Switch to a legal move generator
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@ -122,7 +122,6 @@ func emptyPiece*: Piece {.inline.} = Piece(kind: Empty, color: None)
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func emptyLocation*: Location {.inline.} = (-1 , -1)
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func opposite*(c: PieceColor): PieceColor {.inline.} = (if c == White: Black else: White)
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proc algebraicToLocation*(s: string): Location {.inline.}
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func getCapture*(self: ChessBoard, move: Move): Location
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proc makeMove*(self: ChessBoard, startSquare, targetSquare: string): Move {.discardable.}
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proc makeMove*(self: ChessBoard, move: Move): Move {.discardable.}
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proc makeMove*(self: ChessBoard, startSquare, targetSquare: Location): Move {.discardable.}
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@ -130,11 +129,10 @@ func emptyMove*: Move {.inline.} = Move(startSquare: emptyLocation(), targetSqua
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func `+`*(a, b: Location): Location = (a.row + b.row, a.col + b.col)
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func isValid*(a: Location): bool {.inline.} = a.row in 0..7 and a.col in 0..7
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proc generateMoves(self: ChessBoard, location: Location): seq[Move]
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proc isAttacked*(self: ChessBoard, loc: Location): bool
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proc isAttacked*(self: ChessBoard, loc: Location, color: PieceColor = None): bool
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proc undoMove*(self: ChessBoard, move: Move)
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proc isLegal(self: ChessBoard, move: Move, keep: bool = false): bool
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proc isLegal(self: ChessBoard, move: Move): bool {.inline.}
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proc doMove(self: ChessBoard, move: Move)
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proc isLegalFast(self: ChessBoard, move: Move, keep: bool = false): bool
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proc pretty*(self: ChessBoard): string
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proc spawnPiece(self: ChessBoard, location: Location, piece: Piece)
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proc updateAttackedSquares(self: ChessBoard)
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@ -535,18 +533,16 @@ func getPiece*(self: ChessBoard, square: string): Piece =
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func isCapture*(self: ChessBoard, move: Move): bool {.inline.} =
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func isCapture*(move: Move): bool {.inline.} =
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## Returns whether the given move is a capture
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## or not
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return move.flag in [Capture, EnPassant]
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func getCapture*(self: ChessBoard, move: Move): Location =
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## Returns the location that would be captured if this
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## move were played on the board
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if not self.isCapture(move):
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return emptyLocation()
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return move.targetSquare
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func isPromotion*(move: Move): bool {.inline.} =
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## Returns whrther the given move is a
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## pawn promotion or not
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return move.flag in [PromoteToBishop, PromoteToKnight, PromoteToRook, PromoteToQueen]
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proc inCheck*(self: ChessBoard, color: PieceColor = None): bool =
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@ -559,9 +555,9 @@ proc inCheck*(self: ChessBoard, color: PieceColor = None): bool =
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color = self.getActiveColor()
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case color:
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of White:
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return self.isAttacked(self.position.pieces.white.king)
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return self.isAttacked(self.position.pieces.white.king, color)
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of Black:
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return self.isAttacked(self.position.pieces.black.king)
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return self.isAttacked(self.position.pieces.black.king, color)
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else:
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# Unreachable
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discard
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@ -586,65 +582,67 @@ proc canCastle*(self: ChessBoard, color: PieceColor = None): tuple[queen, king:
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of None:
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# Unreachable
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discard
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var
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loc: Location
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queenSide: Location
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kingSide: Location
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# If the path between the king and a rook is blocked, then castling
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# is prohibited on that side
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case color:
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of White:
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loc = self.position.pieces.white.king
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queenSide = color.leftSide()
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kingSide = color.rightSide()
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of Black:
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loc = self.position.pieces.black.king
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queenSide = color.rightSide()
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kingSide = color.leftSide()
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of None:
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# Unreachable
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discard
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if result.king or result.queen:
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var
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loc: Location
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queenSide: Location
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kingSide: Location
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if self.inCheck(color):
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# King can not castle out of check
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return (false, false)
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# If the path between the king and rook on a given side is blocked or any of the
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# squares where the king would travel to are attacked by the opponent,
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# then castling is (temporarily) prohibited on that side
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case color:
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of White:
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loc = self.position.pieces.white.king
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queenSide = color.leftSide()
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kingSide = color.rightSide()
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of Black:
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loc = self.position.pieces.black.king
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queenSide = color.rightSide()
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kingSide = color.leftSide()
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of None:
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# Unreachable
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discard
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if result.king:
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# Short castle
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var location = loc
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while true:
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location = location + kingSide
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if not location.isValid():
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break
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if self.grid[location.row, location.col].kind == Empty:
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continue
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if location == color.kingSideRook() and self.grid[location.row, location.col].kind == Rook:
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break
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# Blocked by a piece
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result.king = false
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break
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if result.queen:
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# Long castle
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var location = loc
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while true:
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location = location + queenSide
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if not location.isValid():
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break
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if self.grid[location.row, location.col].kind == Empty:
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continue
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if location == color.queenSideRook() and self.grid[location.row, location.col].kind == Rook:
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break
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# Blocked by a piece
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result.queen = false
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break
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# If the castling king would walk into, through or out of check
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# while castling on a given side, then it is not possible to castle
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# on that side until the threat exists
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if result.king:
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# Short castle
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var location = loc
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while true:
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location = location + kingSide
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if not location.isValid():
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break
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if self.grid[location.row, location.col].color == color:
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# Blocked by own piece
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result.king = false
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break
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# Square is attacked or blocked by enemy piece
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if self.isAttacked(location, color) or self.grid[location.row, location.col].color != None:
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result.king = false
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break
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# Square is occupied by our rook: we're done. No need to check the color or type of it (because
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# if it weren't the right color, castling rights would've already been lost and we wouldn't
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# have got this far)
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if location == color.kingSideRook():
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break
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# Square is empty and not attacked. Keep going
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if (result.king or result.queen) and self.inCheck(color):
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# Only check for checks if castling is still available
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# by this point (if we can avoid calls to generateMoves,
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# we should)
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return
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# TODO: Check for attacks in the various other squares
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if result.queen:
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# Long castle
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var location = loc
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while true:
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location = location + queenSide
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if not location.isValid():
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break
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if self.grid[location.row, location.col].color == color:
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result.queen = false
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break
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if self.isAttacked(location, color) or self.grid[location.row, location.col].color != None:
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result.queen = false
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break
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if location == color.queenSideRook():
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break
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proc generatePawnMoves(self: ChessBoard, location: Location): seq[Move] =
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@ -656,48 +654,46 @@ proc generatePawnMoves(self: ChessBoard, location: Location): seq[Move] =
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flags: seq[MoveFlag] = @[]
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doAssert piece.kind == Pawn, &"generatePawnMoves called on a {piece.kind}"
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# Pawns can move forward one square
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let forwardOffset = piece.color.forward()
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let forward = (forwardOffset + location)
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let forward = (piece.color.forward() + location)
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# Only if the square is empty though
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if forward.isValid() and self.grid[forward.row, forward.col].color == None:
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locations.add(forwardOffset)
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locations.add(forward)
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flags.add(Default)
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# If the pawn is on its first rank, it can push two squares
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if location.row == piece.getStartRow():
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let doubleOffset = piece.color.doublePush()
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let double = location + doubleOffset
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# Check if both squares are available
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let double = location + piece.color.doublePush()
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# Check that both squares are empty
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if double.isValid() and self.grid[forward.row, forward.col].color == None and self.grid[double.row, double.col].color == None:
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locations.add(piece.color.doublePush())
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locations.add(double)
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flags.add(DoublePush)
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# If the target is the en passant square and the piece under en passant
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# is of the opposite color of the pawn being moved, then we check if we
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# can do an en passant capture
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if self.position.enPassantSquare.piece.color == piece.color.opposite:
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if abs(self.position.enPassantSquare.targetSquare.col - location.col) == 1 and abs(self.position.enPassantSquare.targetSquare.row - location.row) == 1:
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# Only viable if the piece is on the diagonal of the target
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# Only viable if the piece is on the front diagonal of the target
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locations.add(self.position.enPassantSquare.targetSquare)
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flags.add(EnPassant)
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# They can also move on either diagonal one
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# square, but only to capture
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var diagonal = piece.color.topRightDiagonal()
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if (diagonal + location).isValid() and self.isCapture(Move(piece: piece, startSquare: location, targetSquare: location + diagonal)):
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var diagonal = location + piece.color.topRightDiagonal()
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if diagonal.isValid() and self.grid[diagonal.row, diagonal.col].color == piece.color.opposite() and self.grid[diagonal.row, diagonal.col].kind != King:
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locations.add(diagonal)
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flags.add(Capture)
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diagonal = piece.color.topLeftDiagonal()
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if (diagonal + location).isValid() and self.isCapture(Move(piece: piece, startSquare: location, targetSquare: location + diagonal)):
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diagonal = location + piece.color.topLeftDiagonal()
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if diagonal.isValid() and self.grid[diagonal.row, diagonal.col].color == piece.color.opposite() and self.grid[diagonal.row, diagonal.col].kind != King:
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locations.add(diagonal)
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flags.add(Capture)
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var
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newLocation: Location
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targetPiece: Piece
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var targetPiece: Piece
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for (target, flag) in zip(locations, flags):
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newLocation = location + target
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targetPiece = self.grid[newLocation.row, newLocation.col]
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if newLocation.row == piece.color.getLastRow():
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targetPiece = self.grid[target.row, target.col]
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if target.row == piece.color.getLastRow():
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# Pawn reached the other side of the board: generate all potential piece promotions
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for promotionType in [PromoteToKnight, PromoteToBishop, PromoteToRook, PromoteToQueen]:
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result.add(Move(startSquare: location, targetSquare: newLocation, piece: piece, flag: promotionType))
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result.add(Move(startSquare: location, targetSquare: target, piece: piece, flag: promotionType))
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continue
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result.add(Move(startSquare: location, targetSquare: newLocation, piece: piece, flag: flag))
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result.add(Move(startSquare: location, targetSquare: target, piece: piece, flag: flag))
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proc generateSlidingMoves(self: ChessBoard, location: Location): seq[Move] =
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@ -734,7 +730,9 @@ proc generateSlidingMoves(self: ChessBoard, location: Location): seq[Move] =
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if otherPiece.color == piece.color.opposite:
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# Target square contains an enemy piece: capture
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# it and stop going any further
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result.add(Move(startSquare: location, targetSquare: square, piece: piece, flag: Capture))
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if otherPiece.kind != King:
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# Can't capture the king
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result.add(Move(startSquare: location, targetSquare: square, piece: piece, flag: Capture))
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break
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# Target square is empty
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result.add(Move(startSquare: location, targetSquare: square, piece: piece))
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@ -754,30 +752,30 @@ proc generateKingMoves(self: ChessBoard, location: Location): seq[Move] =
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piece.color.leftSide(),
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piece.color.rightSide()]
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# Castling
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let canCastle = self.canCastle()
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let canCastle = self.canCastle(piece.color)
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if canCastle.queen:
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directions.add(longCastleKing())
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if canCastle.king:
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directions.add(shortCastleKing())
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var flag = Default
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for direction in directions:
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# Step in this direction once
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let square: Location = location + direction
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# End of board reached
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if not square.isValid():
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continue
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if direction == longCastleKing():
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flag = CastleLong
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elif direction == shortCastleKing():
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flag = CastleShort
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else:
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flag = Default
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# Step in this direction once
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let square: Location = location + direction
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# End of board reached
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if not square.isValid():
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continue
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let otherPiece = self.grid[square.row, square.col]
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if otherPiece.color == self.getActiveColor.opposite():
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flag = Capture
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# A friendly piece is in the way, move onto the next
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# direction
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if otherPiece.color == piece.color:
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# A friendly piece or the opponent king is in the way,
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# move onto the next direction
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if otherPiece.color == piece.color or otherPiece.kind == King:
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continue
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# Target square is empty or contains an enemy piece:
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# All good for us!
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@ -804,20 +802,20 @@ proc generateKnightMoves(self: ChessBoard, location: Location): seq[Move] =
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if not square.isValid():
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continue
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let otherPiece = self.grid[square.row, square.col]
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# A friendly piece is in the way
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if otherPiece.color == piece.color:
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# A friendly piece or the opponent king is is in the way
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if otherPiece.color == piece.color or otherPiece.kind == King:
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continue
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if otherPiece.color == piece.color.opposite:
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if otherPiece.color != None:
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# Target square contains an enemy piece: capture
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# it
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result.add(Move(startSquare: location, targetSquare: square, piece: piece, flag: Capture))
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continue
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# Target square is empty
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result.add(Move(startSquare: location, targetSquare: square, piece: piece))
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else:
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# Target square is empty
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result.add(Move(startSquare: location, targetSquare: square, piece: piece))
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proc generateMoves(self: ChessBoard, location: Location): seq[Move] =
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## Returns the list of possible pseudo-legal chess moves for the
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## Returns the list of possible legal chess moves for the
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## piece in the given location
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let piece = self.grid[location.row, location.col]
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case piece.kind:
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@ -834,7 +832,7 @@ proc generateMoves(self: ChessBoard, location: Location): seq[Move] =
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proc generateAllMoves*(self: ChessBoard): seq[Move] =
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## Returns the list of all possible pseudo-legal moves
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## Returns the list of all possible legal moves
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## in the current position
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for i, row in self.grid:
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for j, piece in row:
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@ -843,23 +841,36 @@ proc generateAllMoves*(self: ChessBoard): seq[Move] =
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result.add(move)
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proc getAttackers*(self: ChessBoard, square: Location): seq[Location] =
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proc getAttackers*(self: ChessBoard, square: Location, color = None): seq[Location] =
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## Returns all the attackers of the given square
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for attack in self.position.attacked.black:
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if attack.dest == square:
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result.add(attack.source)
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for attack in self.position.attacked.white:
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if attack.dest == square:
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result.add(attack.source)
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## for the given color (a color of None means use
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## the currently active color)
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var color = color
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if color == None:
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color = self.getActiveColor()
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case color:
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of White:
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for attack in self.position.attacked.black:
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if attack.dest == square:
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result.add(attack.source)
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of Black:
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for attack in self.position.attacked.white:
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if attack.dest == square:
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result.add(attack.source)
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else:
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# Unreachable
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discard
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# We don't use getAttackers because this one only cares about whether
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# the square is attacked or not (and can therefore exit earlier than
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# getAttackers)
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proc isAttacked*(self: ChessBoard, loc: Location): bool =
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proc isAttacked*(self: ChessBoard, loc: Location, color: PieceColor = None): bool =
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## Returns whether the given location is attacked
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## by the current opponent
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let piece = self.grid[loc.row, loc.col]
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case piece.color:
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## by the given opponent
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var color = color
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if color == None:
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color = self.getActiveColor()
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case color:
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of White:
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for attack in self.position.attacked.black:
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if attack.dest == loc:
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@ -869,17 +880,7 @@ proc isAttacked*(self: ChessBoard, loc: Location): bool =
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if attack.dest == loc:
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return true
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of None:
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case self.getActiveColor():
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of White:
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for attack in self.position.attacked.black:
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if attack.dest == loc:
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return true
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of Black:
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for attack in self.position.attacked.black:
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if attack.dest == loc:
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return true
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else:
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discard
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discard
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proc isAttacked*(self: ChessBoard, square: string): bool =
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@ -888,20 +889,66 @@ proc isAttacked*(self: ChessBoard, square: string): bool =
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return self.isAttacked(square.algebraicToLocation())
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func addAttack(self: ChessBoard, attack: tuple[source, dest: Location], color: PieceColor) {.inline.} =
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if attack.source.isValid() and attack.dest.isValid():
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case color:
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of White:
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self.position.attacked.white.add(attack)
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of Black:
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self.position.attacked.black.add(attack)
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else:
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discard
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proc updatePawnAttacks(self: ChessBoard) =
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## Internal helper of updateAttackedSquares
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for loc in self.position.pieces.white.pawns:
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# Pawns are special in how they capture (i.e. the
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# squares they can move to do not match the squares
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# they can capture on. Sneaky fucks)
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||||
let piece = self.grid[loc.row, loc.col]
|
||||
self.position.attacked.white.add((loc, loc + piece.color.topRightDiagonal()))
|
||||
self.position.attacked.white.add((loc, loc + piece.color.topLeftDiagonal()))
|
||||
self.addAttack((loc, loc + White.topRightDiagonal()), White)
|
||||
self.addAttack((loc, loc + White.topRightDiagonal()), White)
|
||||
# We do the same thing for black
|
||||
for loc in self.position.pieces.black.pawns:
|
||||
let piece = self.grid[loc.row, loc.col]
|
||||
self.position.attacked.black.add((loc, loc + piece.color.topRightDiagonal()))
|
||||
self.position.attacked.black.add((loc, loc + piece.color.topLeftDiagonal()))
|
||||
self.addAttack((loc, loc + Black.topRightDiagonal()), Black)
|
||||
self.addAttack((loc, loc + Black.topRightDiagonal()), Black)
|
||||
|
||||
|
||||
proc updateKingAttacks(self: ChessBoard) =
|
||||
## Internal helper of updateAttackedSquares
|
||||
var king = self.position.pieces.white.king
|
||||
self.addAttack((king, king + White.topRightDiagonal()), White)
|
||||
self.addAttack((king, king + White.topLeftDiagonal()), White)
|
||||
self.addAttack((king, king + White.bottomLeftDiagonal()), White)
|
||||
self.addAttack((king, king + White.bottomRightDiagonal()), White)
|
||||
king = self.position.pieces.black.king
|
||||
self.addAttack((king, king + Black.topRightDiagonal()), Black)
|
||||
self.addAttack((king, king + Black.topLeftDiagonal()), Black)
|
||||
self.addAttack((king, king + Black.bottomLeftDiagonal()), Black)
|
||||
self.addAttack((king, king + Black.bottomRightDiagonal()), Black)
|
||||
|
||||
|
||||
proc updateKnightAttacks(self: ChessBoard) =
|
||||
## Internal helper of updateAttackedSquares
|
||||
for loc in self.position.pieces.white.knights:
|
||||
self.addAttack((loc, loc + White.topLeftKnightMove()), White)
|
||||
self.addAttack((loc, loc + White.topRightKnightMove()), White)
|
||||
self.addAttack((loc, loc + White.bottomLeftKnightMove()), White)
|
||||
self.addAttack((loc, loc + White.bottomRightKnightMove()), White)
|
||||
self.addAttack((loc, loc + White.topLeftKnightMove(long=false)), White)
|
||||
self.addAttack((loc, loc + White.topRightKnightMove(long=false)), White)
|
||||
self.addAttack((loc, loc + White.bottomLeftKnightMove(long=false)), White)
|
||||
self.addAttack((loc, loc + White.bottomRightKnightMove(long=false)), White)
|
||||
|
||||
for loc in self.position.pieces.black.knights:
|
||||
self.addAttack((loc, loc + Black.topLeftKnightMove()), Black)
|
||||
self.addAttack((loc, loc + Black.topRightKnightMove()), Black)
|
||||
self.addAttack((loc, loc + Black.bottomLeftKnightMove()), Black)
|
||||
self.addAttack((loc, loc + Black.bottomRightKnightMove()), Black)
|
||||
self.addAttack((loc, loc + Black.topLeftKnightMove(long=false)), Black)
|
||||
self.addAttack((loc, loc + Black.topRightKnightMove(long=false)), Black)
|
||||
self.addAttack((loc, loc + Black.bottomLeftKnightMove(long=false)), Black)
|
||||
self.addAttack((loc, loc + Black.bottomRightKnightMove(long=false)), Black)
|
||||
|
||||
|
||||
proc getSlidingAttacks(self: ChessBoard, loc: Location): Attacked =
|
||||
|
|
@ -947,24 +994,24 @@ proc updateSlidingAttacks(self: ChessBoard) =
|
|||
# Bishops
|
||||
for loc in self.position.pieces.white.bishops:
|
||||
for attack in self.getSlidingAttacks(loc):
|
||||
self.position.attacked.white.add(attack)
|
||||
self.addAttack(attack, White)
|
||||
for loc in self.position.pieces.black.bishops:
|
||||
for attack in self.getSlidingAttacks(loc):
|
||||
self.position.attacked.black.add(attack)
|
||||
self.addAttack(attack, Black)
|
||||
# Rooks
|
||||
for loc in self.position.pieces.white.rooks:
|
||||
for attack in self.getSlidingAttacks(loc):
|
||||
self.position.attacked.white.add(attack)
|
||||
self.addAttack(attack, White)
|
||||
for loc in self.position.pieces.black.rooks:
|
||||
for attack in self.getSlidingAttacks(loc):
|
||||
self.position.attacked.black.add(attack)
|
||||
self.addAttack(attack, Black)
|
||||
# Queens
|
||||
for loc in self.position.pieces.white.queens:
|
||||
for attack in self.getSlidingAttacks(loc):
|
||||
self.position.attacked.white.add(attack)
|
||||
self.addAttack(attack, White)
|
||||
for loc in self.position.pieces.black.queens:
|
||||
for attack in self.getSlidingAttacks(loc):
|
||||
self.position.attacked.black.add(attack)
|
||||
self.addAttack(attack, Black)
|
||||
|
||||
|
||||
proc updateAttackedSquares(self: ChessBoard) =
|
||||
|
|
@ -977,28 +1024,16 @@ proc updateAttackedSquares(self: ChessBoard) =
|
|||
self.updatePawnAttacks()
|
||||
# Sliding pieces
|
||||
self.updateSlidingAttacks()
|
||||
# Knights
|
||||
for loc in self.position.pieces.white.knights:
|
||||
for move in self.generateMoves(loc):
|
||||
self.position.attacked.white.add((move.startSquare, move.targetSquare))
|
||||
# King
|
||||
for move in self.generateMoves(self.position.pieces.white.king):
|
||||
self.position.attacked.white.add((move.startSquare, move.targetSquare))
|
||||
# Knights
|
||||
for loc in self.position.pieces.black.knights:
|
||||
for move in self.generateMoves(loc):
|
||||
self.position.attacked.black.add((move.startSquare, move.targetSquare))
|
||||
# King
|
||||
for move in self.generateMoves(self.position.pieces.black.king):
|
||||
self.position.attacked.black.add((move.startSquare, move.targetSquare))
|
||||
self.updateKnightAttacks()
|
||||
# Kings
|
||||
self.updateKingAttacks()
|
||||
|
||||
|
||||
proc removePiece(self: ChessBoard, location: Location, emptyGrid: bool = true) =
|
||||
proc removePiece(self: ChessBoard, location: Location, attack: bool = true) =
|
||||
## Removes a piece from the board, updating necessary
|
||||
## metadata
|
||||
var piece = self.grid[location.row, location.col]
|
||||
if emptyGrid:
|
||||
self.grid[location.row, location.col] = emptyPiece()
|
||||
self.grid[location.row, location.col] = emptyPiece()
|
||||
case piece.color:
|
||||
of White:
|
||||
case piece.kind:
|
||||
|
|
@ -1034,6 +1069,8 @@ proc removePiece(self: ChessBoard, location: Location, emptyGrid: bool = true) =
|
|||
discard
|
||||
else:
|
||||
discard
|
||||
if attack:
|
||||
self.updateAttackedSquares()
|
||||
|
||||
|
||||
proc movePiece(self: ChessBoard, move: Move, attack: bool = true) =
|
||||
|
|
@ -1108,10 +1145,14 @@ proc movePiece(self: ChessBoard, startSquare, targetSquare: Location, attack: bo
|
|||
proc updateLocations(self: ChessBoard, move: Move) =
|
||||
## Internal helper to update the position of
|
||||
## the pieces on the board after a move
|
||||
let capture = self.getCapture(move)
|
||||
if capture != emptyLocation():
|
||||
self.position.captured = self.grid[capture.row, capture.col]
|
||||
self.removePiece(capture)
|
||||
if move.isCapture():
|
||||
self.position.captured = self.grid[move.targetSquare.row, move.targetSquare.col]
|
||||
try:
|
||||
self.removePiece(move.targetSquare, attack=false)
|
||||
except AssertionDefect:
|
||||
echo move
|
||||
raise
|
||||
|
||||
# Update the positional metadata of the moving piece
|
||||
self.movePiece(move)
|
||||
|
||||
|
|
@ -1132,8 +1173,7 @@ proc doMove(self: ChessBoard, move: Move) =
|
|||
halfMoveClock = self.position.halfMoveClock
|
||||
fullMoveCount = self.position.fullMoveCount
|
||||
castlingAvailable = self.position.castlingAvailable
|
||||
let capture = self.getCapture(move)
|
||||
if move.piece.kind == Pawn or self.isCapture(move):
|
||||
if move.piece.kind == Pawn or move.isCapture():
|
||||
halfMoveClock = 0
|
||||
else:
|
||||
inc(halfMoveClock)
|
||||
|
|
@ -1161,22 +1201,22 @@ proc doMove(self: ChessBoard, move: Move) =
|
|||
else:
|
||||
discard
|
||||
# Has a rook been captured?
|
||||
if capture != emptyLocation():
|
||||
let piece = self.grid[capture.row, capture.col]
|
||||
if move.isCapture():
|
||||
let piece = self.grid[move.targetSquare.row, move.targetSquare.col]
|
||||
if piece.kind == Rook:
|
||||
case piece.color:
|
||||
of White:
|
||||
if capture == piece.color.queenSideRook():
|
||||
if move.targetSquare == piece.color.queenSideRook():
|
||||
# Queen side
|
||||
castlingAvailable.white.queen = false
|
||||
elif capture == piece.color.kingSideRook():
|
||||
elif move.targetSquare == piece.color.kingSideRook():
|
||||
# King side
|
||||
castlingAvailable.white.king = false
|
||||
of Black:
|
||||
if capture == piece.color.queenSideRook():
|
||||
if move.targetSquare == piece.color.queenSideRook():
|
||||
# Queen side
|
||||
castlingAvailable.black.queen = false
|
||||
elif capture == piece.color.kingSideRook():
|
||||
elif move.targetSquare == piece.color.kingSideRook():
|
||||
# King side
|
||||
castlingAvailable.black.king = false
|
||||
else:
|
||||
|
|
@ -1193,7 +1233,22 @@ proc doMove(self: ChessBoard, move: Move) =
|
|||
castlingAvailable.black.queen = false
|
||||
else:
|
||||
discard
|
||||
|
||||
if move.isPromotion():
|
||||
# Move is a pawn promotion: get rid of then pawn
|
||||
# and spawn a new piece
|
||||
self.removePiece(move.startSquare)
|
||||
case move.flag:
|
||||
of PromoteToBishop:
|
||||
self.spawnPiece(move.targetSquare, Piece(kind: Bishop, color: move.piece.color))
|
||||
of PromoteToKnight:
|
||||
self.spawnPiece(move.targetSquare, Piece(kind: Knight, color: move.piece.color))
|
||||
of PromoteToRook:
|
||||
self.spawnPiece(move.targetSquare, Piece(kind: Rook, color: move.piece.color))
|
||||
of PromoteToQueen:
|
||||
self.spawnPiece(move.targetSquare, Piece(kind: Queen, color: move.piece.color))
|
||||
|
||||
else:
|
||||
discard
|
||||
let previous = self.position
|
||||
# Record final position for future reference
|
||||
self.positions.add(previous)
|
||||
|
|
@ -1211,6 +1266,16 @@ proc doMove(self: ChessBoard, move: Move) =
|
|||
|
||||
var location: Location
|
||||
if move.flag in [CastleShort, CastleLong]:
|
||||
# Revoke all castling rights for the moving king
|
||||
case move.piece.color:
|
||||
of White:
|
||||
self.position.castlingAvailable.white.king = false
|
||||
self.position.castlingAvailable.white.queen = false
|
||||
of Black:
|
||||
self.position.castlingAvailable.black.king = false
|
||||
self.position.castlingAvailable.black.queen = false
|
||||
else:
|
||||
discard
|
||||
# Move the rook onto the
|
||||
# correct file
|
||||
var
|
||||
|
|
@ -1283,63 +1348,82 @@ proc spawnPiece(self: ChessBoard, location: Location, piece: Piece) =
|
|||
self.grid[location.row, location.col] = piece
|
||||
|
||||
|
||||
proc resetBoard*(self: ChessBoard) =
|
||||
## Resets the internal grid representation
|
||||
## according to the positional data stored
|
||||
## in the chessboard. Warning: this can be
|
||||
## expensive, especially in critical paths
|
||||
## or tight loops
|
||||
self.grid = newMatrixFromSeq[Piece](empty, (8, 8))
|
||||
for loc in self.position.pieces.white.pawns:
|
||||
self.grid[loc.row, loc.col] = Piece(color: White, kind: Pawn)
|
||||
for loc in self.position.pieces.black.pawns:
|
||||
self.grid[loc.row, loc.col] = Piece(color: Black, kind: Pawn)
|
||||
for loc in self.position.pieces.white.bishops:
|
||||
self.grid[loc.row, loc.col] = Piece(color: White, kind: Bishop)
|
||||
for loc in self.position.pieces.black.bishops:
|
||||
self.grid[loc.row, loc.col] = Piece(color: Black, kind: Bishop)
|
||||
for loc in self.position.pieces.white.knights:
|
||||
self.grid[loc.row, loc.col] = Piece(color: White, kind: Knight)
|
||||
for loc in self.position.pieces.black.knights:
|
||||
self.grid[loc.row, loc.col] = Piece(color: Black, kind: Knight)
|
||||
for loc in self.position.pieces.white.rooks:
|
||||
self.grid[loc.row, loc.col] = Piece(color: White, kind: Rook)
|
||||
for loc in self.position.pieces.black.rooks:
|
||||
self.grid[loc.row, loc.col] = Piece(color: Black, kind: Rook)
|
||||
for loc in self.position.pieces.white.queens:
|
||||
self.grid[loc.row, loc.col] = Piece(color: White, kind: Queen)
|
||||
for loc in self.position.pieces.black.queens:
|
||||
self.grid[loc.row, loc.col] = Piece(color: Black, kind: Queen)
|
||||
self.grid[self.position.pieces.white.king.row, self.position.pieces.white.king.col] = Piece(color: White, kind: King)
|
||||
self.grid[self.position.pieces.black.king.row, self.position.pieces.black.king.col] = Piece(color: Black, kind: King)
|
||||
|
||||
|
||||
proc undoMove*(self: ChessBoard, move: Move) =
|
||||
## Undoes the given move
|
||||
if self.positions.len() == 0:
|
||||
return
|
||||
let previous = self.position
|
||||
var position = self.positions[^1]
|
||||
while true:
|
||||
if position.move == move:
|
||||
break
|
||||
while position.move != move:
|
||||
discard self.positions.pop()
|
||||
position = self.positions[^1]
|
||||
|
||||
self.position = position
|
||||
self.grid[move.startSquare.row, move.startSquare.col] = move.piece
|
||||
if self.isCapture(move):
|
||||
self.grid[move.targetSquare.row, move.targetSquare.col] = self.position.captured
|
||||
if move.isCapture():
|
||||
self.grid[move.targetSquare.row, move.targetSquare.col] = previous.captured
|
||||
else:
|
||||
self.grid[move.targetSquare.row, move.targetSquare.col] = emptyPiece()
|
||||
self.position = position
|
||||
# Reset the location of the rook in the
|
||||
# grid (it's already correct in the piece
|
||||
# list)
|
||||
if move.flag == CastleLong:
|
||||
let
|
||||
rookOld = move.targetSquare + move.piece.color.rightSide()
|
||||
rookNew = move.piece.color.queenSideRook()
|
||||
self.grid[rookNew.row, rookNew.col] = self.grid[rookOld.row, rookOld.col]
|
||||
self.grid[rookOld.row, rookOld.col] = emptyPiece()
|
||||
if move.flag == CastleShort:
|
||||
let
|
||||
rookOld = move.targetSquare + move.piece.color.leftSide()
|
||||
rookNew = move.piece.color.kingSideRook()
|
||||
self.grid[rookNew.row, rookNew.col] = self.grid[rookOld.row, rookOld.col]
|
||||
self.grid[rookOld.row, rookOld.col] = emptyPiece()
|
||||
|
||||
|
||||
|
||||
proc isLegal(self: ChessBoard, move: Move, keep: bool = false): bool =
|
||||
proc isLegal(self: ChessBoard, move: Move): bool {.inline.} =
|
||||
## Returns whether the given move is legal
|
||||
self.doMove(move)
|
||||
if move notin self.generateMoves(move.startSquare):
|
||||
# Piece cannot arrive to destination (blocked
|
||||
# or otherwise invalid move)
|
||||
return false
|
||||
if not keep:
|
||||
defer: self.undoMove(move)
|
||||
# Move would reveal an attack
|
||||
# on our king: not allowed
|
||||
return self.inCheck(move.piece.color)
|
||||
|
||||
|
||||
proc isLegalFast(self: ChessBoard, move: Move, keep: bool = false): bool =
|
||||
## Returns whether the given move is legal
|
||||
## assuming that the input move is pseudo legal
|
||||
self.position.move = move
|
||||
self.doMove(move)
|
||||
if not keep:
|
||||
defer: self.undoMove(move)
|
||||
|
||||
# Move would reveal an attack
|
||||
# on our king: not allowed
|
||||
if self.inCheck(move.piece.color):
|
||||
return false
|
||||
# All checks have passed: move is legal
|
||||
result = true
|
||||
return move in self.generateMoves(move.startSquare)
|
||||
|
||||
|
||||
proc makeMove*(self: ChessBoard, move: Move): Move {.discardable.} =
|
||||
## Like the other makeMove(), but with a Move object
|
||||
result = move
|
||||
self.position.move = move
|
||||
let legal = self.isLegal(move, keep=true)
|
||||
if not legal:
|
||||
if not self.isLegal(move):
|
||||
return emptyMove()
|
||||
self.doMove(move)
|
||||
result = self.position.move
|
||||
|
||||
|
||||
|
|
@ -1409,37 +1493,59 @@ proc pretty*(self: ChessBoard): string =
|
|||
result &= "\x1b[0m"
|
||||
|
||||
|
||||
proc countLegalMoves*(self: ChessBoard, ply: int, verbose: bool = false, current: int = 0): int =
|
||||
proc countLegalMoves*(self: ChessBoard, ply: int, verbose: bool = false, current: int = 0): tuple[nodes: int, captures: int, castles: int, checks: int, promotions: int] =
|
||||
## Counts (and debugs) the number of legal positions reached after
|
||||
## the given number of half moves
|
||||
## the given number of ply
|
||||
if ply == 0:
|
||||
result = 1
|
||||
result = (1, 0, 0, 0, 0)
|
||||
else:
|
||||
var before: string
|
||||
var
|
||||
before: string
|
||||
for move in self.generateAllMoves():
|
||||
before = self.pretty()
|
||||
self.doMove(move)
|
||||
if not self.inCheck(move.piece.color):
|
||||
if verbose:
|
||||
let canCastle = self.canCastle()
|
||||
echo "\x1Bc"
|
||||
echo &"Ply: {self.position.plyFromRoot} (move {current + result + 1})"
|
||||
echo &"Move: {move.startSquare.locationToAlgebraic()}{move.targetSquare.locationToAlgebraic()} (({move.startSquare.row}, {move.startSquare.col}) -> ({move.targetSquare.row}, {move.targetSquare.col}))"
|
||||
echo &"Turn: {move.piece.color}"
|
||||
echo &"Piece: {move.piece.kind}"
|
||||
echo &"Flag: {move.flag}"
|
||||
echo &"Can castle:\n - King side: {(if canCastle.king: \"yes\" else: \"no\")}\n - Queen side: {(if canCastle.queen: \"yes\" else: \"no\")}"
|
||||
echo "\nBefore:"
|
||||
echo before
|
||||
echo "\nNow: "
|
||||
echo self.pretty()
|
||||
try:
|
||||
discard readLine(stdin)
|
||||
except IOError:
|
||||
discard
|
||||
except EOFError:
|
||||
discard
|
||||
result += self.countLegalMoves(ply - 1, verbose, result + 1)
|
||||
case move.flag:
|
||||
of Capture:
|
||||
inc(result.captures)
|
||||
of CastleShort, CastleLong:
|
||||
inc(result.castles)
|
||||
of PromoteToBishop, PromoteToKnight, PromoteToQueen, PromoteToRook:
|
||||
inc(result.promotions)
|
||||
else:
|
||||
discard
|
||||
if self.inCheck():
|
||||
# Opponent king is in check
|
||||
inc(result.checks)
|
||||
if verbose:
|
||||
let canCastle = self.canCastle(move.piece.color)
|
||||
echo "\x1Bc"
|
||||
echo &"Ply: {self.position.plyFromRoot} (move {current + result.nodes + 1})"
|
||||
echo &"Move: {move.startSquare.locationToAlgebraic()}{move.targetSquare.locationToAlgebraic()} (({move.startSquare.row}, {move.startSquare.col}) -> ({move.targetSquare.row}, {move.targetSquare.col}))"
|
||||
echo &"Turn: {move.piece.color}"
|
||||
echo &"Piece: {move.piece.kind}"
|
||||
echo &"Flag: {move.flag}"
|
||||
echo &"Can castle:\n - King side: {(if canCastle.king: \"yes\" else: \"no\")}\n - Queen side: {(if canCastle.queen: \"yes\" else: \"no\")}"
|
||||
echo "\nBefore:"
|
||||
echo before
|
||||
echo "\nNow: "
|
||||
echo self.pretty()
|
||||
echo &"\n\nTotal captures: {result.captures}"
|
||||
echo &"Total castles: {result.castles}"
|
||||
echo &"Total checks: {result.checks}"
|
||||
echo &"Total promotions: {result.promotions}"
|
||||
|
||||
try:
|
||||
discard readLine(stdin)
|
||||
except IOError:
|
||||
discard
|
||||
except EOFError:
|
||||
discard
|
||||
let next = self.countLegalMoves(ply - 1, verbose, result.nodes + 1)
|
||||
result.nodes += next.nodes
|
||||
result.captures += next.captures
|
||||
result.checks += next.checks
|
||||
result.promotions += next.promotions
|
||||
result.castles += next.castles
|
||||
self.undoMove(move)
|
||||
|
||||
|
||||
|
|
@ -1501,6 +1607,6 @@ when isMainModule:
|
|||
when compileOption("profiler"):
|
||||
import nimprof
|
||||
|
||||
|
||||
echo b.countLegalMoves(4, verbose=false)
|
||||
#b = newChessboardFromFEN("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ")
|
||||
echo b.countLegalMoves(3, verbose=false)
|
||||
echo "All tests were successful"
|
||||
Loading…
Reference in New Issue