template<typename ...PieceTypes> Bitboard pieces(PieceType pt, PieceTypes... pts) const;
Bitboard pieces(Color c) const;
template<typename ...PieceTypes> Bitboard pieces(Color c, PieceTypes... pts) const;
template<typename ...PieceTypes> Bitboard pieces(PieceType pt, PieceTypes... pts) const;
Bitboard pieces(Color c) const;
template<typename ...PieceTypes> Bitboard pieces(Color c, PieceTypes... pts) const;