extern int SquareDistance[SQUARE_NB][SQUARE_NB];
const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
+const Bitboard TheirHalf[COLOR_NB] = { Rank5BB | Rank6BB | Rank7BB | Rank8BB,
+ Rank1BB | Rank2BB | Rank3BB | Rank4BB };
/// Overloads of bitwise operators between a Bitboard and a Square for testing
/// whether a given bit is set in a bitboard, and for setting and clearing bits.