Why use aa when you could use ab? In Betza notation directional modifiers indicating direction sets with an empty intersection means one or the other, and a and b do not have moves in common.
Problem is that this possibility does not exist in the XBetza 'a' notation, and that currently the bracket notation is first converted to an XBetza string before it is parsed. No matter what method you would use to indicate 'all directions including back', it could not be implemented by substitution of the modifier sequence by something else; it would require duplication of the string. If there would be an independent bracket-notation parser, this would come automatically. So we should simply wait for that, and this is yet another incentive to work on it.
Why use aa when you could use ab? In Betza notation directional modifiers indicating direction sets with an empty intersection means one or the other, and a and b do not have moves in common.
Problem is that this possibility does not exist in the XBetza 'a' notation, and that currently the bracket notation is first converted to an XBetza string before it is parsed. No matter what method you would use to indicate 'all directions including back', it could not be implemented by substitution of the modifier sequence by something else; it would require duplication of the string. If there would be an independent bracket-notation parser, this would come automatically. So we should simply wait for that, and this is yet another incentive to work on it.