[r-t] What IS a rotation of a method?

Graham John graham at changeringing.co.uk
Thu Oct 16 22:45:17 UTC 2014

Don wrote:

> I don't think I've ever actually seen an explicit definition
> of what we mean by "rotation" of a method.

The CC XML specification contains the following definition(s).

Round Block:
A round block is an ordered sequence of rows (each at the same stage)
produced by a sequence of two or more changes where the final change in the
sequence produces the initial row of the block. A round block B is said to
be a rotation of a round block A if the sequence of changes that produces B
is a rotation of the sequence of changes that produces A.

Any round block that is true (i.e. contains no row more than once) and is
divisible into two or more equal parts (called leads), and has more working
bells than hunt bells, defines a method. Such a round block is called the
plain course of the method. Starting the plain course from a different
change does not give a different method, so two round blocks that are
rotations of one another both define the same method.


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