💡📝H. G. Muller wrote on Mon, Jul 18, 2022 02:50 PM UTC:
For now I have solved this as follows: when a move is indicated as an initial one, it will still be rejected if the mover is not virgin. But if it is, it will be tested whether the mover is in an array inocheck, which by default is set to (K k). If it is, this will add the origin of the move to the set of e.p. squares. And hence consider it illegal if that square is under attack after the move. If you want to forbid any other piece to use inital moves when attacked, or when your royal does not have the label K, or you have multiple royal types, you could set the inocheck array to contain the types you desire.
As dicussed this can in theory fail in the presence of hoppers. Although it is extremely unlikely that you would ever want to play an initial move designed to get you to safety to stay in the path of a hopper. Anyway, it seems to solve the problem with the game you mentioned, as this now says 'checkmate!' above the board. It is also not possible to have both initial moves that can, and that cannot move out of check on the same piece.
About your implementation of that preset: it is not necessary to build the in-check dependence into the move list of the King that is used when the argumet to the K or k function is 0. This call only has to generate moves with an implied side effect, i.e. a change of the board state not explicitly expressed in the move eneterd by the user. This is used when playing out the moves of the game for the purpose of setting up the current position, to make sure the side effects are properly applied, but where there is no need for testing the (pseudo-)legality of the moves. As this would presumably have been done before the move was allowed to be appended to the game. Normally the only moves that do have side effects are e.p. capture and castling. So there is no need to generate other initial King moves than castling in that case; the extra moves you defined do not have side effects.
For now I have solved this as follows: when a move is indicated as an initial one, it will still be rejected if the mover is not virgin. But if it is, it will be tested whether the mover is in an array inocheck, which by default is set to (K k). If it is, this will add the origin of the move to the set of e.p. squares. And hence consider it illegal if that square is under attack after the move. If you want to forbid any other piece to use inital moves when attacked, or when your royal does not have the label K, or you have multiple royal types, you could set the inocheck array to contain the types you desire.
As dicussed this can in theory fail in the presence of hoppers. Although it is extremely unlikely that you would ever want to play an initial move designed to get you to safety to stay in the path of a hopper. Anyway, it seems to solve the problem with the game you mentioned, as this now says 'checkmate!' above the board. It is also not possible to have both initial moves that can, and that cannot move out of check on the same piece.
About your implementation of that preset: it is not necessary to build the in-check dependence into the move list of the King that is used when the argumet to the K or k function is 0. This call only has to generate moves with an implied side effect, i.e. a change of the board state not explicitly expressed in the move eneterd by the user. This is used when playing out the moves of the game for the purpose of setting up the current position, to make sure the side effects are properly applied, but where there is no need for testing the (pseudo-)legality of the moves. As this would presumably have been done before the move was allowed to be appended to the game. Normally the only moves that do have side effects are e.p. capture and castling. So there is no need to generate other initial King moves than castling in that case; the extra moves you defined do not have side effects.