Probably best that I change the extra files to 'y' and 'z'.
Well, if it is important for backward compatibility you could keep the 'x' for Brouhaha, as I explained in the edit of my previous posting. I suppose there aren't many other variants where simple a-... file IDs would not be satisfactory. Perhaps Omega Chess.
I think that there is very little reason to ever use anything else than consecutive letters to indicate the files, so a general way to define arbitrary individual names seems like overdoing it. A satisfactory solution would be to define 'w' as the letter preceding 'a' (to avoid xyz), and count backwards through the alphabet when more-'negative' letters are needed. So for Brouhaha we would use 'w' and 'i', and could describe the system by specifying a simple offset (e.g. firstFile=w). Another possible system would be to define the number of 'extra files', which would be assumed added to the board proper both left and right, and would have their own system of letter assignment from near the end of the alphabet. The first file of the proper board would then always be 'a'.
Well, if it is important for backward compatibility you could keep the 'x' for Brouhaha, as I explained in the edit of my previous posting. I suppose there aren't many other variants where simple a-... file IDs would not be satisfactory. Perhaps Omega Chess.
I think that there is very little reason to ever use anything else than consecutive letters to indicate the files, so a general way to define arbitrary individual names seems like overdoing it. A satisfactory solution would be to define 'w' as the letter preceding 'a' (to avoid xyz), and count backwards through the alphabet when more-'negative' letters are needed. So for Brouhaha we would use 'w' and 'i', and could describe the system by specifying a simple offset (e.g. firstFile=w). Another possible system would be to define the number of 'extra files', which would be assumed added to the board proper both left and right, and would have their own system of letter assignment from near the end of the alphabet. The first file of the proper board would then always be 'a'.