vacancyCastleBB :: Colour -> Castle -> BitBoard
vacancyCastleBB White Long  =
  mconcat [ fromSquare sq
          | sq <- [(toSquare bFile firstRank) .. (toSquare dFile firstRank)]
          ]
vacancyCastleBB :: Colour -> Castle -> BitBoard
vacancyCastleBB White Long  =
  mconcat [ fromSquare sq
          | sq <- [(toSquare bFile firstRank) .. (toSquare dFile firstRank)]
          ]
vacancyCastleBB White Long  =
  mconcat [ fromSquare sq
          | sq <- [(toSquare bFile firstRank) .. (toSquare dFile firstRank)]
          ]