You are mixing XBetza with bracket notation. You cannot do that; a in bracket notation would mean 'all directions', not continuation. You should have written [R?uW-cW-bpW-fW].
But your original [R?ufW-cfW-bD] is wrong in the first place. It specifies an unload on the start square of two consecutive W steps, and then a D step back. Which would end up on the same square as the unload. What you really want after the Rook move is step to the unload square (fmW), from there swap with the enemy piece (fucW) and step two back (bD). That is [R?W-ucW-bD]. (But note that this makes the attarction of the enemy piece optional; it could stop after R even if there is an enemy piece two steps further.) The D step would have to be split up in XBetza, and not being a 2nd leg the bracket preprocessor won't do that automatically. But it probably would handle [R?W-ucW-bpW-W] correctly.
[R?uW-cW-bpafW]
You are mixing XBetza with bracket notation. You cannot do that; a in bracket notation would mean 'all directions', not continuation. You should have written [R?uW-cW-bpW-fW].
But your original [R?ufW-cfW-bD] is wrong in the first place. It specifies an unload on the start square of two consecutive W steps, and then a D step back. Which would end up on the same square as the unload. What you really want after the Rook move is step to the unload square (fmW), from there swap with the enemy piece (fucW) and step two back (bD). That is [R?W-ucW-bD]. (But note that this makes the attarction of the enemy piece optional; it could stop after R even if there is an enemy piece two steps further.) The D step would have to be split up in XBetza, and not being a 2nd leg the bracket preprocessor won't do that automatically. But it probably would handle [R?W-ucW-bpW-W] correctly.