+typedef uint64_t Bitboard;
+
+constexpr int MAX_MOVES = 256;
+constexpr int MAX_PLY = 128;
+
+/// 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 : int {
+ MOVE_NONE,
+ MOVE_NULL = 65
+};
+
+enum MoveType {
+ NORMAL,
+ PROMOTION = 1 << 14,
+ ENPASSANT = 2 << 14,
+ CASTLING = 3 << 14
+};
+
+enum Color {
+ WHITE, BLACK, COLOR_NB = 2
+};
+
+enum CastlingSide {
+ KING_SIDE, QUEEN_SIDE, CASTLING_SIDE_NB = 2
+};
+
+enum CastlingRight {
+ NO_CASTLING,
+ WHITE_OO,
+ WHITE_OOO = WHITE_OO << 1,
+ BLACK_OO = WHITE_OO << 2,
+ BLACK_OOO = WHITE_OO << 3,
+ WHITE_CASTLING = WHITE_OO | WHITE_OOO,
+ BLACK_CASTLING = BLACK_OO | BLACK_OOO,
+ ANY_CASTLING = WHITE_CASTLING | BLACK_CASTLING,
+ CASTLING_RIGHT_NB = 16
+};
+
+enum Phase {
+ PHASE_ENDGAME,
+ PHASE_MIDGAME = 128,
+ MG = 0, EG = 1, PHASE_NB = 2
+};
+
+enum ScaleFactor {
+ SCALE_FACTOR_DRAW = 0,
+ SCALE_FACTOR_NORMAL = 64,
+ SCALE_FACTOR_MAX = 128,
+ SCALE_FACTOR_NONE = 255
+};
+
+enum Bound {
+ BOUND_NONE,
+ BOUND_UPPER,
+ BOUND_LOWER,
+ BOUND_EXACT = BOUND_UPPER | BOUND_LOWER
+};
+
+enum Value : int {
+ VALUE_ZERO = 0,
+ VALUE_DRAW = 0,
+ VALUE_KNOWN_WIN = 10000,
+ VALUE_MATE = 32000,
+ VALUE_INFINITE = 32001,
+ VALUE_NONE = 32002,
+
+ VALUE_MATE_IN_MAX_PLY = VALUE_MATE - 2 * MAX_PLY,
+ VALUE_MATED_IN_MAX_PLY = -VALUE_MATE + 2 * MAX_PLY,
+
+ PawnValueMg = 136, PawnValueEg = 208,
+ KnightValueMg = 782, KnightValueEg = 865,
+ BishopValueMg = 830, BishopValueEg = 918,
+ RookValueMg = 1289, RookValueEg = 1378,
+ QueenValueMg = 2529, QueenValueEg = 2687,
+
+ MidgameLimit = 15258, EndgameLimit = 3915
+};
+
+enum PieceType {
+ NO_PIECE_TYPE, PAWN, KNIGHT, BISHOP, ROOK, QUEEN, KING,
+ ALL_PIECES = 0,
+ PIECE_TYPE_NB = 8
+};
+
+enum Piece {
+ NO_PIECE,
+ W_PAWN = 1, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
+ B_PAWN = 9, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING,
+ PIECE_NB = 16
+};
+
+extern Value PieceValue[PHASE_NB][PIECE_NB];
+
+enum Depth : int {
+
+ ONE_PLY = 1,
+
+ DEPTH_ZERO = 0 * ONE_PLY,
+ DEPTH_QS_CHECKS = 0 * ONE_PLY,
+ DEPTH_QS_NO_CHECKS = -1 * ONE_PLY,
+ DEPTH_QS_RECAPTURES = -5 * ONE_PLY,
+
+ DEPTH_NONE = -6 * ONE_PLY,
+ DEPTH_MAX = MAX_PLY * ONE_PLY
+};
+
+static_assert(!(ONE_PLY & (ONE_PLY - 1)), "ONE_PLY is not a power of 2");
+
+enum Square : int {
+ SQ_A1, SQ_B1, SQ_C1, SQ_D1, SQ_E1, SQ_F1, SQ_G1, SQ_H1,
+ SQ_A2, SQ_B2, SQ_C2, SQ_D2, SQ_E2, SQ_F2, SQ_G2, SQ_H2,
+ SQ_A3, SQ_B3, SQ_C3, SQ_D3, SQ_E3, SQ_F3, SQ_G3, SQ_H3,
+ SQ_A4, SQ_B4, SQ_C4, SQ_D4, SQ_E4, SQ_F4, SQ_G4, SQ_H4,
+ SQ_A5, SQ_B5, SQ_C5, SQ_D5, SQ_E5, SQ_F5, SQ_G5, SQ_H5,
+ SQ_A6, SQ_B6, SQ_C6, SQ_D6, SQ_E6, SQ_F6, SQ_G6, SQ_H6,
+ SQ_A7, SQ_B7, SQ_C7, SQ_D7, SQ_E7, SQ_F7, SQ_G7, SQ_H7,
+ SQ_A8, SQ_B8, SQ_C8, SQ_D8, SQ_E8, SQ_F8, SQ_G8, SQ_H8,
+ SQ_NONE,
+
+ SQUARE_NB = 64
+};
+
+enum Direction : int {
+ NORTH = 8,
+ EAST = 1,
+ SOUTH = -NORTH,
+ WEST = -EAST,
+
+ NORTH_EAST = NORTH + EAST,
+ SOUTH_EAST = SOUTH + EAST,
+ SOUTH_WEST = SOUTH + WEST,
+ NORTH_WEST = NORTH + WEST
+};
+
+enum File : int {
+ FILE_A, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_H, FILE_NB
+};
+
+enum Rank : int {
+ RANK_1, RANK_2, RANK_3, RANK_4, RANK_5, RANK_6, RANK_7, RANK_8, RANK_NB
+};
+
+
+/// Score enum stores a middlegame and an endgame value in a single integer (enum).
+/// The least significant 16 bits are used to store the middlegame value and the
+/// upper 16 bits are used to store the endgame value. We have to take care to
+/// avoid left-shifting a signed int to avoid undefined behavior.
+enum Score : int { SCORE_ZERO };
+
+constexpr Score make_score(int mg, int eg) {
+ return Score((int)((unsigned int)eg << 16) + mg);
+}
+
+/// Extracting the signed lower and upper 16 bits is not so trivial because
+/// according to the standard a simple cast to short is implementation defined
+/// and so is a right shift of a signed integer.
+inline Value eg_value(Score s) {
+ union { uint16_t u; int16_t s; } eg = { uint16_t(unsigned(s + 0x8000) >> 16) };
+ return Value(eg.s);
+}
+
+inline Value mg_value(Score s) {
+ union { uint16_t u; int16_t s; } mg = { uint16_t(unsigned(s)) };
+ return Value(mg.s);
+}
+
+#define ENABLE_BASE_OPERATORS_ON(T) \
+constexpr T operator+(T d1, T d2) { return T(int(d1) + int(d2)); } \
+constexpr T operator-(T d1, T d2) { return T(int(d1) - int(d2)); } \
+constexpr T operator-(T d) { return T(-int(d)); } \
+inline T& operator+=(T& d1, T d2) { return d1 = d1 + d2; } \
+inline T& operator-=(T& d1, T d2) { return d1 = d1 - d2; }
+
+#define ENABLE_INCR_OPERATORS_ON(T) \
+inline T& operator++(T& d) { return d = T(int(d) + 1); } \
+inline T& operator--(T& d) { return d = T(int(d) - 1); }
+
+#define ENABLE_FULL_OPERATORS_ON(T) \
+ENABLE_BASE_OPERATORS_ON(T) \
+ENABLE_INCR_OPERATORS_ON(T) \
+constexpr T operator*(int i, T d) { return T(i * int(d)); } \
+constexpr T operator*(T d, int i) { return T(int(d) * i); } \
+constexpr T operator/(T d, int i) { return T(int(d) / i); } \
+constexpr int operator/(T d1, T d2) { return int(d1) / int(d2); } \
+inline T& operator*=(T& d, int i) { return d = T(int(d) * i); } \
+inline T& operator/=(T& d, int i) { return d = T(int(d) / i); }
+
+ENABLE_FULL_OPERATORS_ON(Value)
+ENABLE_FULL_OPERATORS_ON(Depth)
+ENABLE_FULL_OPERATORS_ON(Direction)
+
+ENABLE_INCR_OPERATORS_ON(PieceType)
+ENABLE_INCR_OPERATORS_ON(Piece)
+ENABLE_INCR_OPERATORS_ON(Color)
+ENABLE_INCR_OPERATORS_ON(Square)
+ENABLE_INCR_OPERATORS_ON(File)
+ENABLE_INCR_OPERATORS_ON(Rank)
+
+ENABLE_BASE_OPERATORS_ON(Score)
+
+#undef ENABLE_FULL_OPERATORS_ON
+#undef ENABLE_INCR_OPERATORS_ON
+#undef ENABLE_BASE_OPERATORS_ON
+
+/// Additional operators to add integers to a Value
+constexpr Value operator+(Value v, int i) { return Value(int(v) + i); }
+constexpr Value operator-(Value v, int i) { return Value(int(v) - i); }
+inline Value& operator+=(Value& v, int i) { return v = v + i; }
+inline Value& operator-=(Value& v, int i) { return v = v - i; }
+
+/// Additional operators to add a Direction to a Square
+constexpr Square operator+(Square s, Direction d) { return Square(int(s) + int(d)); }
+constexpr Square operator-(Square s, Direction d) { return Square(int(s) - int(d)); }
+inline Square& operator+=(Square& s, Direction d) { return s = s + d; }
+inline Square& operator-=(Square& s, Direction d) { return s = s - d; }
+
+/// Only declared but not defined. We don't want to multiply two scores due to
+/// a very high risk of overflow. So user should explicitly convert to integer.
+Score operator*(Score, Score) = delete;
+
+/// Division of a Score must be handled separately for each term
+inline Score operator/(Score s, int i) {
+ return make_score(mg_value(s) / i, eg_value(s) / i);
+}
+
+/// Multiplication of a Score by an integer. We check for overflow in debug mode.
+inline Score operator*(Score s, int i) {
+
+ Score result = Score(int(s) * i);
+
+ assert(eg_value(result) == (i * eg_value(s)));
+ assert(mg_value(result) == (i * mg_value(s)));
+ assert((i == 0) || (result / i) == s);
+
+ return result;
+}
+
+constexpr Color operator~(Color c) {
+ return Color(c ^ BLACK); // Toggle color
+}
+
+constexpr Square operator~(Square s) {
+ return Square(s ^ SQ_A8); // Vertical flip SQ_A1 -> SQ_A8
+}
+
+constexpr File operator~(File f) {
+ return File(f ^ FILE_H); // Horizontal flip FILE_A -> FILE_H
+}
+
+constexpr Piece operator~(Piece pc) {
+ return Piece(pc ^ 8); // Swap color of piece B_KNIGHT -> W_KNIGHT
+}
+
+constexpr CastlingRight operator|(Color c, CastlingSide s) {
+ return CastlingRight(WHITE_OO << ((s == QUEEN_SIDE) + 2 * c));
+}
+
+constexpr Value mate_in(int ply) {
+ return VALUE_MATE - ply;
+}
+
+constexpr Value mated_in(int ply) {
+ return -VALUE_MATE + ply;
+}
+
+constexpr Square make_square(File f, Rank r) {
+ return Square((r << 3) + f);
+}
+
+constexpr Piece make_piece(Color c, PieceType pt) {
+ return Piece((c << 3) + pt);
+}
+
+constexpr PieceType type_of(Piece pc) {
+ return PieceType(pc & 7);
+}
+
+inline Color color_of(Piece pc) {
+ assert(pc != NO_PIECE);
+ return Color(pc >> 3);
+}
+
+constexpr bool is_ok(Square s) {
+ return s >= SQ_A1 && s <= SQ_H8;
+}
+
+constexpr File file_of(Square s) {
+ return File(s & 7);
+}
+
+constexpr Rank rank_of(Square s) {
+ return Rank(s >> 3);
+}
+
+constexpr Square relative_square(Color c, Square s) {
+ return Square(s ^ (c * 56));
+}
+
+constexpr Rank relative_rank(Color c, Rank r) {
+ return Rank(r ^ (c * 7));
+}
+
+constexpr Rank relative_rank(Color c, Square s) {
+ return relative_rank(c, rank_of(s));
+}
+
+constexpr Direction pawn_push(Color c) {
+ return c == WHITE ? NORTH : SOUTH;
+}
+
+constexpr Square from_sq(Move m) {
+ return Square((m >> 6) & 0x3F);
+}
+
+constexpr Square to_sq(Move m) {
+ return Square(m & 0x3F);
+}
+
+constexpr int from_to(Move m) {
+ return m & 0xFFF;
+}
+
+constexpr MoveType type_of(Move m) {
+ return MoveType(m & (3 << 14));
+}
+
+constexpr PieceType promotion_type(Move m) {
+ return PieceType(((m >> 12) & 3) + KNIGHT);
+}
+
+constexpr Move make_move(Square from, Square to) {
+ return Move((from << 6) + to);
+}
+
+template<MoveType T>
+constexpr Move make(Square from, Square to, PieceType pt = KNIGHT) {
+ return Move(T + ((pt - KNIGHT) << 12) + (from << 6) + to);
+}
+
+constexpr bool is_ok(Move m) {
+ return from_sq(m) != to_sq(m); // Catch MOVE_NULL and MOVE_NONE
+}