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chess: refactoring genDests
genDests procs where copy and pasted, now they are done by a common function. Single line functions where also removed, due to them being to trivial
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TiynGER
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131
src/chess.nim
131
src/chess.nim
@ -39,41 +39,41 @@ type
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Pieces = array[10, int]
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const
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Block = 999 ## \
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Block = 999 ## \
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## `Block` is the value assigned to empty blocked fields in a board.
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WPawn* = 1
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## `WPawn` is the value assigned to a square in a board with a white pawn.
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WKnight* = 2 ## \
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WKnight* = 2 ## \
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## `WKnight` is the value assigned to a square in a board with a white
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## knight.
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WBishop* = 3 ## \
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WBishop* = 3 ## \
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## `WBishop` is the value assigned to a square in a board with a white
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## bishop.
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WRook* = 4 ## \
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WRook* = 4 ## \
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## `WRook` is the value assigned to a square in a board with a white rook.
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WQueen* = 5 ## \
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WQueen* = 5 ## \
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## `WQueen` is the value assigned to a square in a board with a white
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## queen.
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WKing* = 6 ## \
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WKing* = 6 ## \
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## `WKing` is the value assigned to a square in a board with a white king.
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WEnPassant = 7 ## \
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WEnPassant = 7 ## \
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## `WEnPassant` is assigned to a square in a board with an invisible white
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## en passant pawn.
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BPawn* = -WPawn ## \
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BPawn* = -WPawn ## \
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## `BPawn` is the value assigned to a square in a board with a black pawn.
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BKnight* = -WKnight ## \
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BKnight* = -WKnight ## \
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## `BKnight` is the value assigned to a square in a board with a black\
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## knight.
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BBishop* = -WBishop ## \
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BBishop* = -WBishop ## \
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## `BBishop` is the value assigned to a square in a board with a black\
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## bishop.
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BRook* = -WRook ## \
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BRook* = -WRook ## \
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## `BRook` is the value assigned to a square in a board with a black rook.
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BQueen* = -WQueen ## \
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BQueen* = -WQueen ## \
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## `BQueen` is the value assigned to a square in a board with a black queen.
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BKing* = -WKing ## \
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BKing* = -WKing ## \
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## `BKing` is the value assigned to a square in a board with a black king.
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BEnPassant = -WEnPassant ## \
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BEnPassant = -WEnPassant ## \
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## `BEnPassant` is assigned to a square in a board with an invisible black
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## en passant pawn.
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N = 10 ## `N` describes a move a field up the board from whites perspective.
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@ -81,34 +81,34 @@ const
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E = 1 ## `E` describes a move a field to the right from whites perspective.
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W = -E ## `W` describes a move a field to the left from whites perspective.
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# Directions for the pieces. Special moves are in separate arrays.
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Knight_Moves = [N+N+E, N+N+W, E+E+N, E+E+S, S+S+E, S+S+W, W+W+N, W+W+S] ## \
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Knight_Moves = @[N+N+E, N+N+W, E+E+N, E+E+S, S+S+E, S+S+W, W+W+N, W+W+S] ## \
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## `Knight_Moves` describes the possible knight moves.
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Bishop_Moves = [N+E, N+W, S+E, S+W] ## \
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Bishop_Moves = @[N+E, N+W, S+E, S+W] ## \
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## `Bishop_Moves` describes the possible 1 field distance bishop moves.
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Rook_Moves = [N, E, S, W] ## \
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Rook_Moves = @[N, E, S, W] ## \
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## `Rook_Moves` describes the possible 1 field distance rook moves.
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Queen_Moves = [N, E, S, W, N+E, N+W, S+E, S+W] ## \
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Queen_Moves = @[N, E, S, W, N+E, N+W, S+E, S+W] ## \
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## `Queen_Moves` describes the possible 1 field distance queen moves.
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King_Moves = [N, E, S, W, N+E, N+W, S+E, S+W] ## \
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King_Moves = @[N, E, S, W, N+E, N+W, S+E, S+W] ## \
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## `King_Moves` describes the possible 1 field distance king moves.
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King_Moves_White_Castle = [E+E, W+W] ## \
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King_Moves_White_Castle = @[E+E, W+W] ## \
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## `King_Moves` describes the possible king moves for castling.
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Pawn_Moves_White = [N] ## \
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Pawn_Moves_White = @[N] ## \
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## `Pawn_Moves_White` describes the possible 1 field distance pawn moves
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## from whites perspective that are not attacks.
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Pawn_Moves_White_Double = [N+N] ## \
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Pawn_Moves_White_Double = @[N+N] ## \
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## `Pawn_Moves_White_Double` describes the possible pawn 2 field distance
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## moves from whites perspective.
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Pawn_Moves_White_Attack = [N+E, N+W] ## \
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Pawn_Moves_White_Attack = @[N+E, N+W] ## \
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## `Pawn_Moves_White` describes the possible 1 field distance pawn moves
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## from whites perspective that are ttacks.
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InsufficientMaterial: array[4, PieceAmount] = [
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(0, 0, 0, 0, 0), # only kings
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(0, 0, 1, 0, 0), # bishop only
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(0, 1, 0, 0, 0), # knight only
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(0, 2, 0, 0, 0) # 2 knights
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(0, 0, 0, 0, 0), # only kings
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(0, 0, 1, 0, 0), # bishop only
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(0, 1, 0, 0, 0), # knight only
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(0, 2, 0, 0, 0) # 2 knights
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] ## `InsufficientMaterial` describes the pieces where no checkmate can be
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## forced
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## forced
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let
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PieceChar = {
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@ -264,7 +264,6 @@ proc initChess(board: array[0..63, int], color: Color): Chess =
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## `board` describes the pieces, `color` the color that is about to move.
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let board = initBoard(board)
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let compare = initBoard()
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var same_piece: bool
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var wk: bool
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var wq: bool
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var bk: bool
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@ -279,8 +278,6 @@ proc initChess(board: array[0..63, int], color: Color): Chess =
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bq = true
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if (board[fieldToInd("h8")] == compare[fieldToInd("h8")]):
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bk = true
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for ind in board.low..board.high:
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same_piece = (board[ind] != compare[ind])
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let chess = Chess(board: board,
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to_move: color, castleRights: (wk, wq, bk, bq))
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return chess
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@ -288,7 +285,7 @@ proc initChess(board: array[0..63, int], color: Color): Chess =
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proc echoBoard*(chess: Chess, color: Color) =
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## Prints out the given `board` with its pieces as characters and line
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## indices from perspecive of `color`.
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var line_str = ""
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var line_str: string
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if (color == Color.Black):
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for i in 0..len(chess.board)-1:
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if (chess.board[i] == Block):
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@ -299,7 +296,7 @@ proc echoBoard*(chess: Chess, color: Color) =
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echo line_str
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echo "h g f e d c b a"
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else:
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for i in len(chess.board)-1..0:
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for i in countdown(len(chess.board)-1, 0):
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if (chess.board[i] == Block):
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continue
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line_str &= PieceChar[chess.board[i]] & " "
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@ -338,8 +335,6 @@ proc genPawnDoubleDests(chess: Chess, field: int, color: Color): seq[int] =
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var target: int
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for doubles in Pawn_Moves_White_Double:
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dest = field + doubles * ord(color)
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if (not dest in chess.board.low..chess.board.high):
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continue
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target = chess.board[dest]
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if ((target != 0) or (
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chess.board[dest + (S * ord(color))] != 0)):
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@ -391,16 +386,16 @@ proc genKnightDests(chess: Chess, field: int, color: Color): seq[int] =
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res.add(dest)
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return res
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proc genBishopDests(chess: Chess, field: int, color: Color): seq[int] =
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## Generate possible destinations for a bishop with specific `color` located
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## at index `field` of `chess`.
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proc genSlidePieceDests(chess: Chess, field: int, color: Color, moves: seq[int]): seq[int] =
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## Generate possible destinations for a piece with `moves` and specific `color`
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## located at index `field` of `chess`.
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## Returns a sequence of possible indices to move to.
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if (not field in chess.board.low..chess.board.high):
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return @[]
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var res = newSeq[int]()
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var dest: int
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var target: int
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for move in Bishop_Moves:
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for move in moves:
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dest = field + move
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if (not dest in chess.board.low..chess.board.high):
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continue
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@ -414,51 +409,23 @@ proc genBishopDests(chess: Chess, field: int, color: Color): seq[int] =
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target = chess.board[dest]
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return res
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proc genBishopDests(chess: Chess, field: int, color: Color): seq[int] =
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## Generate possible destinations for a bishop with specific `color` located
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## at index `field` of `chess`.
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## Returns a sequence of possible indices to move to.
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return genSlidePieceDests(chess, field, color, Bishop_Moves)
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proc genRookDests(chess: Chess, field: int, color: Color): seq[int] =
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## Generate possible destinations for a rook with specific `color` located at
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## index `field` of `chess`.
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## Returns a sequence of possible indices to move to.
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if (not field in chess.board.low..chess.board.high):
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return @[]
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var res = newSeq[int]()
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var dest: int
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var target: int
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for move in Rook_Moves:
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dest = field + move
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if (not dest in chess.board.low..chess.board.high):
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continue
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target = chess.board[dest]
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while (target != Block and (ord(color) * target <= 0) or abs(target) ==
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WEnPassant):
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res.add(dest)
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if (ord(color) * target < 0 and ord(color) * target > BEnPassant):
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break
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dest = dest + move
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target = chess.board[dest]
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return res
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return genSlidePieceDests(chess, field, color, Rook_Moves)
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proc genQueenDests(chess: Chess, field: int, color: Color): seq[int] =
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## Generate possible destinations for a queen with specific `color` located
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## at index `field` of `chess`.
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## Returns a sequence of possible indices to move to.
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if (not field in chess.board.low..chess.board.high):
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return @[]
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var res = newSeq[int]()
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var dest: int
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var target: int
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for move in Queen_Moves:
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dest = field + move
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if (not dest in chess.board.low..chess.board.high):
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continue
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target = chess.board[dest]
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while (target != Block and (ord(color) * target <= 0) or abs(target) ==
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WEnPassant):
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res.add(dest)
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if (ord(color) * target < 0 and ord(color) * target > BEnPassant):
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break
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dest = dest + move
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target = chess.board[dest]
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return res
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return genSlidePieceDests(chess, field, color, Queen_Moves)
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proc genKingCastleDest(chess: Chess, field: int, color: Color): seq[int] =
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## Generate possible castle destinations for a king with specific `color`
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@ -791,13 +758,9 @@ proc checkedMove*(chess: var Chess, move: Move): bool {.discardable.} =
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chess.fiftyMoveCounter = 0
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return true
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proc hasNoMoves(chess: Chess, color: Color): bool =
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## Returns true if the `color` player has no legal moves in a `chess`.
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return (chess.genLegalMoves(color) == @[])
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proc isCheckmate*(chess: Chess, color: Color): bool =
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## Returns true if the `color` player is checkmate in a `chess`.
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return chess.hasNoMoves(color) and chess.isInCheck(color)
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return chess.genLegalMoves(color) == @[] and chess.isInCheck(color)
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proc threeMoveRep(chess: Chess): bool =
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## Returns true if a 3-fold repitition happened on the last move of the
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@ -813,13 +776,9 @@ proc threeMoveRep(chess: Chess): bool =
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reps = reps + 1
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return reps >= 3
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proc fiftyMoveRule(chess: Chess): bool =
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## Returns true if a draw can be claimed by the 50 move rule in a `chess`.
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return chess.fiftyMoveCounter >= 100
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proc isDrawClaimable*(chess: Chess): bool =
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## Returns true if a draw is claimable by either player.
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return chess.threeMoveRep() or chess.fiftyMoveRule()
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return chess.threeMoveRep() or chess.fiftyMoveCounter >= 100
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proc checkInsufficientMaterial(board: Board): bool =
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## Checks for combinations of pieces on a `board`, where no checkmate can be
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@ -843,5 +802,5 @@ proc checkInsufficientMaterial(board: Board): bool =
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proc isStalemate*(chess: Chess, color: Color): bool =
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## Returns true if the `color` player is stalemate in a `chess`.
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return (chess.hasNoMoves(color) and not chess.isInCheck(color)) or
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return (chess.genLegalMoves(color) == @[] and not chess.isInCheck(color)) or
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chess.board.checkInsufficientMaterial()
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