center cubies)? If so, then there cannot be two positions of
equal distance separated by a QTW, for then there would be an odd
length identity transformation, which would violate parity.
(In the example you gave, there are *not* two positions of
equal distance, but only one -- the halfway point.)

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