Prolect/utilities.pl at main · Jashani/Prolect · GitHub

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:- [operators].

switch_colour(white, black).
switch_colour(black, white).

% Merge two lists of pieces
merge_pieces([], Pieces, Pieces).
merge_pieces(Pieces, [], Pieces).
merge_pieces([Piece1@X1/Y1 | Rest1], [Piece2@X2/Y2 | Rest2], Result) :-
    (Y1 < Y2;
    Y1 == Y2, X1 > X2),
    merge_pieces([Piece1@X1/Y1 | Rest1], Rest2, TempResult),
    Result = [Piece2@X2/Y2 | TempResult], !
    ;
    merge_pieces(Rest1, [Piece2@X2/Y2 | Rest2], TempResult),
    Result = [Piece1@X1/Y1 | TempResult], !.

% is_en_passant(+OpponentPieces, +Move, -VirtualPawnPosition)
% Checks if Move describes a pawn taking another pawn through "en passant",
% and returns the position of the taken pawn.
% Assumes Move is a valid move.
is_en_passant(OpponentPieces, pawn@X1/Y1 goto X2/Y2, X2/Y1) :-
    X1 =\= X2,
    \+ position_taken(X2/Y2, OpponentPieces).

% is_promotion(+Move)
% Checks if Move describes a pawn getting to the last rank and promotes.
% Assumes Move is a valid move.
is_promotion(pawn@_/_ goto _/Y2) :-
    Y2 = 1 ; Y2 = 8.

% apply_move(+(PlayerPieces vs OpponentPieces), +Move, -(NewPlayerPieces vs NewOpponentPieces))
% Make appropriate changes in player piece lists according to move.
apply_move(Pieces, nomove, Pieces).

apply_move(PlayerPieces vs OpponentPieces, pawn@Origin goto Position, NewPlayerPieces vs NewOpponentPieces) :-
    is_promotion(pawn@Origin goto Position), !,
    remove_piece(pawn@Origin, PlayerPieces, TempPlayerPieces),
    insert_piece(queen@Position, TempPlayerPieces, NewPlayerPieces),
    remove_piece(pawn@Position, OpponentPieces, NewOpponentPieces), !.

apply_move(PlayerPieces vs OpponentPieces, pawn@Origin goto Position, NewPlayerPieces vs NewOpponentPieces) :-
    is_en_passant(OpponentPieces, pawn@Origin goto Position, PawnRealPosition), !,
    remove_piece(pawn@Origin, PlayerPieces, TempPlayerPieces),
    insert_piece(pawn@Position, TempPlayerPieces, NewPlayerPieces),
    remove_piece(pawn@PawnRealPosition, OpponentPieces, NewOpponentPieces), !.

apply_move(PlayerPieces vs OpponentPieces, Type@Origin goto Position, NewPlayerPieces vs NewOpponentPieces) :-
    remove_piece(Type@Origin, PlayerPieces, TempPlayerPieces),
    insert_piece(Type@Position, TempPlayerPieces, NewPlayerPieces),
    remove_piece(_@Position, OpponentPieces, NewOpponentPieces), !.

% Insufficient material
draw([king@_] vs [king@_]).
draw([king@_, knight@_] vs [king@_]).
draw([king@_] vs [king@_, knight@_]).
draw([king@_, bishop@_] vs [king@_]).
draw([king@_] vs [king@_, bishop@_]).

check_game_end(PlayerPieces vs OpponentPieces, Color, LastMove, Outcome, EndScore) :-
	%write("check_game_end LastMove is: "), write(LastMove), nl,
	nonvar(LastMove), LastMove = nomove, !,
	(
		check(PlayerPieces vs OpponentPieces, Color, LastMove), !,
			%write("check_game_end about lose because of check with LastMove: "), write(LastMove), nl,
			Outcome = loss,
			lose_score(Color, EndScore)
			;
			%write("check_game_end about to draw because of: "), write(LastMove), nl,
			Outcome = draw,
			EndScore = 0
	)
	;
	king_dead(OpponentPieces), !,
	Outcome = win,
	win_score(Color, EndScore)
	;
	EndScore = 0,
	draw(PlayerPieces vs OpponentPieces), !,
	Outcome = draw
	;
	Outcome = play_on.

win_score(white, 9999).
win_score(black, -9999).
lose_score(white, Score) :-
	win_score(black, Score).
lose_score(black, Score) :-
	win_score(white, Score).

% Tragedy
king_dead(PlayerPieces) :-
    \+ member(king@_, PlayerPieces).