[r-t] delta based transposition for blue line generation

[Mark Davies]

Alan writes,

> Yes you could, but I think that probably just moves the special case
> into CCBRToPlace, which I use elsewhere as well.

Correct, but I think it's neater to deal with it there. It just needs to 
be a map from Char -> Option[Int]; a constant val better than a function 
in fact.

> The other issue is that
> it only really copes with the PN that's used on methods.ringing.org
> and could do with extending to cope with other variants as well.

I don't think you're far off that. The only thing you're obviously 
missing is the use of "x" for cross change, but that can easily be fixed 
in the CCBRToPlace map (if you collapse the special cases into there). 
Of course to deal with "full" place notations for symmetric leads you'll 
need some extra gubbins for the common & notation and other forms, but 
that to my mind sits outside of this bit of code.

MBD

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus