[next] [prev] [up] Date: Thu, 08 Jan 81 20:06:00 -0600 (CST)
[next] ~~~ [up] From: Bill Vaughan <VaughanW.REFLECS@HI-Multics >
[next] ~~~ [up] Subject: Befuddled by BFUDLR

This is a plea for another notation.

BFUDLR is sufficient to describe anything. So what? It's about as
readable as a LISP s-expression, as rich as the average grad
student, and (my particular gripe) it's impossible to express an
elegant sequence in it and keep any of the elegance.

I want to keep this short, so I'll only give a few examples. The
first is the Sprat Wrench. BFUDLR calls it: RL'URL'BRL'DRL'F. But
the way most everyone does it, it's: (XU)*4, where X means "move
the LR slice clockwise as viewed from the left."

The next example (I don't know its name) flips all top and bottom
edges. BFUDLR calls it: LRUDFBLRUDFB. Interesting, but this is
nicer: (R-B-)*3, where "foo-" means "foo antislice" and is done by
twisting foo and its adjacent slice clockwise 1qtw, then twisting
foo another qtw.

A move yielding (RF, BL, RB) has been published (Don Woods 6 Jan
81) in BFUDLR as: BRL'D'RRDR'LB'RR. Now where's the symmetry in
that? But annotate the same move BXB'RR.BX'B'RR (X as in first
example) and you can see how pretty it is. And it's a lot easier
to remember.

The key is that the fixed orientation of the center cubies
shouldn't be a sacred cow. Often, keeping a corner cubie as a
fixed point will yield a far more natural notation.

The commonest compound moves: slice, antislice, and possibly
Singmaster's Y and Z commutators, should have specialized
notations. A move that I use commonly in solving the cube is a
monotwist: Y(f,r)*2.L.Y'(f,r)*2.L'. That's a lot harder to
understand as: FR'F'RFR'F'RLR'FRF'R'FRF'L'.

I don't have good notations to offer for slice and antislice. What
I do with paper and pencil involves overstrikes that my CRT can't
handle. Something nice and linear is needed, with all the
characters in ASCII. Any suggestions, anyone?

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