[r-t] The null change

[Matthew Frye]

On 30 Dec 2014, at 17:36, Don Morrison <dfm at ringing.org> wrote:
> On Tue, Dec 30, 2014 at 10:27 AM, Tim Barnes <tjbarnes23 at gmail.com> wrote:
>> let's start the debate on the null change.
> [...]
> 1) Is the null change even a part of change ringing? Put another way,
> when we define a "change" does that definition include the identity?
> 
> 2a) If the answer to (1) is "yes", can we use the null change in calls?
> 
> 2b) If the answer to (1) is "yes", can we use the null change in methods?
> 
> 3) If the answer to (2b) is "yes", can we use the null change in α-methods?
> 
> 4) If the answer to (3) is "yes", can we use the null change in β-methods?

For me, a change is a way to move between one row and the next row that is rung, if those two rows happen to be the same than you have the null change. I see no reason to arbitrarily prohibit a particular row from being one particular sequence of bells, so I can't see why it should be prohibited in its own right. It is, of course, rarely of practical use due to falseness, but it can be used if you ring more than an extent. I struggle to see why so many seem to have such a conceptual problem with this.

That seems to cover 1) and if it's part of change ringing, I can't see any reason to exclude it from being used in any of the parts of change ringing. To me, concerns about the null change should really be concerns about falseness (which I'm sure will be a thrilling discussion to be had sometime in the coming months).

> All the sequences of changes generated by a method must include at least
> one non-null change.

Do you really think that's necessary? Why not allow someone to define a methods composed entirely of null changes? If they can compose something true with it, then good on them!

> This would allow ringing things in whole pulls.

I'm not convinced that ringing things in whole pulls is the same as allowing use of the null change. To me, ringing in whole pulls says that you only apply a change every other stroke, whereas the null change implies you are indeed applying a change, it's just that you get the same row out as you were ringing before. In practical terms, you then also have a big issue over truth with whole-pull ringing - meaning you probably couldn't call anything with 7/8 or more bells true using null changes, but I see little conceptual difference between ringing 6 in whole pulls and ringing 8 in whole pulls (unless you insist on labelling it with null changes).

MF