[r-t] applicability and timing (was The null change)

[Matthew Frye]

On 30 Dec 2014, at 16:19, Don Morrison <dfm at ringing.org> wrote:
> (modulo whatever the *&^$% a "plain course" is [for non-β-methods]).

I don't think we *need* to define this, but it might be nice to anyway. It surely must be either the method applied to rounds, or all of the sequences obtained by applying the method to the N! possible starting rows.

> - the decision is that it's got to move at least once per lead, it's
> less clear; it'll depend upon how we define "lead", I suppose. I think
> it could be easily made applicable to non-β methods, if we so chose.

I've been thinking about this. I might like something along the lines of "the method definition must make every bell to move at least once" as the only sane starting point (I think trying to discuss "courses" or "leads" in the context of non-β methods is a lost cause), but that needs some serious work. Apart from anything else, there's nothing to stop someone from adding in an obscure rule that would only be engaged by a row that will never be rung to artificially satisfy that requirement.

This is an important point, because there's no point applying the rule to all β-methods, if you can simulate such things trivially with non-β-methods which are not subject to the rule. *If* we want this rule, we will need either to prohibit non-β-methods, find a phrasing suitable to apply this rule sensibly to β-methods. I don't know how this could possibly be dealt with.

> Whether or not rotation is applicable to non-β methods I have no
> idea, though it sure does make my head ache to ponder it. Then again,
> even for β-methods rotation has demanded a lot of aspirin.

I feel that there is a rotation equivalent. e.g. something like "plain hunt but make 2nds when the 5 leads and 4ths when the 1 or 6 leads" would feel like a quasi-rotation of Dixon's Bob. Not a clue how to formalise this thought, unfortunately; would you pass the aspirin this way please...

MF