[r-t] Proposed definition of a peal
richard at ex-parrot.com
Thu Aug 7 02:17:19 UTC 2008
Matthew Frye wrote:
> Perhaps basing it on a lead wasn't the best idea, perhaps
> a plain course (which dixonoids have?)
The whole concept of a 'course' in dixonoids is fraught
First, the length of a course (without any calls) is
variable. In conventional Dixons, some courses are 64
changes long; others are 168 changes long. It would be
entirely possible to produce a dixonoid with one bell in the
same place for the whole of one type of course, but for all
the bells to be involved in a second type of course. This
is an issue in practice, because some otherwise-nice
dixonoids can include a type of course that is very
short -- perhaps only 4 changes long -- in which case, it
may very well have several bells fixed throughout.
Second, a course isn't necessarily a linear (well, circular)
sequence of rows. If you draw the main part of a course as
a loop with each row marked along the loop, some dixonoids
have additional 'tails' (which are potentially forked).
These are (generally short) sequences of rows that lead to
the loop, and once you're on the loop, you'll never get back
on to the tail. At the ends of the tails, you'll find a
handful of rows for which no predecesor exists under the
rules of dixonoid.
These things make composing true extents harder, but that's
not relevant here. What is relevant is that using the word
'course' opens up a whole minefield of problems if a
dixonoid is involved.
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