Chess player
In the early times, chess used to be the prime example of artificial intelligence. Nowadays, some chess programs can beat a human master, and simple implementations can be written in a few pages of code.
Chess player is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Write a program which plays chess against a human player.
No need for graphics -- a textual user interface is sufficient.
Rather than implementing a complete monolithic program, you may wish to tackle one of the simpler sub-tasks:
- Chess player/Move generation
- Chess player/Search and evaluation
- Chess player/Program options and user interface
or use those components as part of a complete program, demonstrating your language's support for modularity.
Tony Marsland's computer chess player Awit is written in ALGOL W.
El código es de Dean Menezes
Encontrado en: http://www.petesqbsite.com/sections/express/issue23/Tut_QB_Chess.txt
DEFINT A-Z
DECLARE SUB SQUARE (A, B, C)
DECLARE SUB SHOWMAN (A, B, FLAG)
DECLARE SUB SHOWBD ()
DECLARE SUB IO (A, B, X, Y, RESULT)
DECLARE FUNCTION INCHECK (X)
DECLARE SUB MAKEMOVE (A, B, X, Y)
DECLARE SUB KNIGHT (A, B, XX(), YY(), NDX)
DECLARE SUB KING (A, B, XX(), YY(), NDX)
DECLARE SUB QUEEN (A, B, XX(), YY(), NDX)
DECLARE SUB ROOK (A, B, XX(), YY(), NDX)
DECLARE SUB BISHOP (A, B, XX(), YY(), NDX)
DECLARE SUB MOVELIST (A, B, XX(), YY(), NDX)
DECLARE SUB PAWN (A, B, XX(), YY(), NDX)
DECLARE FUNCTION EVALUATE (ID, PRUNE)
DIM SHARED BOARD(0 TO 7, 0 TO 7)
DIM SHARED BESTA(0 TO 7), BESTB(0 TO 7), BESTX(0 TO 7), BESTY(0 TO 7)
DIM SHARED LEVEL, MAXLEVEL, SCORE, CFLAG
CFLAG = 0
LEVEL = 0
MAXLEVEL = 5
DATA -500,-270,-300,-900,-7500,-300,-270,-500
DATA -100,-100,-100,-100, -100,-100,-100,-100
DATA 0, 0, 0, 0, 0, 0, 0, 0
DATA 0, 0, 0, 0, 0, 0, 0, 0
DATA 0, 0, 0, 0, 0, 0, 0, 0
DATA 0, 0, 0, 0, 0, 0, 0, 0
DATA 100, 100, 100, 100, 100, 100, 100, 100
DATA 500, 270, 300, 900, 5000, 300, 270, 500
FOR X = 0 TO 7
FOR Y = 0 TO 7
READ Z
BOARD(X, Y) = Z
NEXT Y
NEXT X
A = -1
RESULT = 0
DO
SCORE = 0
CALL IO(A, B, X, Y, RESULT)
CLS
CALL SHOWBD
RESULT = EVALUATE(-1, 10000)
A = BESTA(1)
B = BESTB(1)
X = BESTX(1)
Y = BESTY(1)
LOOP
end
SUB BISHOP (A, B, XX(), YY(), NDX)
ID = SGN(BOARD(B, A))
FOR DXY = 1 TO 7
X = A - DXY
Y = B + DXY
IF X < 0 OR X > 7 OR Y < 0 OR Y > 7 THEN EXIT FOR
GOSUB 3
IF BOARD(Y, X) THEN EXIT FOR
NEXT
FOR DXY = 1 TO 7
X = A + DXY
Y = B + DXY
IF X < 0 OR X > 7 OR Y < 0 OR Y > 7 THEN EXIT FOR
GOSUB 3
IF BOARD(Y, X) THEN EXIT FOR
NEXT
FOR DXY = 1 TO 7
X = A - DXY
Y = B - DXY
IF X < 0 OR X > 7 OR Y < 0 OR Y > 7 THEN EXIT FOR
GOSUB 3
IF BOARD(Y, X) THEN EXIT FOR
NEXT
FOR DXY = 1 TO 7
X = A + DXY
Y = B - DXY
IF X < 0 OR X > 7 OR Y < 0 OR Y > 7 THEN EXIT FOR
GOSUB 3
IF BOARD(Y, X) THEN EXIT FOR
NEXT
EXIT SUB
3 REM
IF ID <> SGN(BOARD(Y, X)) THEN
NDX = NDX + 1
XX(NDX) = X
YY(NDX) = Y
END IF
RETURN
END SUB
FUNCTION EVALUATE (ID, PRUNE)
DIM XX(0 TO 26), YY(0 TO 26)
LEVEL = LEVEL + 1
BESTSCORE = 10000 * ID
FOR B = 7 TO 0 STEP -1
FOR A = 7 TO 0 STEP -1
IF SGN(BOARD(B, A)) <> ID THEN GOTO 1
IF (LEVEL = 1) THEN CALL SHOWMAN(A, B, 8)
CALL MOVELIST(A, B, XX(), YY(), NDX)
FOR I = 0 TO NDX
X = XX(I)
Y = YY(I)
IF LEVEL = 1 THEN
LOCATE 1, 1
PRINT "TRYING: "; CHR$(65 + A); 8 - B; "- "; CHR$(65 + X); 8 - Y
CALL SHOWMAN(X, Y, 8)
END IF
OLDSCORE = SCORE
MOVER = BOARD(B, A)
TARGET = BOARD(Y, X)
CALL MAKEMOVE(A, B, X, Y)
IF (LEVEL < MAXLEVEL) THEN SCORE = SCORE + EVALUATE(-ID, BESTSCORE - TARGET + ID * (8 - ABS(4 - X) - ABS(4 - Y)))
SCORE = SCORE + TARGET - ID * (8 - ABS(4 - X) - ABS(4 - Y))
IF (ID < 0 AND SCORE > BESTSCORE) OR (ID > 0 AND SCORE < BESTSCORE) THEN
BESTA(LEVEL) = A
BESTB(LEVEL) = B
BESTX(LEVEL) = X
BESTY(LEVEL) = Y
BESTSCORE = SCORE
IF (ID < 0 AND BESTSCORE >= PRUNE) OR (ID > 0 AND BESTSCORE <= PRUNE) THEN
BOARD(B, A) = MOVER
BOARD(Y, X) = TARGET
SCORE = OLDSCORE
IF (LEVEL = 1) THEN CALL SHOWMAN(X, Y, 0)
IF (LEVEL = 1) THEN CALL SHOWMAN(A, B, 0)
LEVEL = LEVEL - 1
EVALUATE = BESTSCORE
EXIT FUNCTION
END IF
END IF
BOARD(B, A) = MOVER
BOARD(Y, X) = TARGET
SCORE = OLDSCORE
IF (LEVEL = 1) THEN CALL SHOWMAN(X, Y, 0)
NEXT
1
IF (LEVEL = 1) THEN CALL SHOWMAN(A, B, 0)
NEXT
NEXT
LEVEL = LEVEL - 1
EVALUATE = BESTSCORE
END FUNCTION
FUNCTION INCHECK (X)
DIM XX(27), YY(27), NDX
FOR B = 0 TO 7
FOR A = 0 TO 7
IF BOARD(B, A) >= 0 THEN GOTO 6
CALL MOVELIST(A, B, XX(), YY(), NDX)
FOR I = 0 TO NDX STEP 1
X = XX(I)
Y = YY(I)
IF BOARD(Y, X) = 5000 THEN
PRINT "YOU ARE IN CHECK!"
PRINT " "
PRINT " "
INCHECK = 1
EXIT FUNCTION
END IF
NEXT
6 '
NEXT
NEXT
INCHECK = 0
END FUNCTION
SUB IO (A, B, X, Y, RESULT)
DIM XX(0 TO 26), YY(0 TO 26)
CLS
IF A >= 0 THEN
IF RESULT < -2500 THEN
PRINT "I RESIGN"
SLEEP
SYSTEM
END IF
PIECE = BOARD(Y, X)
CALL MAKEMOVE(A, B, X, Y)
PRINT "MY MOVE: "; CHR$(65 + A); 8 - B; "- "; CHR$(65 + X); 8 - Y
IF PIECE THEN
PRINT "I TOOK YOUR ";
IF PIECE = 100 THEN PRINT "PAWN"
IF PIECE = 270 THEN PRINT "KNIGHT"
IF PIECE = 300 THEN PRINT "BISHOP"
IF PIECE = 500 THEN PRINT "ROOK"
IF PIECE = 900 THEN PRINT "QUEEN"
IF PIECE = 5000 THEN PRINT "KING"
END IF
NULL = INCHECK(0)
END IF
DO
CALL SHOWBD
LOCATE 24, 1
INPUT "YOUR MOVE: ", IN$
IF UCASE$(IN$) = "QUIT" THEN CLS : END
IF UCASE$(IN$) = "O-O" OR IN$ = "0-0" THEN
IF CFLAG THEN GOTO 16
IF BOARD(7, 7) <> 500 THEN GOTO 16
IF BOARD(7, 6) OR BOARD(7, 5) THEN GOTO 16
BOARD(7, 6) = 5000
BOARD(7, 4) = 0
BOARD(7, 5) = 500
BOARD(7, 7) = 0
CFLAG = 1
EXIT SUB
END IF
IF UCASE$(IN$) = "O-O-O" OR IN$ = "0-0-0" THEN
IF CFLAG THEN GOTO 16
IF BOARD(7, 0) <> 500 THEN GOTO 16
IF BOARD(7, 1) OR BOARD(7, 2) OR BOARD(7, 3) THEN GOTO 16
BOARD(7, 2) = 5000
BOARD(7, 4) = 0
BOARD(7, 3) = 500
BOARD(7, 0) = 0
CFLAG = 1
EXIT SUB
END IF
IF LEN(IN$) < 5 THEN GOTO 16
B = 8 - (ASC(MID$(IN$, 2, 1)) - 48)
A = ASC(UCASE$(MID$(IN$, 1, 1))) - 65
X = ASC(UCASE$(MID$(IN$, 4, 1))) - 65
Y = 8 - (ASC(MID$(IN$, 5, 1)) - 48)
IF B > 7 OR B < 0 OR A > 7 OR A < 0 OR X > 7 OR X < 0 OR Y > 7 OR Y < 0 THEN GOTO 16
IF BOARD(B, A) <= 0 THEN GOTO 16
CALL MOVELIST(A, B, XX(), YY(), NDX)
FOR K = 0 TO NDX STEP 1
IF X = XX(K) AND Y = YY(K) THEN
MOVER = BOARD(B, A)
TARGET = BOARD(Y, X)
CALL MAKEMOVE(A, B, X, Y)
LOCATE 1, 1
IF INCHECK(0) = 0 THEN EXIT SUB
BOARD(B, A) = MOVER
BOARD(Y, X) = TARGET
GOTO 16
END IF
NEXT
16 '
CLS
LOOP
END SUB
SUB KING (A, B, XX(), YY(), NDX)
ID = SGN(BOARD(B, A))
FOR DY = -1 TO 1
IF B + DY < 0 OR B + DY > 7 THEN GOTO 12
FOR DX = -1 TO 1
IF A + DX < 0 OR A + DX > 7 THEN GOTO 11
IF ID <> SGN(BOARD(B + DY, A + DX)) THEN
NDX = NDX + 1
XX(NDX) = A + DX
YY(NDX) = B + DY
END IF
11 '
NEXT
12 '
NEXT
END SUB
SUB KNIGHT (A, B, XX(), YY(), NDX)
ID = SGN(BOARD(B, A))
X = A - 1
Y = B - 2
GOSUB 5
X = A - 2
Y = B - 1
GOSUB 5
X = A + 1
Y = B - 2
GOSUB 5
X = A + 2
Y = B - 1
GOSUB 5
X = A - 1
Y = B + 2
GOSUB 5
X = A - 2
Y = B + 1
GOSUB 5
X = A + 1
Y = B + 2
GOSUB 5
X = A + 2
Y = B + 1
GOSUB 5
EXIT SUB
5 '
IF X < 0 OR X > 7 OR Y < 0 OR Y > 7 THEN RETURN
IF ID <> SGN(BOARD(Y, X)) THEN NDX = NDX + 1: XX(NDX) = X: YY(NDX) = Y
RETURN
END SUB
SUB MAKEMOVE (A, B, X, Y)
BOARD(Y, X) = BOARD(B, A)
BOARD(B, A) = 0
IF Y = 0 AND BOARD(Y, X) = 100 THEN BOARD(Y, X) = 900
IF Y = 7 AND BOARD(Y, X) = -100 THEN BOARD(Y, X) = -900
END SUB
SUB MOVELIST (A, B, XX(), YY(), NDX)
PIECE = INT(ABS(BOARD(B, A)))
NDX = -1
IF PIECE = 100 THEN
CALL PAWN(A, B, XX(), YY(), NDX)
ELSEIF PIECE = 270 THEN CALL KNIGHT(A, B, XX(), YY(), NDX)
ELSEIF PIECE = 300 THEN CALL BISHOP(A, B, XX(), YY(), NDX)
ELSEIF PIECE = 500 THEN CALL ROOK(A, B, XX(), YY(), NDX)
ELSEIF PIECE = 900 THEN CALL QUEEN(A, B, XX(), YY(), NDX)
ELSE CALL KING(A, B, XX(), YY(), NDX)
END IF
END SUB
SUB PAWN (A, B, XX(), YY(), NDX)
ID = SGN(BOARD(B, A))
IF (A - 1) >= 0 AND (A - 1) <= 7 AND (B - ID) >= 0 AND (B - ID) <= 7 THEN
IF SGN(BOARD((B - ID), (A - 1))) = -ID THEN
NDX = NDX + 1
XX(NDX) = A - 1
YY(NDX) = B - ID
END IF
END IF
IF (A + 1) >= 0 AND (A + 1) <= 7 AND (B - ID) >= 0 AND (B - ID) <= 7 THEN
IF SGN(BOARD((B - ID), (A + 1))) = -ID THEN
NDX = NDX + 1
XX(NDX) = A + 1
YY(NDX) = B - ID
END IF
END IF
IF A >= 0 AND A <= 7 AND (B - ID) >= 0 AND (B - ID) <= 7 THEN
IF BOARD((B - ID), A) = 0 THEN
NDX = NDX + 1
XX(NDX) = A
YY(NDX) = B - ID
IF (ID < 0 AND B = 1) OR (ID > 0 AND B = 6) THEN
IF BOARD((B - ID - ID), A) = 0 THEN
NDX = NDX + 1
XX(NDX) = A
YY(NDX) = B - 2 * ID
END IF
END IF
END IF
END IF
END SUB
SUB QUEEN (A, B, XX(), YY(), NDX)
CALL BISHOP(A, B, XX(), YY(), NDX)
CALL ROOK(A, B, XX(), YY(), NDX)
END SUB
SUB ROOK (A, B, XX(), YY(), NDX)
ID = SGN(BOARD(B, A))
FOR X = A - 1 TO 0 STEP -1
IF ID <> SGN(BOARD(B, X)) THEN
NDX = NDX + 1
XX(NDX) = X
YY(NDX) = B
END IF
IF (BOARD(B, X)) THEN EXIT FOR
NEXT
FOR X = A + 1 TO 7 STEP 1
IF ID <> SGN(BOARD(B, X)) THEN
NDX = NDX + 1
XX(NDX) = X
YY(NDX) = B
END IF
IF (BOARD(B, X)) THEN EXIT FOR
NEXT
FOR Y = B - 1 TO 0 STEP -1
IF ID <> SGN(BOARD(Y, A)) THEN
NDX = NDX + 1
XX(NDX) = A
YY(NDX) = Y
END IF
IF (BOARD(Y, A)) THEN EXIT FOR
NEXT
FOR Y = B + 1 TO 7 STEP 1
IF ID <> SGN(BOARD(Y, A)) THEN
NDX = NDX + 1
XX(NDX) = A
YY(NDX) = Y
END IF
IF (BOARD(Y, A)) THEN EXIT FOR
NEXT
END SUB
SUB SHOWBD
LOCATE 3, 30
COLOR 7, 0
PRINT "A B C D E F G H"
FOR K = 0 TO 25
LOCATE 4, 28 + K
COLOR 6, 0
PRINT CHR$(220)
NEXT
FOR B = 0 TO 7
LOCATE 2 * B + 5, 26
COLOR 7, 0
PRINT CHR$(56 - B)
LOCATE 2 * B + 5, 28
COLOR 6, 0
PRINT CHR$(219)
LOCATE 2 * B + 6, 28
COLOR 6, 0
PRINT CHR$(219)
FOR A = 0 TO 7
IF ((A + B) MOD 2) THEN
COLOUR = 8
ELSE COLOUR = 12
END IF
CALL SQUARE(3 * A + 31, 2 * B + 5, COLOUR)
NEXT
LOCATE 2 * B + 5, 53
COLOR 6, 0
PRINT CHR$(219)
LOCATE 2 * B + 6, 53
COLOR 6, 0
PRINT CHR$(219)
LOCATE 2 * B + 6, 55
COLOR 7, 0
PRINT CHR$(56 - B)
NEXT
FOR K = 0 TO 25
LOCATE 21, 28 + K
COLOR 6, 0
PRINT CHR$(223)
NEXT
LOCATE 22, 30
COLOR 7, 0
PRINT "A B C D E F G H"
FOR B = 0 TO 7
FOR A = 0 TO 7
CALL SHOWMAN(A, B, 0)
NEXT
NEXT
COLOR 7, 0
END SUB
SUB SHOWMAN (A, B, FLAG)
IF BOARD(B, A) < 0 THEN BACK = 0
IF BOARD(B, A) > 0 THEN BACK = 7
FORE = 7 - BACK + FLAG
IF BOARD(B, A) = 0 THEN
IF (A + B) AND 1 THEN BACK = 8 ELSE BACK = 12
FORE = BACK + -1 * (FLAG > 0)
END IF
N$ = " "
PIECE = INT(ABS(BOARD(B, A)))
IF PIECE = 0 THEN N$ = CHR$(219)
IF PIECE = 100 THEN N$ = "P"
IF PIECE = 270 THEN N$ = "N"
IF PIECE = 300 THEN N$ = "B"
IF PIECE = 500 THEN N$ = "R"
IF PIECE = 900 THEN N$ = "Q"
IF PIECE = 5000 OR PIECE = 7500 THEN N$ = "K"
LOCATE 2 * B + 5 - (BOARD(B, A) > 0), 3 * A + 30
COLOR FORE, BACK
PRINT N$
LOCATE 1, 1
COLOR 7, 0
END SUB
SUB SQUARE (A, B, C)
MT$ = CHR$(219)
MT$ = MT$ + MT$ + MT$
LOCATE B, A - 2
COLOR C, C
PRINT MT$
LOCATE B + 1, A - 2
COLOR C, C
PRINT MT$
COLOR 7, 0
END SUB
This is an open source chess program written in FreeBASIC that I found on Github FreeBasicChess.
There are a number of open source Chess programs written in Go on Github.
Rather than spend a lot of time trying to write my own (likely mediocre) program, I thought I'd simply post a link to notnil/chess which explains its various capabilities quite well. However, you need to look at the code itself to see that it can cope with all types of move including castling, en passant capture and promotion to a piece of the player's choice.
import java.util.*;
// Main class for testing
class ChessEngine {
public static void testChess() {
// Position with check
String fenCheck = "4k3/8/8/7Q/8/8/8/4K3 b - - 0 1";
Board boardCheck = Board.parseFEN(fenCheck);
System.out.println("--- Position with Black in Check ---");
boardCheck.print();
System.out.println("\nIs Black king in check? " + boardCheck.inCheck('b'));
List<Move> movesCheck = boardCheck.getLegalMoves();
System.out.println("\nLegal moves for Black (to get out of check or make other moves):");
// Starting position
String fenStart = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
Board boardStart = Board.parseFEN(fenStart);
System.out.println("--- Starting Position ---");
boardStart.print();
List<Move> movesStart = boardStart.getLegalMoves();
System.out.println("\nLegal moves for Black (to get out of check or make other moves):");
if (movesCheck.isEmpty()) {
System.out.println("No legal moves. (This might indicate checkmate or stalemate)");
} else {
for (Move move : movesCheck) {
System.out.println("- " + move);
}
}
System.out.println("Total legal moves: " + movesCheck.size());
System.out.println("\n" + "=".repeat(40) + "\n");
// Mid-game position
String fenMidgame = "r3k2r/p1ppqpb1/bn2pn1p/3PP1p1/1p2P3/2N2N2/PPPBBPPP/R2QK2R w KQkq - 0 1";
Board boardMidgame = Board.parseFEN(fenMidgame);
System.out.println("--- Mid-game Position (White to move) ---");
boardMidgame.print();
List<Move> movesMidgame = boardMidgame.getLegalMoves();
System.out.println("\nLegal moves for White:");
if (movesMidgame.isEmpty()) {
System.out.println("No legal moves.");
} else {
for (Move move : movesMidgame) {
System.out.println("- " + move);
}
}
System.out.println("Total legal moves: " + movesMidgame.size());
System.out.println("\n" + "=".repeat(40) + "\n");
// Castling position
String fenCastlingWhite = "r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1";
Board boardCastlingWhite = Board.parseFEN(fenCastlingWhite);
System.out.println("--- Position Allowing White Castling ---");
boardCastlingWhite.print();
List<Move> movesCastlingWhite = boardCastlingWhite.getLegalMoves();
System.out.println("\nLegal moves for White (including castling):");
if (movesCastlingWhite.isEmpty()) {
System.out.println("No legal moves.");
} else {
for (Move move : movesCastlingWhite) {
System.out.println("- " + move);
}
}
System.out.println("Total legal moves: " + movesCastlingWhite.size());
System.out.println("\n" + "=".repeat(40) + "\n");
// Pawn promotion position
String fenPromotion = "8/4P2k/8/8/8/8/8/R3K2R w KQkq - 0 1";
Board boardPromotion = Board.parseFEN(fenPromotion);
System.out.println("--- Position Allowing Pawn Promotion ---");
boardPromotion.print();
List<Move> movesPromotion = boardPromotion.getLegalMoves();
System.out.println("\nLegal moves for White (including pawn promotions):");
if (movesPromotion.isEmpty()) {
System.out.println("No legal moves.");
} else {
for (Move move : movesPromotion) {
System.out.println("- " + move);
}
}
System.out.println("Total legal moves: " + movesPromotion.size());
System.out.println("\n" + "=".repeat(40) + "\n");
// En passant position
String fenEnpassant = "rnbqkbnr/ppp1p1pp/8/3pPp2/8/8/PPPP1PPP/RNBQKBNR w KQkq f6 0 3";
Board boardEnpassant = Board.parseFEN(fenEnpassant);
System.out.println("--- Position Allowing En Passant ---");
boardEnpassant.print();
List<Move> movesEnpassant = boardEnpassant.getLegalMoves();
System.out.println("\nLegal moves for White (including en passant capture):");
if (movesEnpassant.isEmpty()) {
System.out.println("No legal moves.");
} else {
for (Move move : movesEnpassant) {
System.out.println("- " + move);
}
}
System.out.println("Total legal moves: " + movesEnpassant.size());
System.out.println("\n" + "=".repeat(40) + "\n");
// Stalemate position
String fenStalemate = "8/8/8/8/8/6k1/5b2/7K w - - 12 95";
Board boardStalemate = Board.parseFEN(fenStalemate);
System.out.println("--- Stalemate Position ---");
boardStalemate.print();
List<Move> movesStalemate = boardStalemate.getLegalMoves();
System.out.println("\nLegal moves for White (should be none):");
if (movesStalemate.isEmpty()) {
System.out.println("No legal moves. (This indicates stalemate)");
} else {
for (Move move : movesStalemate) {
System.out.println("- " + move);
}
}
System.out.println("Total legal moves: " + movesStalemate.size());
System.out.println("\n" + "=".repeat(40) + "\n");
}
public static void main(String[] args) {
testChess();
}
}
// Chess Piece class
class Piece {
private char type; // 'P', 'R', 'N', 'B', 'Q', 'K'
private char color; // 'w', 'b'
public Piece(char type, char color) {
this.type = type;
this.color = color;
}
public char getType() { return type; }
public char getColor() { return color; }
@Override
public String toString() {
return color == 'w' ? String.valueOf(type) : String.valueOf(Character.toLowerCase(type));
}
}
// Chess Move class
class Move {
private int startRow, startCol, endRow, endCol;
private Piece promotionPiece; // for pawn promotion
public Move(int startRow, int startCol, int endRow, int endCol) {
this(startRow, startCol, endRow, endCol, null);
}
public Move(int startRow, int startCol, int endRow, int endCol, Piece promotionPiece) {
this.startRow = startRow;
this.startCol = startCol;
this.endRow = endRow;
this.endCol = endCol;
this.promotionPiece = promotionPiece;
}
public int getStartRow() { return startRow; }
public int getStartCol() { return startCol; }
public int getEndRow() { return endRow; }
public int getEndCol() { return endCol; }
public Piece getPromotionPiece() { return promotionPiece; }
// Convert (row, col) 1-based position to algebraic notation
public static String algebraic(int row, int col) {
char file = (char)('a' + (col - 1));
char rank = (char)('8' - (row - 1));
return "" + file + rank;
}
@Override
public String toString() {
String result = algebraic(startRow, startCol) + algebraic(endRow, endCol);
if (promotionPiece != null && promotionPiece.getType() == 'P' && (endRow == 1 || endRow == 8)) {
result += "=" + promotionPiece.getType();
}
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null || getClass() != obj.getClass()) return false;
Move move = (Move) obj;
return startRow == move.startRow && startCol == move.startCol &&
endRow == move.endRow && endCol == move.endCol &&
Objects.equals(promotionPiece, move.promotionPiece);
}
@Override
public int hashCode() {
return Objects.hash(startRow, startCol, endRow, endCol, promotionPiece);
}
}
// Chess Board class
class Board {
private Piece[][] squares;
private char turn; // 'w' or 'b'
private String castlingRights; // "KQkq"
private int[] enPassant; // [row, col] or [0, 0] if none
private int halfMoveClock;
private int fullMoveClock;
public Board(Piece[][] squares, char turn, String castlingRights, int[] enPassant, int halfMoveClock, int fullMoveClock) {
this.squares = new Piece[8][8];
for (int i = 0; i < 8; i++) {
System.arraycopy(squares[i], 0, this.squares[i], 0, 8);
}
this.turn = turn;
this.castlingRights = castlingRights;
this.enPassant = Arrays.copyOf(enPassant, 2);
this.halfMoveClock = halfMoveClock;
this.fullMoveClock = fullMoveClock;
}
public Piece getPieceAt(int row, int col) {
return squares[row - 1][col - 1]; // Convert to 0-based indexing
}
public char getTurn() { return turn; }
public String getCastlingRights() { return castlingRights; }
public int[] getEnPassant() { return enPassant; }
// Convert algebraic notation to (row, col) tuple
public static int[] algebraicToTuple(String alg) {
if (alg.length() != 2 || alg.equals("-")) return new int[]{0, 0};
char file = alg.charAt(0);
char rank = alg.charAt(1);
int col = file - 'a' + 1;
int row = '8' - rank + 1;
return new int[]{row, col};
}
// Parse FEN string
public static Board parseFEN(String fen) {
String[] parts = fen.split(" ");
String boardStr = parts[0];
char turnChar = parts[1].charAt(0);
String castlingRights = parts[2];
int[] enPassant = algebraicToTuple(parts[3]);
int halfMove = Integer.parseInt(parts[4]);
int fullMove = Integer.parseInt(parts[5]);
Piece[][] squares = new Piece[8][8];
int row = 0, col = 0;
for (char c : boardStr.toCharArray()) {
if (c == '/') {
row++;
col = 0;
} else if (Character.isDigit(c)) {
int numEmpty = Character.getNumericValue(c);
for (int i = 0; i < numEmpty; i++) {
squares[row][col] = null;
col++;
}
} else {
char color = Character.isUpperCase(c) ? 'w' : 'b';
char pieceType = Character.toUpperCase(c);
squares[row][col] = new Piece(pieceType, color);
col++;
}
}
return new Board(squares, turnChar, castlingRights, enPassant, halfMove, fullMove);
}
// Print board
public void print() {
System.out.println(" a b c d e f g h");
System.out.println(" +-----------------+");
for (int r = 0; r < 8; r++) {
System.out.print((8 - r) + "|");
for (int c = 0; c < 8; c++) {
Piece piece = squares[r][c];
if (piece == null) {
System.out.print(" .");
} else {
System.out.print(" " + piece);
}
}
System.out.println(" |" + (8 - r));
}
System.out.println(" +-----------------+");
System.out.println(" a b c d e f g h");
System.out.println("Current turn: " + (turn == 'w' ? "White" : "Black"));
System.out.println("Castling rights: " + castlingRights);
}
// Check if square is valid
public static boolean isValidSquare(int row, int col) {
return row >= 1 && row <= 8 && col >= 1 && col <= 8;
}
// Apply move and return new board
public Board makeMove(Move move) {
Piece[][] newSquares = new Piece[8][8];
for (int i = 0; i < 8; i++) {
System.arraycopy(squares[i], 0, newSquares[i], 0, 8);
}
Piece movingPiece = getPieceAt(move.getStartRow(), move.getStartCol());
if (movingPiece == null) return this;
// Handle castling
if (movingPiece.getType() == 'K' && Math.abs(move.getStartCol() - move.getEndCol()) == 2) {
int kingRow = move.getStartRow();
if (move.getEndCol() == 7) { // kingside castling
newSquares[kingRow - 1][6] = movingPiece;
newSquares[kingRow - 1][move.getStartCol() - 1] = null;
Piece rook = getPieceAt(kingRow, 8);
newSquares[kingRow - 1][5] = rook;
newSquares[kingRow - 1][7] = null;
} else if (move.getEndCol() == 3) { // queenside castling
newSquares[kingRow - 1][2] = movingPiece;
newSquares[kingRow - 1][move.getStartCol() - 1] = null;
Piece rook = getPieceAt(kingRow, 1);
newSquares[kingRow - 1][3] = rook;
newSquares[kingRow - 1][0] = null;
}
} else if (movingPiece.getType() == 'P') {
// Handle en passant
if (move.getEndCol() != move.getStartCol() && getPieceAt(move.getEndRow(), move.getEndCol()) == null) {
int targetRow = move.getEndRow() + (movingPiece.getColor() == 'w' ? 1 : -1);
Piece capturedPiece = getPieceAt(targetRow, move.getEndCol());
if (capturedPiece != null && capturedPiece.getType() == 'P' &&
capturedPiece.getColor() != movingPiece.getColor()) {
newSquares[targetRow - 1][move.getEndCol() - 1] = null;
newSquares[move.getEndRow() - 1][move.getEndCol() - 1] = movingPiece;
newSquares[move.getStartRow() - 1][move.getStartCol() - 1] = null;
}
} else {
// Regular pawn move
newSquares[move.getEndRow() - 1][move.getEndCol() - 1] = movingPiece;
newSquares[move.getStartRow() - 1][move.getStartCol() - 1] = null;
}
} else {
// Handle all other moves
newSquares[move.getEndRow() - 1][move.getEndCol() - 1] = movingPiece;
newSquares[move.getStartRow() - 1][move.getStartCol() - 1] = null;
}
// Update castling rights
String newCastlingRights = castlingRights;
if (movingPiece.getType() == 'K') {
if (movingPiece.getColor() == 'w') {
newCastlingRights = newCastlingRights.replace("K", "").replace("Q", "");
} else {
newCastlingRights = newCastlingRights.replace("k", "").replace("q", "");
}
} else if (movingPiece.getType() == 'R') {
if (movingPiece.getColor() == 'w') {
if (move.getStartRow() == 8 && move.getStartCol() == 8) {
newCastlingRights = newCastlingRights.replace("K", "");
} else if (move.getStartRow() == 8 && move.getStartCol() == 1) {
newCastlingRights = newCastlingRights.replace("Q", "");
}
} else {
if (move.getStartRow() == 1 && move.getStartCol() == 8) {
newCastlingRights = newCastlingRights.replace("k", "");
} else if (move.getStartRow() == 1 && move.getStartCol() == 1) {
newCastlingRights = newCastlingRights.replace("q", "");
}
}
}
if (newCastlingRights.isEmpty()) {
newCastlingRights = "-";
}
// Handle en passant
int[] newEnPassant = {0, 0};
if (movingPiece.getType() == 'P' && Math.abs(move.getStartRow() - move.getEndRow()) == 2) {
newEnPassant[0] = move.getEndRow() + (movingPiece.getColor() == 'w' ? 1 : -1);
newEnPassant[1] = move.getEndCol();
}
char newTurn = (turn == 'w' ? 'b' : 'w');
return new Board(newSquares, newTurn, newCastlingRights, newEnPassant,
halfMoveClock + 1, fullMoveClock + (newTurn == 'b' ? 1 : 0));
}
// Find king position
public int[] findKing(char kingColor) {
for (int r = 1; r <= 8; r++) {
for (int c = 1; c <= 8; c++) {
Piece piece = getPieceAt(r, c);
if (piece != null && piece.getType() == 'K' && piece.getColor() == kingColor) {
return new int[]{r, c};
}
}
}
return null;
}
// Check if square is attacked
public boolean isSquareAttacked(int row, int col, char attackingColor) {
// Check pawn attacks
int pawnDir = (attackingColor == 'w' ? -1 : 1);
for (int dc : new int[]{-1, 1}) {
int targetRow = row + pawnDir;
int targetCol = col + dc;
if (isValidSquare(targetRow, targetCol)) {
Piece piece = getPieceAt(targetRow, targetCol);
if (piece != null && piece.getColor() == attackingColor && piece.getType() == 'P') {
return true;
}
}
}
// Check knight attacks
int[][] knightMoves = {{-2, -1}, {-2, 1}, {-1, -2}, {-1, 2}, {1, -2}, {1, 2}, {2, -1}, {2, 1}};
for (int[] move : knightMoves) {
int targetRow = row + move[0];
int targetCol = col + move[1];
if (isValidSquare(targetRow, targetCol)) {
Piece piece = getPieceAt(targetRow, targetCol);
if (piece != null && piece.getColor() == attackingColor && piece.getType() == 'N') {
return true;
}
}
}
// Check straight line attacks (rook, queen)
int[][] straightDirs = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
for (int[] dir : straightDirs) {
for (int i = 1; i <= 7; i++) {
int targetRow = row + i * dir[0];
int targetCol = col + i * dir[1];
if (!isValidSquare(targetRow, targetCol)) break;
Piece piece = getPieceAt(targetRow, targetCol);
if (piece != null) {
if (piece.getColor() == attackingColor &&
(piece.getType() == 'R' || piece.getType() == 'Q')) {
return true;
} else {
break;
}
}
}
}
// Check diagonal attacks (bishop, queen)
int[][] diagonalDirs = {{1, 1}, {1, -1}, {-1, 1}, {-1, -1}};
for (int[] dir : diagonalDirs) {
for (int i = 1; i <= 7; i++) {
int targetRow = row + i * dir[0];
int targetCol = col + i * dir[1];
if (!isValidSquare(targetRow, targetCol)) break;
Piece piece = getPieceAt(targetRow, targetCol);
if (piece != null) {
if (piece.getColor() == attackingColor &&
(piece.getType() == 'B' || piece.getType() == 'Q')) {
return true;
} else {
break;
}
}
}
}
// Check king attacks
int[][] kingMoves = {{-1, -1}, {-1, 0}, {-1, 1}, {0, -1}, {0, 1}, {1, -1}, {1, 0}, {1, 1}};
for (int[] move : kingMoves) {
int targetRow = row + move[0];
int targetCol = col + move[1];
if (isValidSquare(targetRow, targetCol)) {
Piece piece = getPieceAt(targetRow, targetCol);
if (piece != null && piece.getColor() == attackingColor && piece.getType() == 'K') {
return true;
}
}
}
return false;
}
// Check if king is in check
public boolean inCheck(char color) {
int[] kingPos = findKing(color);
if (kingPos == null) {
System.out.println("Warning: King of color " + color + " not found on board.");
return false;
}
char attackingColor = (color == 'w' ? 'b' : 'w');
return isSquareAttacked(kingPos[0], kingPos[1], attackingColor);
}
// Get legal moves
public List<Move> getLegalMoves() {
List<Move> allMoves = new ArrayList<>();
char movingPlayerColor = turn;
for (int r = 1; r <= 8; r++) {
for (int c = 1; c <= 8; c++) {
Piece piece = getPieceAt(r, c);
if (piece != null && piece.getColor() == movingPlayerColor) {
switch (piece.getType()) {
case 'P': allMoves.addAll(getPawnMoves(r, c, piece)); break;
case 'R': allMoves.addAll(getRookMoves(r, c, piece)); break;
case 'N': allMoves.addAll(getKnightMoves(r, c, piece)); break;
case 'B': allMoves.addAll(getBishopMoves(r, c, piece)); break;
case 'Q': allMoves.addAll(getQueenMoves(r, c, piece)); break;
case 'K': allMoves.addAll(getKingMoves(r, c, piece)); break;
}
}
}
}
// Filter out moves that leave king in check
List<Move> legalMoves = new ArrayList<>();
for (Move move : allMoves) {
Board tempBoard = makeMove(move);
if (!tempBoard.inCheck(movingPlayerColor)) {
legalMoves.add(move);
}
}
return legalMoves;
}
// Get pawn moves
private List<Move> getPawnMoves(int r, int c, Piece piece) {
List<Move> moves = new ArrayList<>();
int direction = (piece.getColor() == 'w' ? -1 : 1);
int startRank = (piece.getColor() == 'w' ? 7 : 2);
// Forward move
int targetRow = r + direction;
if (isValidSquare(targetRow, c) && getPieceAt(targetRow, c) == null) {
if (targetRow == 1 || targetRow == 8) { // Promotion
for (char promotionType : new char[]{'Q', 'R', 'B', 'N'}) {
moves.add(new Move(r, c, targetRow, c, new Piece(promotionType, piece.getColor())));
}
} else {
moves.add(new Move(r, c, targetRow, c));
// Double move from starting position
if (r == startRank) {
int doubleTargetRow = r + 2 * direction;
if (isValidSquare(doubleTargetRow, c) && getPieceAt(doubleTargetRow, c) == null) {
moves.add(new Move(r, c, doubleTargetRow, c));
}
}
}
}
// Capture moves
for (int dc : new int[]{-1, 1}) {
targetRow = r + direction;
int targetCol = c + dc;
if (isValidSquare(targetRow, targetCol)) {
Piece targetPiece = getPieceAt(targetRow, targetCol);
if ((targetPiece != null && targetPiece.getColor() != piece.getColor()) ||
(enPassant[0] == targetRow && enPassant[1] == targetCol)) {
moves.add(new Move(r, c, targetRow, targetCol));
}
}
}
return moves;
}
// Get sliding moves (for rook, bishop, queen)
private List<Move> getSlidingMoves(int r, int c, Piece piece, int[][] directions) {
List<Move> moves = new ArrayList<>();
for (int[] dir : directions) {
for (int i = 1; i <= 7; i++) {
int targetRow = r + i * dir[0];
int targetCol = c + i * dir[1];
if (!isValidSquare(targetRow, targetCol)) break;
Piece targetPiece = getPieceAt(targetRow, targetCol);
if (targetPiece == null) {
moves.add(new Move(r, c, targetRow, targetCol));
} else if (targetPiece.getColor() != piece.getColor()) {
moves.add(new Move(r, c, targetRow, targetCol));
break;
} else {
break;
}
}
}
return moves;
}
private List<Move> getRookMoves(int r, int c, Piece piece) {
int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
return getSlidingMoves(r, c, piece, directions);
}
private List<Move> getBishopMoves(int r, int c, Piece piece) {
int[][] directions = {{1, 1}, {1, -1}, {-1, 1}, {-1, -1}};
return getSlidingMoves(r, c, piece, directions);
}
private List<Move> getQueenMoves(int r, int c, Piece piece) {
int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1}};
return getSlidingMoves(r, c, piece, directions);
}
private List<Move> getKnightMoves(int r, int c, Piece piece) {
List<Move> moves = new ArrayList<>();
int[][] knightOffsets = {{-2, -1}, {-2, 1}, {-1, -2}, {-1, 2}, {1, -2}, {1, 2}, {2, -1}, {2, 1}};
for (int[] offset : knightOffsets) {
int targetRow = r + offset[0];
int targetCol = c + offset[1];
if (isValidSquare(targetRow, targetCol)) {
Piece targetPiece = getPieceAt(targetRow, targetCol);
if (targetPiece == null || targetPiece.getColor() != piece.getColor()) {
moves.add(new Move(r, c, targetRow, targetCol));
}
}
}
return moves;
}
private List<Move> getKingMoves(int r, int c, Piece piece) {
List<Move> moves = new ArrayList<>();
int[][] kingOffsets = {{-1, -1}, {-1, 0}, {-1, 1}, {0, -1}, {0, 1}, {1, -1}, {1, 0}, {1, 1}};
for (int[] offset : kingOffsets) {
int targetRow = r + offset[0];
int targetCol = c + offset[1];
if (isValidSquare(targetRow, targetCol)) {
Piece targetPiece = getPieceAt(targetRow, targetCol);
if (targetPiece == null || targetPiece.getColor() != piece.getColor()) {
moves.add(new Move(r, c, targetRow, targetCol));
}
}
}
// Castling
char kingColor = piece.getColor();
char opponentColor = (kingColor == 'w' ? 'b' : 'w');
if (inCheck(kingColor)) return moves;
int initialKingRow = (kingColor == 'w' ? 8 : 1);
if (!(r == initialKingRow && c == 5)) return moves;
// Kingside castling
if (kingColor == 'w' && castlingRights.contains("K")) {
if (getPieceAt(initialKingRow, 6) == null && getPieceAt(initialKingRow, 7) == null) {
Piece rook = getPieceAt(initialKingRow, 8);
if (rook != null && rook.getType() == 'R' && rook.getColor() == kingColor) {
if (!isSquareAttacked(initialKingRow, 5, opponentColor) &&
!isSquareAttacked(initialKingRow, 6, opponentColor) &&
!isSquareAttacked(initialKingRow, 7, opponentColor)) {
moves.add(new Move(r, c, initialKingRow, 7));
}
}
}
}
// Queenside castling
if (kingColor == 'w' && castlingRights.contains("Q")) {
if (getPieceAt(initialKingRow, 2) == null && getPieceAt(initialKingRow, 3) == null &&
getPieceAt(initialKingRow, 4) == null) {
Piece rook = getPieceAt(initialKingRow, 1);
if (rook != null && rook.getType() == 'R' && rook.getColor() == kingColor) {
if (!isSquareAttacked(initialKingRow, 5, opponentColor) &&
!isSquareAttacked(initialKingRow, 4, opponentColor) &&
!isSquareAttacked(initialKingRow, 3, opponentColor)) {
moves.add(new Move(r, c, initialKingRow, 3));
}
}
}
}
// Black castling
if (kingColor == 'b' && castlingRights.contains("k")) {
if (getPieceAt(initialKingRow, 6) == null && getPieceAt(initialKingRow, 7) == null) {
Piece rook = getPieceAt(initialKingRow, 8);
if (rook != null && rook.getType() == 'R' && rook.getColor() == kingColor) {
if (!isSquareAttacked(initialKingRow, 5, opponentColor) &&
!isSquareAttacked(initialKingRow, 6, opponentColor) &&
!isSquareAttacked(initialKingRow, 7, opponentColor)) {
moves.add(new Move(r, c, initialKingRow, 7));
}
}
}
}
if (kingColor == 'b' && castlingRights.contains("q")) {
if (getPieceAt(initialKingRow, 2) == null && getPieceAt(initialKingRow, 3) == null &&
getPieceAt(initialKingRow, 4) == null) {
Piece rook = getPieceAt(initialKingRow, 1);
if (rook != null && rook.getType() == 'R' && rook.getColor() == kingColor) {
if (!isSquareAttacked(initialKingRow, 5, opponentColor) &&
!isSquareAttacked(initialKingRow, 4, opponentColor) &&
!isSquareAttacked(initialKingRow, 3, opponentColor)) {
moves.add(new Move(r, c, initialKingRow, 3));
}
}
}
}
return moves;
}
}
- Output:
--- Position with Black in Check --- a b c d e f g h +-----------------+ 8| . . . . k . . . |8 7| . . . . . . . . |7 6| . . . . . . . . |6 5| . . . . . . . Q |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| . . . . . . . . |2 1| . . . . K . . . |1 +-----------------+ a b c d e f g h Current turn: Black Castling rights: - Is Black king in check? true Legal moves for Black (to get out of check or make other moves): --- Starting Position --- a b c d e f g h +-----------------+ 8| r n b q k b n r |8 7| p p p p p p p p |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| P P P P P P P P |2 1| R N B Q K B N R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for Black (to get out of check or make other moves): - e8d8 - e8f8 - e8d7 - e8e7 Total legal moves: 4 ======================================== --- Mid-game Position (White to move) --- a b c d e f g h +-----------------+ 8| r . . . k . . r |8 7| p . p p q p b . |7 6| b n . . p n . p |6 5| . . . P P . p . |5 4| . p . . P . . . |4 3| . . N . . N . . |3 2| P P P B B P P P |2 1| R . . Q K . . R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White: - d5d6 - d5e6 - e5f6 - c3b5 - c3a4 - c3b1 - f3g5 - f3d4 - f3h4 - f3g1 - a2a3 - a2a4 - b2b3 - d2c1 - d2e3 - d2f4 - d2g5 - e2f1 - e2d3 - e2c4 - e2b5 - e2a6 - g2g3 - g2g4 - h2h3 - h2h4 - a1b1 - a1c1 - d1c1 - d1b1 - e1f1 - e1g1 - h1g1 - h1f1 Total legal moves: 34 ======================================== --- Position Allowing White Castling --- a b c d e f g h +-----------------+ 8| r . . . k . . r |8 7| . . . . . . . . |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| . . . . . . . . |2 1| R . . . K . . R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White (including castling): - a1b1 - a1c1 - a1d1 - a1a2 - a1a3 - a1a4 - a1a5 - a1a6 - a1a7 - a1a8 - e1d2 - e1e2 - e1f2 - e1d1 - e1f1 - e1g1 - e1c1 - h1g1 - h1f1 - h1h2 - h1h3 - h1h4 - h1h5 - h1h6 - h1h7 - h1h8 Total legal moves: 26 ======================================== --- Position Allowing Pawn Promotion --- a b c d e f g h +-----------------+ 8| . . . . . . . . |8 7| . . . . P . . k |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| . . . . . . . . |2 1| R . . . K . . R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White (including pawn promotions): - e7e8 - e7e8 - e7e8 - e7e8 - a1b1 - a1c1 - a1d1 - a1a2 - a1a3 - a1a4 - a1a5 - a1a6 - a1a7 - a1a8 - e1d2 - e1e2 - e1f2 - e1d1 - e1f1 - e1g1 - e1c1 - h1g1 - h1f1 - h1h2 - h1h3 - h1h4 - h1h5 - h1h6 - h1h7 Total legal moves: 29 ======================================== --- Position Allowing En Passant --- a b c d e f g h +-----------------+ 8| r n b q k b n r |8 7| p p p . p . p p |7 6| . . . . . . . . |6 5| . . . p P p . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| P P P P . P P P |2 1| R N B Q K B N R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White (including en passant capture): - e5e6 - e5f6 - a2a3 - a2a4 - b2b3 - b2b4 - c2c3 - c2c4 - d2d3 - d2d4 - f2f3 - f2f4 - g2g3 - g2g4 - h2h3 - h2h4 - b1a3 - b1c3 - d1e2 - d1f3 - d1g4 - d1h5 - e1e2 - f1e2 - f1d3 - f1c4 - f1b5 - f1a6 - g1f3 - g1h3 - g1e2 Total legal moves: 31 ======================================== --- Stalemate Position --- a b c d e f g h +-----------------+ 8| . . . . . . . . |8 7| . . . . . . . . |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . k . |3 2| . . . . . b . . |2 1| . . . . . . . K |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: - Legal moves for White (should be none): No legal moves. (This indicates stalemate) Total legal moves: 0 ========================================
A full chess-playing program seems too complex a project for this wiki. The program below does not actually play chess but can take a position given by FEN notation (see Forsyth–Edwards_Notation) and return all legal moves, including en passant, pawn promotion, and castling.
""" Chess moves """
""" Chess Piece struct. type: Char ('P', 'R', 'N', 'B', 'Q', 'K') color: 'w', 'b' """
struct Piece
type::Char
color::Char
end
Base.print(io::IO, p::Piece) = print(io, p.color == 'w' ? p.type : lowercase(p.type))
""" Chess Board is 8 x 8 Matrix """
struct Board
squares::Matrix{Union{Piece, Nothing}}
turn::Char # 'w' or 'b'
castlingrights::String # starts as "KQkq", kingside queenside for white, black
enpassant::Tuple{Int, Int} # position of a pawn that can be captured en passant, (0, 0) if none
halfmoveclock::Int # for fifty-move rule
fullmoveclock::Int # running total of full moves
end
""" Chess Move struct, 1-based, defined by the movement not the Piece moved """
struct Move
start_row::Int
start_col::Int
end_row::Int
end_col::Int
piece::Union{Piece, Nothing} # for pawn promotion
function Move(start_row::Int, start_col::Int, end_row::Int, end_col::Int, piece::Union{Piece, Nothing} = nothing)
new(start_row, start_col, end_row, end_col, piece)
end
end
""" Convert (row, col) 1-based position to algebraic notation (e.g., "a1") """
function algebraic(row::Int, col::Int, piece::Union{Piece, Nothing} = nothing)::String
file = Char('a' + (col - 1)) # columns are 1 to 8, map to 'a' to 'h'
rank = Char('8' - (row - 1)) # rows are 1 to 8, map to '8' to '1'
# Handle pawn promotion
if piece !== nothing && piece.type == 'P' && (row == 1 || row == 8)
return string(file, rank, "=", piece.type)
end
return string(file, rank)
end
""" Convert a Move to algebraic notation (e.g., "e2e4") """
function Base.print(io::IO, m::Move)
print(io, "$(algebraic(m.start_row, m.start_col, m.piece))$(algebraic(m.end_row, m.end_col, m.piece))")
end
""" Convert algebraic notation to a Tuple{Int, Int}. """
function algebraic2tuple(alg::AbstractString)::Tuple{Int, Int}
length(alg) != 2 && return (0, 0) # "-" or invalid input
file = alg[1]
rank = alg[2]
col = Int(file - 'a') + 1 # 'a' maps to 1, 'h' to 8
row = Int('8' - rank) + 1 # '8' maps to 1, '1' to 8
return (row, col)
end
""" Parses a FEN string. Returns a Board set per FEN """
function parseFEN(fen_string::String)::Board
parts = split(fen_string, ' ')
boardstr = parts[1]
turnchar = parts[2][1]
castlingrights = parts[3]
enpassant = algebraic2tuple(parts[4])
halfmove = parse(Int, parts[5])
fullmove = parse(Int, parts[6])
squares = Matrix{Union{Piece, Nothing}}(undef, 8, 8)
row, col = 1, 1
for char in boardstr
if char == '/'
row += 1
col = 1
elseif isdigit(char)
num_empty = parse(Int, char)
for _ in 1:num_empty
squares[row, col] = nothing
col += 1
end
else
color = isuppercase(char) ? 'w' : 'b'
piece_type = uppercase(char)
squares[row, col] = Piece(piece_type, color)
col += 1
end
end
return Board(squares, turnchar, castlingrights, enpassant, halfmove, fullmove)
end
""" Prints an ASCII visual representation of the chess board to stdout """
function Base.print(io::IO, board::Board)
println(io, " a b c d e f g h")
println(io, " +-----------------+")
for r in 1:8
print(io, "$(9 - r)|")
for c in 1:8
piece = board.squares[r, c]
if piece === nothing
print(io, " .")
else
print(io, " $piece")
end
end
println(io, " |$(9 - r)")
end
println(io, " +-----------------+")
println(io, " a b c d e f g h")
println(io, "Current turn: $(board.turn == 'w' ? "White" : "Black")")
println(io, "Castling rights: $(board.castlingrights)")
end
""" Checks if the given row and column are within the 8x8 board boundaries (1-indexed). """
@inline isvalidsquare(row::Int, col::Int)::Bool = 1 <= row <= 8 && 1 <= col <= 8
""" Returns the piece at the 1-based (row, col) on the board, or nothing if empty. """
piece_at(brd::Board, row, col)::Union{Piece, Nothing} = brd.squares[row, col]
""" Applies a move to a new (cloned) board state and returns the new Board. """
function move!(board::Board, move::Move)::Board
new_squares = deepcopy(board.squares)
moving_piece = piece_at(board, move.start_row, move.start_col)
moving_piece === nothing && return board # sanity check
# Handle castling
if moving_piece.type == 'K' && abs(move.start_col - move.end_col) == 2
king_row = move.start_row
if move.end_col == 7 # kingside castling
new_squares[king_row, 7] = moving_piece
new_squares[king_row, move.start_col] = nothing
rook = piece_at(board, king_row, 8)
new_squares[king_row, 6] = rook
new_squares[king_row, 8] = nothing
elseif move.end_col == 3 # queenside castling
new_squares[king_row, 3] = moving_piece
new_squares[king_row, move.start_col] = nothing
rook = piece_at(board, king_row, 1)
new_squares[king_row, 4] = rook
new_squares[king_row, 1] = nothing
end
elseif moving_piece.type == 'P' # handle special en passant pawn moves
if move.end_col != move.start_col && piece_at(board, move.end_row, move.end_col) isa Nothing
target_row = move.end_row + (moving_piece.color == 'w' ? 1 : -1)
captured_piece = piece_at(board, target_row, move.end_col)
if captured_piece !== nothing && captured_piece.type == 'P' && captured_piece.color != moving_piece.color
new_squares[target_row, move.end_col] = nothing
new_squares[move.end_row, move.end_col] = moving_piece
new_squares[move.start_row, move.start_col] = nothing
end
end
else
# Handle all other moves
new_squares[move.end_row, move.end_col] = moving_piece
new_squares[move.start_row, move.start_col] = nothing
end
# Update castling rights
new_castling_rights = board.castlingrights
if moving_piece.type == 'K'
if moving_piece.color == 'w'
new_castling_rights = replace(new_castling_rights, 'K' => "", 'Q' => "")
else
new_castling_rights = replace(new_castling_rights, 'k' => "", 'q' => "")
end
elseif moving_piece.type == 'R'
if moving_piece.color == 'w'
if move.start_row == 8 && move.start_col == 8
new_castling_rights = replace(new_castling_rights, 'K' => "")
elseif move.start_row == 8 && move.start_col == 1
new_castling_rights = replace(new_castling_rights, 'Q' => "")
end
else
if move.start_row == 1 && move.start_col == 8
new_castling_rights = replace(new_castling_rights, 'k' => "")
elseif move.start_row == 1 && move.start_col == 1
new_castling_rights = replace(new_castling_rights, 'q' => "")
end
end
end
captured_piece_at_dest = piece_at(board, move.end_row, move.end_col)
if captured_piece_at_dest !== nothing && captured_piece_at_dest.type == 'R'
if captured_piece_at_dest.color == 'w'
if move.end_row == 8 && move.end_col == 8
new_castling_rights = replace(new_castling_rights, 'K' => "")
elseif move.end_row == 8 && move.end_col == 1
new_castling_rights = replace(new_castling_rights, 'Q' => "")
end
else
if move.end_row == 1 && move.end_col == 8
new_castling_rights = replace(new_castling_rights, 'k' => "")
elseif move.end_row == 1 && move.end_col == 1
new_castling_rights = replace(new_castling_rights, 'q' => "")
end
end
end
if isempty(new_castling_rights)
new_castling_rights = "-"
end
# Handle en passant
new_enpassant = (0, 0)
if moving_piece.type == 'P' && abs(move.start_row - move.end_row) == 2
new_enpassant = (move.end_row + (moving_piece.color == 'w' ? 1 : -1), move.end_col)
else
new_enpassant = board.enpassant
end
new_turn = (board.turn == 'w' ? 'b' : 'w')
return Board(new_squares, new_turn, new_castling_rights, new_enpassant,
board.halfmoveclock + 1, board.fullmoveclock + (new_turn == 'b' ? 1 : 0))
end
""" Finds the 1-based (row, col) of the king of the specified color on the board. """
function findking(board::Board, king_color::Char)::Union{Tuple{Int, Int}, Nothing}
for r in 1:8
for c in 1:8
piece = piece_at(board, r, c)
if piece !== nothing && piece.type == 'K' && piece.color == king_color
return (r, c)
end
end
end
return nothing
end
""" Checks if a given square (row, col) is attacked by any piece of attacking_color """
function issquareattacked(board::Board, row::Int, col::Int, attacking_color::Char)::Bool
opponent_color = attacking_color
pawn_dir = (opponent_color == 'w' ? -1 : 1)
for dc in [-1, 1]
target_row, target_col = row + pawn_dir, col + dc
if isvalidsquare(target_row, target_col)
piece = piece_at(board, target_row, target_col)
if piece !== nothing && piece.color == opponent_color && piece.type == 'P'
return true
end
end
end
knight_moves = [(-2, -1), (-2, 1), (-1, -2), (-1, 2), (1, -2), (1, 2), (2, -1), (2, 1)]
for (dr, dc) in knight_moves
target_row, target_col = row + dr, col + dc
if isvalidsquare(target_row, target_col)
piece = piece_at(board, target_row, target_col)
if piece !== nothing && piece.color == opponent_color && piece.type == 'N'
return true
end
end
end
straight_dirs = [(0, 1), (0, -1), (1, 0), (-1, 0)]
for (dr, dc) in straight_dirs
for i in 1:7
target_row, target_col = row + i * dr, col + i * dc
if !isvalidsquare(target_row, target_col)
break
end
piece = piece_at(board, target_row, target_col)
if piece !== nothing
if piece.color == opponent_color && (piece.type == 'R' || piece.type == 'Q')
return true
else
break
end
end
end
end
diagonal_dirs = [(1, 1), (1, -1), (-1, 1), (-1, -1)]
for (dr, dc) in diagonal_dirs
for i in 1:7
target_row, target_col = row + i * dr, col + i * dc
if !isvalidsquare(target_row, target_col)
break
end
piece = piece_at(board, target_row, target_col)
if piece !== nothing
if piece.color == opponent_color && (piece.type == 'B' || piece.type == 'Q')
return true
else
break
end
end
end
end
king_moves = [(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1)]
for (dr, dc) in king_moves
target_row, target_col = row + dr, col + dc
if isvalidsquare(target_row, target_col)
piece = piece_at(board, target_row, target_col)
if piece !== nothing && piece.color == opponent_color && piece.type == 'K'
return true
end
end
end
return false
end
""" True if the color king is currently in check on the given board. """
function incheck(board::Board, color::Char)::Bool
king_pos = findking(board, color)
if king_pos === nothing
println("Warning: King of color $color not found on board.")
return false
end
king_row, king_col = king_pos
attacking_color = (color == 'w' ? 'b' : 'w')
return issquareattacked(board, king_row, king_col, attacking_color)
end
""" Get legal moves for a pawn at (r, c). """
function pawnmoves(board::Board, r::Int, c::Int, piece::Piece)::Vector{Move}
moves = Move[]
direction = (piece.color == 'w' ? -1 : 1)
start_rank = (piece.color == 'w' ? 7 : 2)
target_row = r + direction
if isvalidsquare(target_row, c) && piece_at(board, target_row, c) === nothing
if target_row == 1 || target_row == 8 # Promotion row
for promotion_piece in ['Q', 'R', 'B', 'N']
push!(moves, Move(r, c, target_row, c, Piece(promotion_piece, piece.color)))
end
else
push!(moves, Move(r, c, target_row, c))
if r == start_rank
double_target_row = r + 2 * direction
if isvalidsquare(double_target_row, c) && piece_at(board, double_target_row, c) === nothing
push!(moves, Move(r, c, double_target_row, c))
end
end
end
end
for dc in [-1, 1]
target_row, target_col = r + direction, c + dc
if isvalidsquare(target_row, target_col)
target_piece = piece_at(board, target_row, target_col)
if target_piece !== nothing && target_piece.color != piece.color ||
board.enpassant == (target_row, target_col)
push!(moves, Move(r, c, target_row, target_col))
end
end
end
return moves
end
""" Helper for Rook, Bishop, Queen, get moves in sliding order along given directions """
function getslidingmoves(board::Board, r::Int, c::Int, piece::Piece, directions::Vector{Tuple{Int, Int}})::Vector{Move}
moves = Move[]
for (dr, dc) in directions
for i in 1:7
target_row, target_col = r + i * dr, c + i * dc
if !isvalidsquare(target_row, target_col)
break
end
target_piece = piece_at(board, target_row, target_col)
if target_piece === nothing
push!(moves, Move(r, c, target_row, target_col))
elseif target_piece.color != piece.color
push!(moves, Move(r, c, target_row, target_col))
break
else
break
end
end
end
return moves
end
""" Generate moves for a rook at (r, c). """
function rookmoves(board::Board, r::Int, c::Int, piece::Piece)::Vector{Move}
directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
return getslidingmoves(board, r, c, piece, directions)
end
""" Generate moves for a bishop at (r, c). """
function bishopmoves(board::Board, r::Int, c::Int, piece::Piece)::Vector{Move}
directions = [(1, 1), (1, -1), (-1, 1), (-1, -1)]
return getslidingmoves(board, r, c, piece, directions)
end
""" Generate moves for a queen at (r, c). """
function queenmoves(board::Board, r::Int, c::Int, piece::Piece)::Vector{Move}
directions = [(0, 1), (0, -1), (1, 0), (-1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
return getslidingmoves(board, r, c, piece, directions)
end
""" Generate moves for a knight at (r, c). """
function knightmoves(board::Board, r::Int, c::Int, piece::Piece)::Vector{Move}
moves = Move[]
knight_offsets = [(-2, -1), (-2, 1), (-1, -2), (-1, 2), (1, -2), (1, 2), (2, -1), (2, 1)]
for (dr, dc) in knight_offsets
target_row, target_col = r + dr, c + dc
if isvalidsquare(target_row, target_col)
target_piece = piece_at(board, target_row, target_col)
if target_piece === nothing || target_piece.color != piece.color
push!(moves, Move(r, c, target_row, target_col))
end
end
end
return moves
end
""" Generate moves for a king at (r, c) """
function kingmoves(board::Board, r::Int, c::Int, piece::Piece)::Vector{Move}
moves = Move[]
king_offsets = [(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1)]
for (dr, dc) in king_offsets
target_row, target_col = r + dr, c + dc
if isvalidsquare(target_row, target_col)
target_piece = piece_at(board, target_row, target_col)
if target_piece === nothing || target_piece.color != piece.color
push!(moves, Move(r, c, target_row, target_col))
end
end
end
king_color = piece.color
opponent_color = (king_color == 'w' ? 'b' : 'w')
if incheck(board, king_color)
return moves
end
initial_king_row = (king_color == 'w' ? 8 : 1)
if !(r == initial_king_row && c == 5)
return moves
end
if king_color == 'w' && 'K' in board.castlingrights
if piece_at(board, initial_king_row, 6) === nothing && piece_at(board, initial_king_row, 7) === nothing
rook = piece_at(board, initial_king_row, 8)
if rook !== nothing && rook.type == 'R' && rook.color == king_color
if !issquareattacked(board, initial_king_row, 5, opponent_color) &&
!issquareattacked(board, initial_king_row, 6, opponent_color) &&
!issquareattacked(board, initial_king_row, 7, opponent_color)
push!(moves, Move(r, c, initial_king_row, 7))
end
end
end
end
if king_color == 'w' && 'Q' in board.castlingrights
if piece_at(board, initial_king_row, 2) === nothing && piece_at(board, initial_king_row, 3) === nothing &&
piece_at(board, initial_king_row, 4) === nothing
rook = piece_at(board, initial_king_row, 1)
if rook !== nothing && rook.type == 'R' && rook.color == king_color
if !issquareattacked(board, initial_king_row, 5, opponent_color) &&
!issquareattacked(board, initial_king_row, 4, opponent_color) &&
!issquareattacked(board, initial_king_row, 3, opponent_color)
push!(moves, Move(r, c, initial_king_row, 3))
end
end
end
end
if king_color == 'b' && 'k' in board.castlingrights
if piece_at(board, initial_king_row, 6) === nothing && piece_at(board, initial_king_row, 7) === nothing
rook = piece_at(board, initial_king_row, 8)
if rook !== nothing && rook.type == 'R' && rook.color == king_color
if !issquareattacked(board, initial_king_row, 5, opponent_color) &&
!issquareattacked(board, initial_king_row, 6, opponent_color) &&
!issquareattacked(board, initial_king_row, 7, opponent_color)
push!(moves, Move(r, c, initial_king_row, 7))
end
end
end
end
if king_color == 'b' && 'q' in board.castlingrights
if piece_at(board, initial_king_row, 2) === nothing && piece_at(board, initial_king_row, 3) === nothing &&
piece_at(board, initial_king_row, 4) === nothing
rook = piece_at(board, initial_king_row, 1)
if rook !== nothing && rook.type == 'R' && rook.color == king_color
if !issquareattacked(board, initial_king_row, 5, opponent_color) &&
!issquareattacked(board, initial_king_row, 4, opponent_color) &&
!issquareattacked(board, initial_king_row, 3, opponent_color)
push!(moves, Move(r, c, initial_king_row, 3))
end
end
end
end
return moves
end
""" Gets all legal moves for the current player on the given board. """
function getlegalmoves(board::Board)::Vector{Move}
allmoves = Move[]
movingplayercolor = board.turn
for r in 1:8
for c in 1:8
piece = piece_at(board, r, c)
if piece !== nothing && piece.color == movingplayercolor
if piece.type == 'P'
append!(allmoves, pawnmoves(board, r, c, piece))
elseif piece.type == 'R'
append!(allmoves, rookmoves(board, r, c, piece))
elseif piece.type == 'N'
append!(allmoves, knightmoves(board, r, c, piece))
elseif piece.type == 'B'
append!(allmoves, bishopmoves(board, r, c, piece))
elseif piece.type == 'Q'
append!(allmoves, queenmoves(board, r, c, piece))
elseif piece.type == 'K'
append!(allmoves, kingmoves(board, r, c, piece))
end
end
end
end
legal_moves = Move[]
for mov in unique(allmoves)
temp_board = move!(board, mov)
if !incheck(temp_board, movingplayercolor)
push!(legal_moves, mov)
end
end
return legal_moves
end
""" Test various chess positions and legal moves """
function testchess()
fen_start = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
board_start = parseFEN(fen_start)
println("--- Starting Position ---")
print(board_start)
moves_start = getlegalmoves(board_start)
println("\nLegal moves for White:")
if isempty(moves_start)
println("No legal moves.")
else
for mov in moves_start
println("- $mov")
end
end
println("Total legal moves: $(length(moves_start))")
println("\n" * "="^40 * "\n")
fen_check = "4k3/8/8/7Q/8/8/8/4K3 b - - 0 1"
board_check = parseFEN(fen_check)
println("--- Position with Black in Check ---")
print(board_check)
println("\nIs Black king in check? $(incheck(board_check, 'b'))")
moves_check = getlegalmoves(board_check)
println("\nLegal moves for Black (to get out of check or make other moves):")
if isempty(moves_check)
println("No legal moves. (This might indicate checkmate or stalemate)")
else
for mov in moves_check
println("- $mov")
end
end
println("Total legal moves: $(length(moves_check))")
println("\n" * "="^40 * "\n")
fen_midgame = "r3k2r/p1ppqpb1/bn2pn1p/3PP1p1/1p2P3/2N2N2/PPPBBPPP/R2QK2R w KQkq - 0 1"
board_midgame = parseFEN(fen_midgame)
println("--- Mid-game Position (White to move) ---")
print(board_midgame)
moves_midgame = getlegalmoves(board_midgame)
println("\nLegal moves for White:")
if isempty(moves_midgame)
println("No legal moves.")
else
for mov in moves_midgame
println("- $mov")
end
end
println("Total legal moves: $(length(moves_midgame))")
println("\n" * "="^40 * "\n")
fen_castling_white = "r3k2r/8/8/8/8/8/8/R3K2R w KQkq - 0 1"
board_castling_white = parseFEN(fen_castling_white)
println("--- Position Allowing White Castling ---")
print(board_castling_white)
moves_castling_white = getlegalmoves(board_castling_white)
println("\nLegal moves for White (including castling):")
if isempty(moves_castling_white)
println("No legal moves.")
else
for mov in moves_castling_white
println("- $mov")
end
end
println("Total legal moves: $(length(moves_castling_white))")
println("\n" * "="^40 * "\n")
fen_promotion = "8/4P2k/8/8/8/8/8/R3K2R w KQkq - 0 1"
board_promotion = parseFEN(fen_promotion)
println("--- Position Allowing Pawn Promotion ---")
print(board_promotion)
moves_promotion = getlegalmoves(board_promotion)
println("\nLegal moves for White (including pawn promotions):")
if isempty(moves_promotion)
println("No legal moves.")
else
for mov in moves_promotion
println("- $mov")
end
end
println("Total legal moves: $(length(moves_promotion))")
println("\n" * "="^40 * "\n")
fen_enpassant = "rnbqkbnr/ppp1p1pp/8/3pPp2/8/8/PPPP1PPP/RNBQKBNR w KQkq f6 0 3"
board_enpassant = parseFEN(fen_enpassant)
println("--- Position Allowing En Passant ---")
print(board_enpassant)
moves_including_enpassant = getlegalmoves(board_enpassant)
println("\nLegal moves for White (including en passant capture):")
if isempty(moves_including_enpassant)
println("No legal moves.")
else
for mov in moves_including_enpassant
println("- $mov")
end
end
println("Total legal moves: $(length(moves_including_enpassant))")
println("\n" * "="^40 * "\n")
fen_stalemate = "8/8/8/8/8/6k1/5b2/7K w - - 12 95"
board_stalemate = parseFEN(fen_stalemate)
println("--- Stalemate Position ---")
print(board_stalemate)
moves_stalemate = getlegalmoves(board_stalemate)
println("\nLegal moves for White (should be none):")
if isempty(moves_stalemate)
println("No legal moves. (This indicates stalemate)")
else
for mov in moves_stalemate
println("- $mov")
end
end
println("Total legal moves: $(length(moves_stalemate))")
println("\n" * "="^40 * "\n")
end
# Run the main test function
testchess()
- Output:
--- Starting Position --- a b c d e f g h +-----------------+ 8| r n b q k b n r |8 7| p p p p p p p p |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| P P P P P P P P |2 1| R N B Q K B N R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White: - a2a3 - a2a4 - b2b3 - b2b4 - c2c3 - c2c4 - d2d3 - d2d4 - e2e3 - e2e4 - f2f3 - f2f4 - g2g3 - g2g4 - h2h3 - h2h4 - b1a3 - b1c3 - g1f3 - g1h3 Total legal moves: 20 ======================================== --- Position with Black in Check --- a b c d e f g h +-----------------+ 8| . . . . k . . . |8 7| . . . . . . . . |7 6| . . . . . . . . |6 5| . . . . . . . Q |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| . . . . . . . . |2 1| . . . . K . . . |1 +-----------------+ a b c d e f g h Current turn: Black Castling rights: - Is Black king in check? true Legal moves for Black (to get out of check or make other moves): - e8d8 - e8f8 - e8d7 - e8e7 Total legal moves: 4 ======================================== --- Mid-game Position (White to move) --- a b c d e f g h +-----------------+ 8| r . . . k . . r |8 7| p . p p q p b . |7 6| b n . . p n . p |6 5| . . . P P . p . |5 4| . p . . P . . . |4 3| . . N . . N . . |3 2| P P P B B P P P |2 1| R . . Q K . . R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White: - d5d6 - d5e6 - e5f6 - c3b5 - c3a4 - c3b1 - f3g5 - f3d4 - f3h4 - f3g1 - a2a3 - a2a4 - b2b3 - d2c1 - d2e3 - d2f4 - d2g5 - e2f1 - e2d3 - e2c4 - e2b5 - e2a6 - g2g3 - g2g4 - h2h3 - h2h4 - a1b1 - a1c1 - d1c1 - d1b1 - e1f1 - e1g1 - h1g1 - h1f1 Total legal moves: 34 ======================================== --- Position Allowing White Castling --- a b c d e f g h +-----------------+ 8| r . . . k . . r |8 7| . . . . . . . . |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| . . . . . . . . |2 1| R . . . K . . R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White (including castling): - a1b1 - a1c1 - a1d1 - a1a2 - a1a3 - a1a4 - a1a5 - a1a6 - a1a7 - a1a8 - e1d2 - e1e2 - e1f2 - e1d1 - e1f1 - e1g1 - e1c1 - h1g1 - h1f1 - h1h2 - h1h3 - h1h4 - h1h5 - h1h6 - h1h7 - h1h8 Total legal moves: 26 ======================================== --- Position Allowing Pawn Promotion --- a b c d e f g h +-----------------+ 8| . . . . . . . . |8 7| . . . . P . . k |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| . . . . . . . . |2 1| R . . . K . . R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White (including pawn promotions): - e7e8 - e7e8 - e7e8 - e7e8 - a1b1 - a1c1 - a1d1 - a1a2 - a1a3 - a1a4 - a1a5 - a1a6 - a1a7 - a1a8 - e1d2 - e1e2 - e1f2 - e1d1 - e1f1 - e1g1 - e1c1 - h1g1 - h1f1 - h1h2 - h1h3 - h1h4 - h1h5 - h1h6 - h1h7 Total legal moves: 29 ======================================== --- Position Allowing En Passant --- a b c d e f g h +-----------------+ 8| r n b q k b n r |8 7| p p p . p . p p |7 6| . . . . . . . . |6 5| . . . p P p . . |5 4| . . . . . . . . |4 3| . . . . . . . . |3 2| P P P P . P P P |2 1| R N B Q K B N R |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: KQkq Legal moves for White (including en passant capture): - e5e6 - e5f6 - a2a3 - a2a4 - b2b3 - b2b4 - c2c3 - c2c4 - d2d3 - d2d4 - f2f3 - f2f4 - g2g3 - g2g4 - h2h3 - h2h4 - b1a3 - b1c3 - d1e2 - d1f3 - d1g4 - d1h5 - e1e2 - f1e2 - f1d3 - f1c4 - f1b5 - f1a6 - g1f3 - g1h3 - g1e2 Total legal moves: 31 ======================================== --- Stalemate Position --- a b c d e f g h +-----------------+ 8| . . . . . . . . |8 7| . . . . . . . . |7 6| . . . . . . . . |6 5| . . . . . . . . |5 4| . . . . . . . . |4 3| . . . . . . k . |3 2| . . . . . b . . |2 1| . . . . . . . K |1 +-----------------+ a b c d e f g h Current turn: White Castling rights: - Legal moves for White (should be none): No legal moves. (This indicates stalemate) Total legal moves: 0 ========================================
Primarily written to see if I could find all moves with one regex. The answer was "mostly", the main problem being some moves require history (the current state of the board is not sufficient for castling and en passant). I also wanted to try different methods of making moves. It does not play well, but then neither do I.
#!/usr/bin/perl
use strict;
use warnings;
use Tk;
use Tk::ROText;
use List::Util qw( any sum0 shuffle first );
my $startingposition = our $board = <<END;
rnbqkbnr
pppppppp
--------
--------
--------
--------
PPPPPPPP
RNBQKBNR
END
my $size = 80;
my $message = 'Initializing...';
my ($from, $moving, $over);
my (%legal, %canmove, @previous, $castleleft, $castleright, $enpassant);
my @location = map { my $row = $_; map "$_$row", 'a' .. 'i' } reverse 1 .. 8;
my %values = qw( - 0 p 100 n 350 b 350 r 525 q 1e3 k 1e4);
my %names = qw(p pawn r rook n knight b bishop q queen k king);
our @moves;
my $g = qr/.{8}/s;
my $gm = qr/.{9}/s;
my $gp = qr/.{7}/s;
my $gpp = qr/.{6}/s;
my $opp = qr/[a-z]/;
my $oppe = qr/[a-z-]/;
my $whitemoves = qr/(?|
(?| # forward
(Q|R) (?: -* | $g (?:- $g)* ) ($oppe) # rectangular
| (Q|B) (?: $gp (?:- $gp)* | $gm (?:- $gm)* ) ($oppe) # diagonal
| (K) (?: | $gp | $g | $gm ) ($oppe)
| (N) (?: $gm . $g | $gp . $g | . $gm | $gpp (?=..) ) ($oppe)
) (?{ push @moves, [$1, @-[1,2], $2] })
|
(?| # backward
($oppe) (?: -* | $g (?:- $g)* ) (Q|R) # rectangular
| ($oppe) (?: $gp (?:- $gp)* | $gm (?:- $gm)* ) (Q|B) # diagonal
| ($oppe) (?: | $gp | $g | $gm ) (K)
| ($oppe) (?: $gm . $g | $gp . $g | . $gm | $gpp (?=..) ) (N)
| (-) $g (P)
| ($opp) (?: $gm | $gp ) (P)
) (?{ push @moves, [$2, @-[2,1], $1] })
|
(-) $g (-) $g (P) .*\n.{8}$ (?{ push @moves, [$3, @-[3,1], $1, $-[2]] })
) (*FAIL) /x;
$opp = qr/[A-Z]/;
$oppe = qr/[A-Z-]/;
my $blackmoves = qr/(?|
(?| # forward
(q|r) (?: -* | $g (?:- $g)* ) ($oppe) # rectangular
| (q|b) (?: $gp (?:- $gp)* | $gm (?:- $gm)* ) ($oppe) # diagonal
| (k) (?: | $gp | $g | $gm ) ($oppe)
| (n) (?: $gm . $g | $gp . $g | . $gm | $gpp (?=..) ) ($oppe)
| (p) $g (-)
| (p) (?: $gm | $gp ) ($opp)
) (?{ push @moves, [$1, @-[1,2], $2] })
|
^.{8}\n.* (p) $g (-) $g (-) (?{ push @moves, [$1, @-[1,3], $3, $-[2]] })
|
(?| # backward
($oppe) (?: -* | $g (?:- $g)* ) (q|r) # rectangular
| ($oppe) (?: $gp (?:- $gp)* | $gm (?:- $gm)* ) (q|b) # diagonal
| ($oppe) (?: | $gp | $g | $gm ) (k)
| ($oppe) (?: $gm . $g | $gp . $g | . $gm | $gpp (?=..) ) (n)
) (?{ push @moves, [$2, @-[2,1], $1] })
) (*FAIL) /x;
my $mw = MainWindow->new;
$mw->title( 'Chess' );
my $label = $mw->Label( -textvariable => \$message, -font => 'times 20',
)->pack(-fill => 'x');
$mw->Frame(-height => 20, -bg => 'darkblue',
)->pack(-fill => 'x', -expand => 1);
my $grid = $mw->Frame->pack;
my @squares = map { my $me = $_; $_ % 9 == 8 ? 'oops' :
do { my $w = $grid->Canvas( -width => $size, -height => $size,
-bd => 0, -relief => 'flat', -highlightthickness => 0,
-bg => ($_ % 9 + int $_ / 9) % 2 ? 'brown3' : 'brown2',
)->grid( -row => 1 + int $_ / 9, -column => 1 + $_ % 9 );
$w->Tk::bind('<ButtonRelease-4>' => sub{$w->yviewMoveto(0)} );
$w->Tk::bind('<ButtonRelease-5>' => sub{$w->yviewMoveto(0)} );
$w->Tk::bind('<1>' => sub { click($me) } );
$w }
} 0 .. 71;
for my $n (0 .. 7)
{
$grid->Label(-text => $n + 1,
)->grid( -row => 8 - $n, -column => $_) for 0, 9;
$grid->Label(-text => ('a' ... 'h')[$n],
)->grid( -row => $_, -column => 1 + $n) for 0, 9;
}
$mw->Frame(-height => 20, -bg => 'darkblue',
)->pack(-fill => 'x', -expand => 1);
$mw->Button(-text => $_->[0], -command => $_->[1], -font => 24,
)->pack( -side => 'left', -fill => 'x', -expand => 1) for
[Restart => \&restart],
['Previous State' => \&previous],
['Random Move' => \&random],
[Help => \&help],
[Exit => sub {$mw->destroy}];
restart();
MainLoop;
-M $0 < 0 and exec $0, @ARGV;
sub restart
{
$from = $over = undef;
$enpassant = -1;
$castleleft = $castleright = 1;
@previous =
[ ($board = $startingposition), $castleleft, $castleright, $enpassant ];
show( $board );
$message = (incheck($board, 1) && "** IN CHECK ** ") . 'White to move';
$label->configure(-bg => 'gray85');
$label->configure(-fg => 'black');
findlegal();
}
sub previous
{
$over and $mw->bell, return;
@previous and ($board, $castleleft, $castleright, $enpassant) =
@{ pop @previous };
show($board);
findlegal();
}
sub random
{
$over || keys %legal == 0 and $mw->bell, return;
($from, my $to) = split ' ', (keys %legal)[rand keys %legal];
# ($from, my $to) = map @$_,
# (sort { $values{substr $board, $b->[1], 1} <=>
# $values{substr $board, $a->[1], 1} }
# map [ split ],
# shuffle keys %legal)[0];
$moving = substr $board, $from, 1;
click($to);
}
sub click
{
$over and $mw->bell, return;
my $pos = shift;
my $piece = substr $board, $pos, 1;
if( defined $from )
{
if( $piece eq 'R' and $legal{"$from $pos"} and $from == 67 and
$pos == 63 || $pos == 70 ) # castle
{
push @previous, [ $board, $castleleft, $castleright, $enpassant ];
$pos == 63 ? $board =~ s/R---K/--KR-/ : $board =~ s/K--R/-RK-/;
$castleright = $castleleft = 0;
playblack();
}
elsif( $pos == $enpassant and $piece eq '-' and
$from == $enpassant + 8 and substr($board, $from, 1) eq 'P' )
{
substr($board, $enpassant, 10) =~ s/-(.{7})Pp/P$1--/s
or die "enpassant";
$enpassant = -1;
playblack();
}
elsif( $pos == $enpassant and $piece eq '-' and
$from == $enpassant + 10 and substr($board, $from, 1) eq 'P' )
{
substr($board, $enpassant, 11) =~ s/-(.{8})pP/P$1--/s
or die "enpassant";
$enpassant = -1;
playblack();
}
elsif( $piece =~ /[a-z-]/ and $legal{"$from $pos"} )
{
push @previous, [ $board, $castleleft, $castleright, $enpassant ];
substr $board, $from, 1, '-';
substr $board, $pos, 1, $moving;
1 while $board =~ s/^.*\KP/Q/; # promotion
$board =~ s/p(?=.*$)/q/g; # promotion
$from == 67 and $castleleft = $castleright = 0; # no castle king
$from == 63 and $castleleft = 0; # left rook
$from == 70 and $castleright = 0; # right rook
playblack();
}
else { $mw->bell }
$from = $piece = undef;
if( not $over )
{
$message = 'White to move';
$label->configure(-bg => 'gray85');
findlegal();
if( ! $over and incheck($board, 1) )
{
$message =~ s/^/** IN CHECK ** /;
$label->configure(-bg => 'yellow');
}
}
show($board);
}
elsif( $piece =~ /[A-Z]/ and $canmove{$pos} )
{
$from = $pos;
$moving = $piece;
$message = "White moving $names{lc $moving} from $location[$from]";
$squares[$from]->itemconfigure('all', -fill => 'yellow');
}
else
{
$piece =~ /[A-Z]/ and $mw->bell;
$from = $piece = undef;
findlegal();
$message = 'White to move';
show($board);
}
}
sub scale { map $size * $_ >> 3, @_ };
sub show
{
while( $board =~ /./g )
{
my $c = $squares[ my $pos = $-[0] ];
my $char = uc $&;
my $color = $& =~ /[A-Z]/ ? 'white' : 'black';
$c->delete('all');
if( $char eq 'P' )
{
$c->createOval(scale(3, 3, 5, 5));
$c->createArc(scale(2, 4.8, 6, 9), -start => 0, -extent => 180);
$c->itemconfigure('all', -outline => undef);
}
elsif( $char eq 'N' )
{
$c->createPolygon( scale(2, 7, 1, 4, 3, 1, 7, 4, 6, 5, 4, 4, 5.5, 7));
}
elsif( $char eq 'K' )
{
$c->createPolygon( scale(1, 7, 3.5, 4, 3.5, 3, 2.5, 3, 2.5,
2, 3.5, 2, 3.5, 1, 4.5, 1, 4.5, 2, 5.5, 2, 5.5, 3, 4.5, 3, 4.5,
4, 7, 7));
$c->createArc( scale(1, 4, 4, 10), -start => 60, -extent => 120,
-outline => undef);
$c->createArc( scale(4, 4, 7, 10), -start => 0, -extent => 120,
-outline => undef);
}
elsif( $char eq 'Q' )
{
$c->createPolygon( scale(2, 7, 1, 2, 3, 5, 4, 1, 5, 5, 7, 2, 6, 7));
}
elsif( $char eq 'R' )
{
$c->createPolygon( scale(1, 7, 2, 3, 1, 3, 1, 1,
2, 1, 2, 2, 3, 2, 3, 1, 5, 1, 5, 2, 6, 2, 6, 1,
7, 1, 7, 3, 6, 3, 7, 7));
}
elsif( $char eq 'B' )
{
$c->createPolygon(scale(3, 7, 2, 6, 4, 1, 6, 6, 5, 7));
$c->createOval(scale(3.5, 1, 4.5, 2), -outline => undef);
}
$c->itemconfigure('all', -fill => $color);
}
}
sub newboard
{
my ($piece, $from, $to, $was) = @{ +shift };
my $newboard = $board;
substr $newboard, $from, 1, '-';
substr $newboard, $to, 1, $piece;
$newboard;
}
sub incheck # board, 1=whiteincheck 0=blackincheck
{
my ($newboard, $who) = @_;
local @moves;
$newboard =~ ( $who ? $blackmoves : $whitemoves );
any { $_->[3] =~ /k/i } @moves;
}
sub blink
{
my $pos = shift;
$message = 'Black moving...';
for ( ('green', 'red') x 2 )
{
$squares[$pos]->itemconfigure('all', -fill => $_);
$mw->update;
select undef, undef, undef, 0.1;
}
}
sub findlegal
{
local @moves;
$board =~ $whitemoves;
%legal = %canmove = ();
$legal{ $_->[1] . ' ' . $_->[2] } = $canmove{$_->[1]} = 1 for
grep { ! incheck(newboard($_), 1) } @moves;
@moves = ();
if( $castleleft and $board =~ /R---K...\n\z/ )
{
$board =~ $blackmoves;
my $attack = any { $_->[2] =~ /6[567]/ } @moves;
$attack or $legal{"67 63"} = $canmove{67} = 1;
}
if( $castleright and $board =~ /K--R\n\z/ )
{
@moves or $board =~ $blackmoves;
my $attack = any { $_->[2] =~ /6[789]/ } @moves;
$attack or $legal{"67 70"} = $canmove{67} = 1;
}
if( $enpassant > 0 )
{
substr($board, $enpassant + $_, 1) eq 'P' and
$legal{$enpassant + $_ . " $enpassant"} = $canmove{$enpassant + $_} = 1
for 8, 10;
}
if( not %legal )
{
$over = 1;
$message = incheck($board, 1) ? "CHECKMATE" : "DRAW";
$label->configure(-bg => 'red');
$label->configure(-fg => 'white');
}
}
sub islegal { $legal{"@_"} }
sub score
{
my $bb = newboard(shift);
sum0 map(-$values{+lc}, $bb =~ /[A-Z]/g), map $values{$_}, $bb =~ /[a-z]/g;
}
sub lookahead
{
my $bb = shift;
local @moves;
$bb =~ $blackmoves;
# print "black moves : " . @moves, "\n";
my @bbest;
for my $bmove ( @moves )
{
my $freedom;
local $board = newboard($bmove);
local @moves;
$board =~ $whitemoves;
$freedom = @moves;
my @wbest;
for my $wmove ( @moves )
{
local $board = newboard($wmove);
local @moves;
$board =~ $blackmoves;
my @bbest2;
for my $bmove2 ( @moves )
{
push @bbest2, [ $bmove, score($bmove2), $freedom ];
}
push @wbest, first { not incheck( newboard($wmove, 0) ) }
sort { $b->[1] <=> $a->[1] } shuffle @bbest2;
}
push @bbest, first { not incheck( newboard($bmove, 1) ) }
sort { $a->[1] <=> $b->[1] }
grep defined $_->[1],
shuffle @wbest;
}
map $_->[0], sort { $b->[1] <=> $a->[1] or $b->[2] <=> $a->[2] }
grep defined $_->[1],
shuffle @bbest;
}
sub playblack
{
show($board);
$message = 'Black thinking...';
$label->configure(-bg => 'gray85');
$mw->update;
@moves = lookahead($board);
my $themove = first { ! incheck(newboard($_), 0) } @moves;
if( not $themove )
{
$over = 1;
$message = incheck( $board, 0 ) ? "CHECKMATE" : "DRAW";
$label->configure(-bg => 'red');
$label->configure(-fg => 'white');
return;
}
blink( $themove->[1] );
$board = newboard $themove;
$enpassant = $themove->[4] // -1;
1 while $board =~ s/^.*\KP/Q/;
$board =~ s/p(?=.*$)/q/g;
show($board);
}
sub help
{
my $help = $mw->Toplevel;
$help->title("Chess Help");
my $ro = $help->ROText( -font => 'times 14', -height => 12, -width => 60,
)->pack;
$help->Button(-text => 'Dismiss', -command => sub {$help->destroy},
)->pack(-fill => 'x');
$ro->insert(end => <<END);
You are playing White, the program is playing Black.
To move or capture : left click on piece to move,
it should turn yellow if a legal move for that piece exists,
then left click on the destination square.
To castle : left click on the King, then left click on a Rook.
To capture "en passant" : left click on your Pawn,
then left click on the square the opponent's Pawn skipped over.
END
}
Version 0.8.1+ contains demo\rosetta\chess.exw, a slightly cleaned-up copy of a 20-year old translation of TSCP.
It isn't particularly good (though perhaps a reasonable starting point for something better), at over 1,600 lines it does not really bear any useful comparison to the lisp version, and is simply not worth posting on this site, especially in light of potential copyright issues.
This implementation supports all chess rules (including castling, pawn promotion and en passant), switching sides, unlimited undo/redo, and the setup, saving and loading of board positions to/from files.
# *Board a1 .. h8
# *White *Black *WKPos *BKPos *Pinned
# *Depth *Moved *Undo *Redo *Me *You
(load "@lib/simul.l")
### Fields/Board ###
# x y color piece whAtt blAtt
(setq *Board (grid 8 8))
(for (X . Lst) *Board
(for (Y . This) Lst
(=: x X)
(=: y Y)
(=: color (not (bit? 1 (+ X Y)))) ) )
(de *Straight `west `east `south `north)
(de *Diagonal
((This) (: 0 1 1 0 -1 1)) # Southwest
((This) (: 0 1 1 0 -1 -1)) # Northwest
((This) (: 0 1 -1 0 -1 1)) # Southeast
((This) (: 0 1 -1 0 -1 -1)) ) # Northeast
(de *DiaStraight
((This) (: 0 1 1 0 -1 1 0 -1 1)) # South Southwest
((This) (: 0 1 1 0 -1 1 0 1 1)) # West Southwest
((This) (: 0 1 1 0 -1 -1 0 1 1)) # West Northwest
((This) (: 0 1 1 0 -1 -1 0 -1 -1)) # North Northwest
((This) (: 0 1 -1 0 -1 -1 0 -1 -1)) # North Northeast
((This) (: 0 1 -1 0 -1 -1 0 1 -1)) # East Northeast
((This) (: 0 1 -1 0 -1 1 0 1 -1)) # East Southeast
((This) (: 0 1 -1 0 -1 1 0 -1 1)) ) # South Southeast
### Pieces ###
(de piece (Typ Cnt Fld)
(prog1
(def
(pack (mapcar '((Cls) (cdr (chop Cls))) Typ))
Typ )
(init> @ Cnt Fld) ) )
(class +White)
# color ahead
(dm init> (Cnt Fld)
(=: ahead north)
(extra Cnt Fld) )
(dm name> ()
(pack " " (extra) " ") )
(dm move> (Fld)
(adjMove '*White '*WKPos whAtt- whAtt+) )
(class +Black)
# color ahead
(dm init> (Cnt Fld)
(=: color T)
(=: ahead south)
(extra Cnt Fld) )
(dm name> ()
(pack '< (extra) '>) )
(dm move> (Fld)
(adjMove '*Black '*BKPos blAtt- blAtt+) )
(class +piece)
# cnt field attacks
(dm init> (Cnt Fld)
(=: cnt Cnt)
(move> This Fld) )
(dm ctl> ())
(class +King +piece)
(dm name> () 'K)
(dm val> () 120)
(dm ctl> ()
(unless (=0 (: cnt)) -10) )
(dm moves> ()
(make
(unless
(or
(n0 (: cnt))
(get (: field) (if (: color) 'whAtt 'blAtt)) )
(tryCastle west T)
(tryCastle east) )
(try1Move *Straight)
(try1Move *Diagonal) ) )
(dm attacks> ()
(make
(try1Attack *Straight)
(try1Attack *Diagonal) ) )
(class +Castled)
(dm ctl> () 30)
(class +Queen +piece)
(dm name> () 'Q)
(dm val> () 90)
(dm moves> ()
(make
(tryMoves *Straight)
(tryMoves *Diagonal) ) )
(dm attacks> ()
(make
(tryAttacks *Straight)
(tryAttacks *Diagonal T) ) )
(class +Rook +piece)
(dm name> () 'R)
(dm val> () 47)
(dm moves> ()
(make (tryMoves *Straight)) )
(dm attacks> ()
(make (tryAttacks *Straight)) )
(class +Bishop +piece)
(dm name> () 'B)
(dm val> () 33)
(dm ctl> ()
(when (=0 (: cnt)) -10) )
(dm moves> ()
(make (tryMoves *Diagonal)) )
(dm attacks> ()
(make (tryAttacks *Diagonal T)) )
(class +Knight +piece)
(dm name> () 'N)
(dm val> () 28)
(dm ctl> ()
(when (=0 (: cnt)) -10) )
(dm moves> ()
(make (try1Move *DiaStraight)) )
(dm attacks> ()
(make (try1Attack *DiaStraight)) )
(class +Pawn +piece)
(dm name> () 'P)
(dm val> () 10)
(dm moves> ()
(let (Fld1 ((: ahead) (: field)) Fld2 ((: ahead) Fld1))
(make
(and
(tryPawnMove Fld1 Fld2)
(=0 (: cnt))
(tryPawnMove Fld2 T) )
(tryPawnCapt (west Fld1) Fld2 (west (: field)))
(tryPawnCapt (east Fld1) Fld2 (east (: field))) ) ) )
(dm attacks> ()
(let Fld ((: ahead) (: field))
(make
(and (west Fld) (link @))
(and (east Fld) (link @)) ) ) )
### Move Logic ###
(de inCheck (Color)
(if Color (get *BKPos 'whAtt) (get *WKPos 'blAtt)) )
(de whAtt+ (This Pce)
(=: whAtt (cons Pce (: whAtt))) )
(de whAtt- (This Pce)
(=: whAtt (delq Pce (: whAtt))) )
(de blAtt+ (This Pce)
(=: blAtt (cons Pce (: blAtt))) )
(de blAtt- (This Pce)
(=: blAtt (delq Pce (: blAtt))) )
(de adjMove (Var KPos Att- Att+)
(let (W (: field whAtt) B (: field blAtt))
(when (: field)
(put @ 'piece NIL)
(for F (: attacks) (Att- F This)) )
(nond
(Fld (set Var (delq This (val Var))))
((: field) (push Var This)) )
(ifn (=: field Fld)
(=: attacks)
(put Fld 'piece This)
(and (isa '+King This) (set KPos Fld))
(for F (=: attacks (attacks> This)) (Att+ F This)) )
(reAtttack W (: field whAtt) B (: field blAtt)) ) )
(de reAtttack (W W2 B B2)
(for This W
(unless (memq This W2)
(for F (: attacks) (whAtt- F This))
(for F (=: attacks (attacks> This)) (whAtt+ F This)) ) )
(for This W2
(for F (: attacks) (whAtt- F This))
(for F (=: attacks (attacks> This)) (whAtt+ F This)) )
(for This B
(unless (memq This B2)
(for F (: attacks) (blAtt- F This))
(for F (=: attacks (attacks> This)) (blAtt+ F This)) ) )
(for This B2
(for F (: attacks) (blAtt- F This))
(for F (=: attacks (attacks> This)) (blAtt+ F This)) ) )
(de try1Move (Lst)
(for Dir Lst
(let? Fld (Dir (: field))
(ifn (get Fld 'piece)
(link (list This (cons This Fld)))
(unless (== (: color) (get @ 'color))
(link
(list This
(cons (get Fld 'piece))
(cons This Fld) ) ) ) ) ) ) )
(de try1Attack (Lst)
(for Dir Lst
(and (Dir (: field)) (link @)) ) )
(de tryMoves (Lst)
(for Dir Lst
(let Fld (: field)
(loop
(NIL (setq Fld (Dir Fld)))
(T (get Fld 'piece)
(unless (== (: color) (get @ 'color))
(link
(list This
(cons (get Fld 'piece))
(cons This Fld) ) ) ) )
(link (list This (cons This Fld))) ) ) ) )
(de tryAttacks (Lst Diag)
(use (Pce Cls Fld2)
(for Dir Lst
(let Fld (: field)
(loop
(NIL (setq Fld (Dir Fld)))
(link Fld)
(T
(and
(setq Pce (get Fld 'piece))
(<> (: color) (get Pce 'color)) ) )
(T (== '+Pawn (setq Cls (last (type Pce))))
(and
Diag
(setq Fld2 (Dir Fld))
(= (get Fld2 'y) (get ((get Pce 'ahead) Fld) 'y))
(link Fld2) ) )
(T (memq Cls '(+Knight +Queen +King)))
(T (and Pce (xor Diag (== Cls '+Bishop)))) ) ) ) ) )
(de tryPawnMove (Fld Flg)
(unless (get Fld 'piece)
(if Flg
(link (list This (cons This Fld)))
(for Cls '(+Queen +Knight +Rook +Bishop)
(link
(list This
(cons This)
(cons
(piece (list (car (type This)) Cls) (: cnt))
Fld ) ) ) ) ) ) )
(de tryPawnCapt (Fld1 Flg Fld2)
(if (get Fld1 'piece)
(unless (== (: color) (get @ 'color))
(if Flg
(link
(list This
(cons (get Fld1 'piece))
(cons This Fld1) ) )
(for Cls '(+Queen +Knight +Rook +Bishop)
(link
(list This
(cons (get Fld1 'piece))
(cons This)
(cons
(piece (list (car (type This)) Cls) (: cnt))
Fld1 ) ) ) ) ) )
(let? Pce (get Fld2 'piece)
(and
(== Pce (car *Moved))
(= 1 (get Pce 'cnt))
(isa '+Pawn Pce)
(n== (: color) (get Pce 'color))
(link (list This (cons Pce) (cons This Fld1))) ) ) ) )
(de tryCastle (Dir Long)
(use (Fld1 Fld2 Fld Pce)
(or
(get (setq Fld1 (Dir (: field))) 'piece)
(get Fld1 (if (: color) 'whAtt 'blAtt))
(get (setq Fld2 (Dir Fld1) Fld Fld2) 'piece)
(when Long
(or
(get (setq Fld (Dir Fld)) 'piece)
(get Fld (if (: color) 'whAtt 'blAtt)) ) )
(and
(== '+Rook (last (type (setq Pce (get (Dir Fld) 'piece)))))
(=0 (get Pce 'cnt))
(link
(list This
(cons This)
(cons
(piece (cons (car (type This)) '(+Castled +King)) 1)
Fld2 )
(cons Pce Fld1) ) ) ) ) ) )
(de pinned (Fld Lst Color)
(use (Pce L P)
(and
(loop
(NIL (setq Fld (Dir Fld)))
(T (setq Pce (get Fld 'piece))
(and
(= Color (get Pce 'color))
(setq L
(make
(loop
(NIL (setq Fld (Dir Fld)))
(link Fld)
(T (setq P (get Fld 'piece))) ) ) )
(<> Color (get P 'color))
(memq (last (type P)) Lst)
(cons Pce L) ) ) )
(link @) ) ) )
### Moves ###
# Move ((p1 (p1 . f2)) . ((p1 . f1)))
# Capture ((p1 (p2) (p1 . f2)) . ((p1 . f1) (p2 . f2)))
# Castle ((K (K) (C . f2) (R . f4)) . ((R . f3) (K . f1)))
# Promote ((P (P) (Q . f2)) . ((Q) (P . f1)))
# Capt/Prom ((P (p1) (P) (Q . f2)) . ((Q) (P . f1) (p1 . f2)))
(de moves (Color)
(filter
'((Lst)
(prog2
(move (car Lst))
(not (inCheck Color))
(move (cdr Lst)) ) )
(mapcan
'((Pce)
(mapcar
'((Lst)
(cons Lst
(flip
(mapcar
'((Mov) (cons (car Mov) (get Mov 1 'field)))
(cdr Lst) ) ) ) )
(moves> Pce) ) )
(if Color *Black *White) ) ) )
(de move (Lst)
(if (atom (car Lst))
(inc (prop (push '*Moved (pop 'Lst)) 'cnt))
(dec (prop (pop '*Moved) 'cnt)) )
(for Mov Lst
(move> (car Mov) (cdr Mov)) ) )
### Evaluation ###
(de mate (Color)
(and (inCheck Color) (not (moves Color))) )
(de battle (Fld Prey Attacker Defender)
(use Pce
(loop
(NIL (setq Pce (mini 'val> Attacker)) 0)
(setq Attacker (delq Pce Attacker))
(NIL (and (asoq Pce *Pinned) (not (memq Fld @)))
(max 0 (- Prey (battle Fld (val> Pce) Defender Attacker))) ) ) ) )
# Ref. Sargon, Dan and Kate Spracklen, Hayden 1978
(de cost (Color)
(if (mate (not Color))
-9999
(setq *Pinned
(make
(for Dir *Straight
(pinned *WKPos '(+Rook +Queen))
(pinned *BKPos '(+Rook +Queen) T) )
(for Dir *Diagonal
(pinned *WKPos '(+Bishop +Queen))
(pinned *BKPos '(+Bishop +Queen) T) ) ) )
(let (Ctl 0 Mat 0 Lose 0 Win1 NIL Win2 NIL Flg NIL)
(use (White Black Col Same B)
(for Lst *Board
(for This Lst
(setq White (: whAtt) Black (: blAtt))
((if Color inc dec) 'Ctl (- (length White) (length Black)))
(let? Val (and (: piece) (val> @))
(setq Col (: piece color) Same (== Col Color))
((if Same dec inc) 'Ctl (ctl> (: piece)))
(unless
(=0
(setq B
(if Col
(battle This Val White Black)
(battle This Val Black White) ) ) )
(dec 'Val 5)
(if Same
(setq
Lose (max Lose B)
Flg (or Flg (== (: piece) (car *Moved))) )
(when (> B Win1)
(xchg 'B 'Win1)
(setq Win2 (max Win2 B)) ) ) )
((if Same dec inc) 'Mat Val) ) ) ) )
(unless (=0 Lose) (dec 'Lose 5))
(if Flg
(* 4 (+ Mat Lose))
(when Win2
(dec 'Lose (>> 1 (- Win2 5))) )
(+ Ctl (* 4 (+ Mat Lose))) ) ) ) )
### Game ###
(de display (Res)
(when Res
(disp *Board T
'((This)
(cond
((: piece) (name> @))
((: color) " - ")
(T " ") ) ) ) )
(and (inCheck *You) (prinl "(+)"))
Res )
(de moved? (Lst)
(or
(> 16 (length Lst))
(find '((This) (n0 (: cnt))) Lst) ) )
(de bookMove (From To)
(let Pce (get From 'piece)
(list 0 (list (list Pce (cons Pce To)) (cons Pce From))) ) )
(de myMove ()
(let? M
(cadr
(cond
((moved? (if *Me *Black *White))
(game *Me *Depth moves move cost) )
(*Me
(if (member (get *Moved 1 'field 'x) (1 2 3 5))
(bookMove 'e7 'e5)
(bookMove 'd7 'd5) ) )
((rand T) (bookMove 'e2 'e4))
(T (bookMove 'd2 'd4)) ) )
(move (car (push '*Undo M)))
(off *Redo)
(cons
(caar M)
(cdr (asoq (caar M) (cdr M)))
(pick cdr (cdar M)) ) ) )
(de yourMove (From To Cls)
(when
(find
'((Mov)
(and
(== (caar Mov) (get From 'piece))
(== To (pick cdr (cdar Mov)))
(or
(not Cls)
(isa Cls (car (last (car Mov)))) ) ) )
(moves *You) )
(prog1 (car (push '*Undo @))
(off *Redo)
(move @) ) ) )
(de undo ()
(move (cdr (push '*Redo (pop '*Undo)))) )
(de redo ()
(move (car (push '*Undo (pop '*Redo)))) )
(de setup (Depth You Init)
(setq *Depth (or Depth 5) *You You *Me (not You))
(off *White *Black *Moved *Undo *Redo)
(for Lst *Board
(for This Lst (=: piece) (=: whAtt) (=: blAtt)) )
(if Init
(for L Init
(with (piece (cadr L) 0 (car L))
(unless (caddr L)
(=: cnt 1)
(push '*Moved This) ) ) )
(mapc
'((Cls Lst)
(piece (list '+White Cls) 0 (car Lst))
(piece '(+White +Pawn) 0 (cadr Lst))
(piece '(+Black +Pawn) 0 (get Lst 7))
(piece (list '+Black Cls) 0 (get Lst 8)) )
'(+Rook +Knight +Bishop +Queen +King +Bishop +Knight +Rook)
*Board ) ) )
(de main (Depth You Init)
(setup Depth You Init)
(display T) )
(de go Args
(display
(cond
((not Args) (xchg '*Me '*You) (myMove))
((== '- (car Args)) (and *Undo (undo)))
((== '+ (car Args)) (and *Redo (redo)))
((apply yourMove Args) (display T) (myMove)) ) ) )
# Print position to file
(de ppos (File)
(out File
(println
(list 'main *Depth *You
(lit
(mapcar
'((This)
(list
(: field)
(val This)
(not (memq This *Moved)) ) )
(append *White *Black) ) ) ) ) ) )Start:
$ pil chess.l -main +
+---+---+---+---+---+---+---+---+
8 |<R>|<N>|<B>|<Q>|<K>|<B>|<N>|<R>|
+---+---+---+---+---+---+---+---+
7 |<P>|<P>|<P>|<P>|<P>|<P>|<P>|<P>|
+---+---+---+---+---+---+---+---+
6 | | - | | - | | - | | - |
+---+---+---+---+---+---+---+---+
5 | - | | - | | - | | - | |
+---+---+---+---+---+---+---+---+
4 | | - | | - | | - | | - |
+---+---+---+---+---+---+---+---+
3 | - | | - | | - | | - | |
+---+---+---+---+---+---+---+---+
2 | P | P | P | P | P | P | P | P |
+---+---+---+---+---+---+---+---+
1 | R | N | B | Q | K | B | N | R |
+---+---+---+---+---+---+---+---+
a b c d e f g h
Entering moves:
: (go e2 e4)Undo moves:
: (go -)Redo:
: (go +)Switch sides:
: (go)Save position to a file:
: (ppos "file")Load position from file:
: (load "file")"Python Chess" is a chess game at the PyGame-Website and Homepage.
There is a 3D-Chess-Board in the VPython contributed section.
A very simple chess engine using python-chess. The computer plays Black. The program uses a two-ply search which computes material value for both sides and its own piece mobility after Black and White have made their moves.
The default Unicode board may look wonky and misaligned with certain terminal fonts. To use an ASCII board instead (like in the output shown below), set UNICODE = False. If your terminal uses dark mode, set DARKMODE = True.
Increasing RANDFAC, e.g. to 10 or even 100, creates more variety in computer moves, so that there is less repetition in games and openings.
The computer may say some things that allude to the chess game in 2001: A Space Odyssey, by the way.
# Simple Python chess engine
# Computer plays Black
import sys, random, chess
from collections import Counter
UNICODE = True # Print board with Unicode symbols?
DARKMODE = False # Invert symbol colors?
RANDFAC = 1 # Randomness factor
board = chess.Board()
def hal9000():
print("Thank you for a very enjoyable game.")
def pboard():
"Print board"
if UNICODE and DARKMODE:
print(board.unicode(invert_color=True))
elif UNICODE:
print(board.unicode())
else:
print(board)
pboard()
while not board.outcome():
while True:
try:
move = input("Your move? ")
if move in ("q", "quit", "resign", "exit"):
hal9000()
sys.exit()
board.push_uci(move)
except ValueError: print("Sorry?")
else: break
moves = {}
for mymove in board.legal_moves:
board.push(mymove)
if board.result() == "0-1": # Can Black win? If so, end the game.
print(mymove)
pboard()
print("I'm sorry, Frank. I think you missed it:")
pm = board.peek()
pn = chess.piece_name(board.piece_at(pm.to_square).piece_type)
ps = chess.square_name(pm.to_square)
print(f"{pn.capitalize()} to {ps}, mate.")
hal9000()
sys.exit()
for yourmove in board.legal_moves:
board.push(yourmove)
if board.result() == "1-0": # Has White won? If so, avoid move.
board.pop()
moves[mymove] = -1000
break
v = Counter(board.fen().split()[0])
p = (9 * (v['q']-v['Q']) + 5 * (v['r']-v['R']) + 3 * (v['b']-v['B'])
+ 3 * (v['n']-v['N']) + v['p'] - v['P'])
mobility = len(list(board.legal_moves)) + RANDFAC * random.random()
p += mobility / 1000
#print(mymove, yourmove, p)
old = moves.get(mymove, 1e6)
if p < old: moves[mymove] = p
board.pop()
board.pop()
try: sel = sorted(moves.items(), key=lambda item: -item[1])[0][0]
except: break
print(sel)
board.push(sel)
pboard()
print(f"Game finished, result is {board.result()}")
hal9000()
- Output:
(in ASCII)
$ python3 simplechess.py r n b q k b n r p p p p p p p p . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P P P P P P P P R N B Q K B N R Your move? e2e4 e7e6 r n b q k b n r p p p p . p p p . . . . p . . . . . . . . . . . . . . . P . . . . . . . . . . . P P P P . P P P R N B Q K B N R Your move? g1f3 d8f6 r n b . k b n r p p p p . p p p . . . . p q . . . . . . . . . . . . . . P . . . . . . . . N . . P P P P . P P P R N B Q K B . R Your move? …
Here is the PGN of a full game against Stockfish. Like many simple chess engines, it has an unfortunate tendency to rush out with its Queen early in the game, because that kind of move looks wonderful to the computer in terms of maximizing piece mobility. But unfortunately the Queen is often in danger there, leading to its loss:
[Event "Stockfish vs Python World Championship"] [Site "Rosetta Code"] [Date "2022.05.08"] [Round "1"] [White "Stockfish"] [Black "Python Simple Chess"] [Result "1-0"] 1.e4 e6 2.Nf3 Qf6 3.Nc3 Qf4 4.d4 Qg4 5.Be2 Qxg2 6.Rg1 Qh3 7.Bg5 Nc6 8.Rg3 Qh5 9.Nh4 Qxg5 10.Rxg5 Bd6 11.Rxg7 Nf6 12.e5 Bxe5 13.dxe5 Nxe5 14.Qd4 Ke7 15.Qxe5 Ne8 16.Qg5+ Kd6 17.O-O-O+ Kc6 18.Qb5# 1-0
Opening play could be improved a lot by using book moves, which is easy to do in python-chess with its Polyglot support.
Here is an example of a won game against a random mover chess bot, just to show this Python engine can actually win, provided its opponent is inept enough. (Human chess beginners tend to play on a random mover level, so this is a useful benchmark.)
[Event "Rosetta Code Chess Classics"] [Site "Rosetta Code"] [Date "2022.05.08"] [Round "1"] [White "Random Mover"] [Black "Python Simple Chess"] [Result "0-1"] 1.Nf3 e6 2.c4 Qf6 3.Ng1 Qf4 4.h4 Qxc4 5.e3 Qe4 6.Qg4 Qxg4 7.Nh3 Qxh4 8.d3 Bb4+ 9.Bd2 Bd6 10.a4 Nc6 11.Bc3 Qg4 12.Ba5 Nxa5 13.Be2 Qxg2 14.Ng1 Qxh1 15.b4 Qxg1+ 16.Bf1 Bxb4+ 17.Nc3 Bxc3+ 18.Ke2 Bxa1 19.Kd2 Qxf1 20.Kc2 Qxf2+ 21.Kb1 Qb2# 0-1
import "./iterate" for Stepped
import "./fmt" for Fmt
import "./ioutil" for Input, Output
import "./str" for Str
var Board = List.filled(8, null)
// initialize Board
var starting = [
[-500, -270, -300, -900, -7500, -300, -270, -500],
[-100, -100, -100, -100, -100, -100, -100, -100],
[ 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0],
[ 100, 100, 100, 100, 100, 100, 100, 100],
[ 500, 270, 300, 900, 5000, 300, 270, 500]
]
for (x in 0..7) {
Board[x] = List.filled(8, 0)
for (y in 0..7) Board[x][y] = starting[x][y]
}
// best moves
var BestA = List.filled(8, 0)
var BestB = List.filled(8, 0)
var BestX = List.filled(8, 0)
var BestY = List.filled(8, 0)
// current Levels
var Cflag = false
var Level = 0
var MaxLevel = 5
var Score = 0
var End = false
// helper classes
class Terminal {
static clear() {
Output.fwrite("\e[2J")
locate(1, 1)
}
static locate(r, c) {
Output.fwrite("\e[%(r);%(c)H")
}
}
class Color {
static set(fore, back) {
fore = (fore < 8) ? fore + 30 : fore + 82
back = (back < 8) ? back + 40 : back + 92
Output.fwrite("\e[%(fore);%(back)m")
}
static reset() {
Output.fwrite("\e[39;49m")
}
}
class Chess {
// generate list of moves for bishop
static bishop(a, b, xx, yy, ndx) {
var id = Board[b][a].sign
var f = Fn.new { |x, y|
// make sure no piece of same color
if (id != Board[y][x].sign) {
ndx = ndx + 1
xx[ndx] = x
yy[ndx] = y
}
}
// work out diagonal moves in each of four directions
for (dxy in 1..7) {
var x = a - dxy
var y = b + dxy
// stop if go off the board
if (x < 0 || x > 7 || y < 0 || y > 7) break
f.call(x, y)
// stop when hit a piece
if (Board[y][x] != 0) break
}
for (dxy in 1..7) {
var x = a + dxy
var y = b + dxy
if (x < 0 || x > 7 || y < 0 || y > 7) break
f.call(x, y)
if (Board[y][x] != 0) break
}
for (dxy in 1..7) {
var x = a - dxy
var y = b - dxy
if (x < 0 || x > 7 || y < 0 || y > 7) break
f.call(x, y)
if (Board[y][x] != 0) break
}
for (dxy in 1..7) {
var x = a + dxy
var y = b - dxy
if (x < 0 || x > 7 || y < 0 || y > 7) break
f.call(x, y)
if (Board[y][x] != 0) break
}
return ndx
}
// evaluate possible moves
static evaluate(id, prune) {
var xx = List.filled(27, 0)
var yy = List.filled(27, 0)
Level = Level + 1 // update recursion level
var bestScore = 10000 * id
for (b in 7..0) { // loop through each square
for (a in 7..0) {
// if square doesn't have right color piece, go to next square
if (Board[b][a].sign != id) {
if (Level == 1) showman(a, b, 0)
continue
}
if (Level == 1) showman(a, b, 8) // show move currently being tried
var ndx = 0
ndx = moveList(a, b, xx, yy, ndx) // get list of moves for current piece
for (i in Stepped.ascend(0..ndx)) { // loop through each possible move
var x = xx[i]
var y = yy[i]
if (Level == 1) {
Terminal.locate(1, 1)
Fmt.print("Trying: $c$d-$c$d", 65+a, 8-b, 65+x, 8-y)
showman(x, y, 8)
}
var oldScore = Score
var mover = Board[b][a] // store these locations
var target = Board[y][x] // so we can set the move back
makeMove(a, b, x, y) // make the move so we can evaluate
if (Level < MaxLevel) {
var p = bestScore - target + id*(8 - (4-x).abs - (4-y).abs)
Score = Score + evaluate(-id, p)
}
// work out score for move
Score = Score + target - id*(8 - (4-x).abs - (4-y).abs)
if ((id < 0 && Score > bestScore) || (id > 0 && Score < bestScore)) {
// update current best score
BestA[Level] = a
BestB[Level] = b
BestX[Level] = x
BestY[Level] = y
bestScore = Score
if ((id < 0 && bestScore >= prune) ||
(id > 0 && bestScore <= prune)) {
// prune to avoid wasting time
Board[b][a] = mover // restore position prior to modification
Board[y][x] = target
Score = oldScore
if (Level == 1) showman(x, y, 0)
if (Level == 1) showman(a, b, 0)
Level = Level - 1
return bestScore
}
}
Board[b][a] = mover
Board[y][x] = target
Score = oldScore
if (Level == 1) showman(x, y, 0)
}
if (Level == 1) showman(a, b, 0)
}
}
Level = Level - 1
return bestScore
}
// determine whether 'in check' or not
static inCheck() {
var xx = List.filled(27, 0)
var yy = List.filled(27, 0)
var ndx = 0
for (b in 0..7) {
for (a in 0..7) {
if (Board[b][a] >= 0) continue
ndx = moveList(a, b, xx, yy, ndx)
for (i in Stepped.ascend(0..ndx)) {
var x = xx[i]
var y = yy[i]
if (Board[y][x] == 5000) {
System.print("You are in check!\n\n")
return true
}
}
}
}
return false
}
// get player move
static io(a, b, x, y, result) {
var xx = List.filled(27, 0)
var yy = List.filled(27, 0)
Terminal.clear()
if (a >= 0) {
if (result < -2500) {
System.print("I resign")
End = true
return
}
var piece = Board[y][x]
makeMove(a, b, x, y)
// show computer move
Fmt.print("My move: $c$d-$c$d", 65+a, 8-b, 65+x, 8-y)
if (piece != 0) {
System.write("I took your ")
System.print( (piece == 100) ? "pawn" :
(piece == 270) ? "knight" :
(piece == 300) ? "bishop" :
(piece == 500) ? "rook" :
(piece == 900) ? "queen" :
(piece == 5000) ? "king" : "")
}
inCheck()
}
while (true) {
showbd()
Terminal.locate(24, 1)
var inp = Str.upper(Input.text("Your move (ex: E2-E4): "))
if (inp == "QUIT") {
Terminal.clear()
End = true
return
}
// castling, kingside rook
if (inp == "O-O" || inp == "0-0") {
if (Cflag || Board[7][7] != 500 ||
Board[7][6] != 0 || Board[7, 5] != 0) {
Terminal.clear()
continue
}
Board[7][6] = 5000
Board[7][4] = 0
Board[7][5] = 500
Board[7][7] = 0
Cflag = true
return
}
// castling, queenside rook
if (inp == "O-O-O" || inp == "0-0-0") {
if (Cflag || Board[7][0] != 500 ||
Board[7][1] != 0 || Board[7, 2] != 0 || Board[7][3] != 0) {
Terminal.clear()
continue
}
Board[7][2] = 5000
Board[7][4] = 0
Board[7][3] = 500
Board[7][0] = 0
Cflag = true
return
}
if (inp.count < 5) {
Terminal.clear()
continue
}
b = 8 - (inp[1].bytes[0] - 48)
a = inp[0].bytes[0] - 65
x = inp[3].bytes[0] - 65
y = 8 - (inp[4].bytes[0] - 48)
if (b > 7 || b < 0 || a > 7 || a < 0 || x > 7 ||
x < 0 || y > 7 || y < 0 || Board[b][a] <= 0) {
Terminal.clear()
continue
}
var ndx = 0
ndx = moveList(a, b, xx, yy, ndx)
// validate move
for (k in Stepped.ascend(0..ndx)) {
if (x == xx[k] && y == yy[k]) {
var mover = Board[b][a]
var target = Board[y][x]
makeMove(a, b, x, y)
Terminal.locate(1, 1)
// make sure move out of check
if (!inCheck()) return
Board[b][a] = mover // otherwise move out of check and reset board
Board[y][x] = target
Terminal.clear()
break
}
}
Terminal.clear()
}
return
}
// generate list of moves for king
static king(a, b, xx, yy, ndx) {
var id = Board[b][a].sign
// go through each of 8 possible moves, checking for same color and off board
for (dy in -1..1) {
if (b + dy < 0 || b + dy > 7) continue
for (dx in -1..1) {
if (a + dx < 0 || a + dx > 7) continue
if (id != Board[b+dy][a+dx].sign) {
ndx = ndx + 1
xx[ndx] = a + dx
yy[ndx] = b + dy
}
}
}
return ndx
}
// generate list of moves for knight
static knight(a, b, xx, yy, ndx) {
var id = Board[b][a].sign // get color
var f = Fn.new { |x, y|
// make sure on board
if (x < 0 || x > 7 || y < 0 || y > 7) return
// make sure no piece of same color
if (id != Board[y][x].sign) {
ndx = ndx + 1
xx[ndx] = x
yy[ndx] = y
}
}
// work out each of the knight's eight moves
f.call(a - 1, b - 2)
f.call(a - 2, b - 1)
f.call(a + 1, b - 2)
f.call(a + 2, b - 1)
f.call(a - 1, b + 2)
f.call(a - 2, b + 1)
f.call(a + 1, b + 2)
f.call(a + 2, b + 1)
return ndx
}
// make a move on the board
static makeMove(a, b, x, y) {
Board[y][x] = Board[b][a] // move piece to target square
Board[b][a] = 0 // old square now empty
if (y == 0 && Board[y][x] == 100) Board[y][x] = 900 // pawn promoted
if (y == 7 && Board[y][x] == -100) Board[y][x] = -900
}
// generate list of moves for current piece
static moveList(a, b, xx, yy, ndx) {
var piece = Board[b][a].abs.truncate // get value corresponding to piece
ndx = -1
// call proper move listing routine depending on piece
if (piece == 100) {
ndx = pawn(a, b, xx, yy, ndx)
} else if (piece == 270) {
ndx = knight(a, b, xx, yy, ndx)
} else if (piece == 300) {
ndx = bishop(a, b, xx, yy, ndx)
} else if (piece == 500) {
ndx = rook(a, b, xx, yy, ndx)
} else if (piece == 900) {
ndx = queen(a, b, xx, yy, ndx)
} else {
ndx = king(a, b, xx, yy, ndx)
}
return ndx
}
// generate list of moves for pawn
static pawn(a, b, xx, yy, ndx) {
var id = Board[b][a].sign // get color
if (a - 1 >= 0 && a - 1 <= 7 && b - id >= 0 && b - id <= 7) {
// if there's a piece to capture, do so
if (Board[b-id][a-1].sign == -id) {
ndx = ndx + 1
xx[ndx] = a - 1
yy[ndx] = b - id
}
}
if (a + 1 >= 0 && a + 1 <= 7 && b - id >= 0 && b - id <= 7) {
if (Board[b-id][a+1].sign == -id) {
ndx = ndx + 1
xx[ndx] = a + 1
yy[ndx] = b - id
}
}
if (a >= 0 && a <= 7 && b - id >= 0 && b - id <= 7) {
// make sure square is empty
if (Board[b-id][a] == 0) {
ndx = ndx + 1
xx[ndx] = a
yy[ndx] = b - id
if ((id < 0 && b == 1) || (id > 0 && b == 6)) {
// if it's empty move two squares forward
if (Board[b-id-id][a] == 0) {
ndx = ndx + 1
xx[ndx] = a
yy[ndx] = b - 2*id
}
}
}
}
return ndx
}
// generate list of moves for queen
static queen(a, b, xx, yy, ndx) {
// queen's move = bishop + rook
ndx = bishop(a, b, xx, yy, ndx)
ndx = rook(a, b, xx, yy, ndx)
return ndx
}
// generate list of moves for rook
static rook(a, b, xx, yy, ndx) {
var id = Board[b][a].sign
// work out vert/horiz moves in each direction
for (x in Stepped.descend(a-1..0)) {
if (id != Board[b][x].sign) {
// if no piece of same color
ndx = ndx + 1
xx[ndx] = x
yy[ndx] = b
}
if (Board[b][x] != 0) break
}
for (x in Stepped.ascend(a+1..7)) {
if (id != Board[b][x].sign) {
ndx = ndx + 1
xx[ndx] = x
yy[ndx] = b
}
if (Board[b][x] != 0) break
}
for (y in Stepped.descend(b-1..0)) {
if (id != Board[y][a].sign) {
ndx = ndx + 1
xx[ndx] = a
yy[ndx] = y
}
if (Board[y][a] != 0) break
}
for (y in Stepped.ascend(b+1..7)) {
if (id != Board[y][a].sign) {
ndx = ndx + 1
xx[ndx] = a
yy[ndx] = y
}
if (Board[y][a] != 0) break
}
return ndx
}
// show board
static showbd() {
Terminal.locate(3, 30)
Color.set(7, 0)
System.print("A B C D E F G H")
for (k in 0..25) {
Terminal.locate(4, 28 + k)
Color.set(3, 0)
System.print(String.fromCodePoint(0x2584))
}
for (b in 0..7) {
Terminal.locate(2*b + 5, 26)
Color.set(7, 0)
System.print(String.fromCodePoint(56 - b))
Terminal.locate(2*b + 5, 28)
Color.set(3, 0)
System.print(String.fromCodePoint(0x2588))
Terminal.locate(2*b + 6, 28)
Color.set(3, 0)
System.print(String.fromCodePoint(0x2588))
for (a in 0..7) {
var colour = (((a + b) % 2) != 0) ? 8 : 9
square(3*a + 31, 2*b + 5, colour)
}
Terminal.locate(2*b + 5, 53)
Color.set(3, 0)
System.print(String.fromCodePoint(0x2588))
Terminal.locate(2*b + 6, 53)
Color.set(3, 0)
System.print(String.fromCodePoint(0x2588))
Terminal.locate(2*b + 6, 55)
Color.set(7, 0)
System.print(String.fromCodePoint(56 - b))
}
for (k in 0..25) {
Terminal.locate(21, 28 + k)
Color.set(3, 0)
System.print(String.fromCodePoint(0x2580))
}
Terminal.locate(22, 30)
Color.set(7, 0)
System.print("A B C D E F G H")
for (b in 0..7) {
for (a in 0..7) showman(a, b, 0)
}
Color.set(7, 0)
}
// show piece
static showman(a, b, flag) {
var back = (Board[b][a] <= 0) ? 0 : 7
var fore = 7 - back + flag
if (Board[b][a] == 0) {
back = (((a + b) & 1) != 0) ? 8 : 9
fore = back + (-1) * ((flag > 0) ? -1 : 0)
}
var piece = Board[b][a].abs.truncate
var n = (piece == 0) ? String.fromCodePoint(0x2588) :
(piece == 100) ? "P" :
(piece == 270) ? "N" :
(piece == 300) ? "B" :
(piece == 500) ? "R" :
(piece == 900) ? "Q" :
(piece == 5000) ? "K" :
(piece == 7500) ? "K" : " "
Terminal.locate(2*b + 5 - ((Board[b][a] > 0) ? -1 : 0), 3*a + 30)
Color.set(fore, back)
System.print(n)
Terminal.locate(1, 1)
Color.set(7, 0)
}
// display a square
static square(a, b, c) {
var mt = String.fromCodePoint(0x2588) * 3
Terminal.locate(b, a - 2)
Color.set(c, c)
System.print(mt)
Terminal.locate(b + 1, a - 2)
Color.set(c, c)
System.print(mt)
Color.set(7, 0)
}
// start a game
static start() {
var a = -1
var b = 0
var x = 8
var y = 8
var result = 0
while (true) {
Score = 0
io(a, b, x, y, result) // get white's move
if (End) {
Color.reset()
Terminal.clear()
return
}
Terminal.clear()
showbd() // update board to show white's move
result = evaluate(-1, 10000) // get black's move
a = BestA[1] // start column for black's move
b = BestB[1] // start row for black's move
x = BestX[1] // end column for black's move
y = BestY[1] // end row for black's move
}
}
}
Chess.start()