+const int MAX_MOVES = 256;
+const int MAX_PLY = 120;
+const int MAX_PLY_PLUS_6 = MAX_PLY + 6;
+
+/// A move needs 16 bits to be stored
+///
+/// bit 0- 5: destination square (from 0 to 63)
+/// bit 6-11: origin square (from 0 to 63)
+/// bit 12-13: promotion piece type - 2 (from KNIGHT-2 to QUEEN-2)
+/// bit 14-15: special move flag: promotion (1), en passant (2), castling (3)
+/// NOTE: EN-PASSANT bit is set only when a pawn can be captured
+///
+/// Special cases are MOVE_NONE and MOVE_NULL. We can sneak these in because in
+/// any normal move destination square is always different from origin square
+/// while MOVE_NONE and MOVE_NULL have the same origin and destination square.
+
+enum Move {
+ MOVE_NONE,
+ MOVE_NULL = 65
+};
+
+enum MoveType {
+ NORMAL,
+ PROMOTION = 1 << 14,
+ ENPASSANT = 2 << 14,
+ CASTLING = 3 << 14
+};
+
+enum Color {
+ WHITE, BLACK, NO_COLOR, COLOR_NB = 2
+};
+
+enum CastlingSide {
+ KING_SIDE, QUEEN_SIDE, CASTLING_SIDE_NB = 2
+};
+
+enum CastlingRight { // Defined as in PolyGlot book hash key
+ NO_CASTLING,
+ WHITE_OO,
+ WHITE_OOO = WHITE_OO << 1,
+ BLACK_OO = WHITE_OO << 2,
+ BLACK_OOO = WHITE_OO << 3,
+ ANY_CASTLING = WHITE_OO | WHITE_OOO | BLACK_OO | BLACK_OOO,
+ CASTLING_RIGHT_NB = 16
+};
+
+template<Color C, CastlingSide S> struct MakeCastling {
+ static const CastlingRight
+ right = C == WHITE ? S == QUEEN_SIDE ? WHITE_OOO : WHITE_OO
+ : S == QUEEN_SIDE ? BLACK_OOO : BLACK_OO;
+};
+
+enum Phase {
+ PHASE_ENDGAME,
+ PHASE_MIDGAME = 128,
+ MG = 0, EG = 1, PHASE_NB = 2
+};
+
+enum ScaleFactor {
+ SCALE_FACTOR_DRAW = 0,
+ SCALE_FACTOR_ONEPAWN = 48,
+ SCALE_FACTOR_NORMAL = 64,
+ SCALE_FACTOR_MAX = 128,
+ SCALE_FACTOR_NONE = 255
+};