+constexpr Bitboard make_bitboard() { return 0; }
+
+template<typename ...Squares>
+constexpr Bitboard make_bitboard(Square s, Squares... squares) {
+ return (1ULL << s) | make_bitboard(squares...);
+}
+
+
+/// shift() moves a bitboard one step along direction D (mainly for pawns)
+
+template<Direction D>
+constexpr Bitboard shift(Bitboard b) {
+ return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
+ : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == SOUTH_EAST ? (b & ~FileHBB) >> 7
+ : D == NORTH_WEST ? (b & ~FileABB) << 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
+ : 0;
+}
+
+
+/// pawn_attacks_bb() returns the pawn attacks for the given color from the
+/// squares in the given bitboard.
+
+template<Color C>
+constexpr Bitboard pawn_attacks_bb(Bitboard b) {
+ return C == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)
+ : shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);