# [r-t] Doubles 240s

Don Morrison dfm at ringing.org
Thu Mar 19 14:31:17 UTC 2015

```On Thu, Mar 19, 2015 at 10:14 AM, Alan Reading <alan.reading at googlemail.com>
wrote:
> It strikes me John is using definition 1, whereas Ander is using
> definition 2. I had assumed definition 2, just the difference
> between a legal and a mathematical background I guess.

So the problem is just a poor choice of name. The solution is obvious:
change the name. Let's just call it the "identity change", and no one
will be unhappy.

Even better, don't give it a name at all. It's not important or
different enough to be worth one. There are on three bells 3 possible
non-jump changes, on four bells 5, etc. It's just one of them and
needs its own name no more than does the maximus change with place
notation 36789T.

(Yes, for algebraic stuff the identity is sufficiently interesting
that it warrants its own name. And in the world of change ringing
rows, the pseudo-identity rounds is sufficiently interesting to
warrant its own name. But in the world of non-jump changes there is
nothing special about the identity change, and there'd be a whole lot
less wind spent if it just went around unlabeled. The most
interesting, individual non-jump changes are those at even stages with
place notations x and 1, which sort of get the names "cross" and
"hunt"; and at odd stages the various single changes, which don't get
their own names at all. Most changes, if they get labeled at all, just
get labeled by their place notation. So in doubles we have the change
12345, just like we have 125 and 145.)

--
Don Morrison <dfm at ringing.org>
"One of the unpardonable sins, in the eyes of most people, is for a
man to go about unlabeled. The world regards such a person as the
police do an unmuzzled dog, not under proper control."
-- T H Huxley, _Evoluton and Ethics_
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