[r-t] Complexity of extents
pabs at cantab.net
Fri Jun 28 18:59:10 UTC 2013
See RW 1999 p728. The extent consisted of two 10-part blocks (part end
5123476), with the rows of one being inverted and rung backwards to give
On 28/06/2013 14:24, Alexander Holroyd wrote:
> I vaguely remember that PABS had an extent of the principle
> 220.127.116.11.7.1.345 with calls 3 and 5 that exploited an unusual kind of
> symmetry. (Perhaps he would care to remind us).
> On Mon, 24 Jun 2013, Richard Smith wrote:
>> Andrew Johnson wrote:
>>>> From: Richard Smith <richard at ex-parrot.com>
>>>> But when I try to get an extent with rotational symmetry, it
>>>> feels like I'm fighting against the symmetry rather than
>>>> utilising it.
>>> It's not an extent, but for rotational symmetry were
>>> you thinking of compositions such as Ander's 5024 Bristol S.
>> Not really. I think the difference between an extent an
>> eighth-extent (a peal of major) is significant. I was thinking more
>> of extents on four, five or six. I can't say I've ever tried to
>> produce a rotationally symmetric peal of major.
>> Naïvely you wouldn't necessarily expect a rotationally symmetric
>> extent to be any harder to produce than a palindromic one. Both
>> symmetries constrain half of the rows. But, at least in my
>> experience, a rotationally symmetric extent (that's not also
>> palindromic) feels a much tougher proposition than a palindromic one.
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