Fix algebraicToLocation and added getPiece function
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@ -13,12 +13,17 @@
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# limitations under the License.
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import ../util/matrix
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export matrix
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import std/strutils
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import std/strformat
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type
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Location = tuple[row, col: int]
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Pieces = tuple[king: Location, queen: Location, rooks: array[2, Location],
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bishops: array[2, Location], knights: array[2, Location],
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pawns: array[8, Location]]
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PieceColor* = enum
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None = 0,
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White,
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@ -36,10 +41,10 @@ type
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kind*: PieceKind
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Position* = object
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piece*: Piece
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location*: tuple[row, col: int]
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location*: Location
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ChessBoard* = ref object
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## A chess board object
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grid: Matrix[Piece]
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grid*: Matrix[Piece]
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# Currently active color
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turn: PieceColor
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# Number of half moves since
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@ -55,6 +60,11 @@ type
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# If en passant is not possible, both the row and
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# column of the position will be set to -1
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enPassantSquare: Position
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# Locations of all pieces
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pieces: tuple[white: Pieces, black: Pieces]
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# Locations of all attacked squares
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attacked: tuple[white: seq[Location], black: seq[Location]]
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# Initialized only once, copied every time
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var empty: seq[Piece] = @[]
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@ -62,12 +72,46 @@ for _ in countup(0, 63):
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empty.add(Piece(kind: Empty, color: None))
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proc algebraicToPosition(s: string): tuple[row, col: int] {.inline.} =
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proc algebraicToPosition(s: string): Location {.inline.} =
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## Converts a square location from algebraic
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## notation to its corresponding row and column
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## in the chess grid (0 indexed)
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assert len(s) == 2
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result = (int(uint8(s[0]) - (uint8('a') - 1)), int(uint8(s[1]) - uint8('0')))
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if len(s) != 2:
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raise newException(ValueError, "algebraic position must be of length 2")
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var s = s.toLowerAscii()
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if s[0] notin 'a'..'h':
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raise newException(ValueError, &"algebraic position has invalid first character ('{s[0]}')")
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if s[1] notin '1'..'8':
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raise newException(ValueError, &"algebraic position has invalid second character ('{s[1]}')")
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let file = int(uint8(s[0]) - uint8('a'))
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var rank: int
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case s[1]:
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of '1':
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rank = 7
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of '2':
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rank = 6
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of '3':
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rank = 5
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of '4':
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rank = 4
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of '5':
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rank = 3
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of '6':
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rank = 2
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of '7':
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rank = 1
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of '8':
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rank = 0
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else:
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discard
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return (rank, file)
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proc getPiece*(self: ChessBoard, square: string): Piece =
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## Gets the piece on the given square
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## in algebraic notation
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let loc = square.algebraicToPosition()
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return self.grid[loc.row, loc.col]
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proc `$`*(self: ChessBoard): string =
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@ -84,12 +128,33 @@ proc `$`*(self: ChessBoard): string =
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result &= "\n- - - - - - - -"
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proc newChessboard: ChessBoard =
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## Returns a new, empty chessboard
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new(result)
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# Initialize all positions to a known default state.
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# This is useful in newChessBoardFromFEN
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result.pieces.black.king = (-1, -1)
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result.pieces.white.king = (-1, -1)
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result.pieces.black.queen = (-1, -1)
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result.pieces.white.queen = (-1, -1)
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result.pieces.black.rooks = [(-1, -1), (-1, -1)]
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result.pieces.white.rooks = [(-1, -1), (-1, -1)]
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result.pieces.black.bishops = [(-1, -1), (-1, -1)]
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result.pieces.white.bishops = [(-1, -1), (-1, -1)]
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result.pieces.black.knights = [(-1, -1), (-1, -1)]
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result.pieces.white.knights = [(-1, -1), (-1, -1)]
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result.pieces.black.pawns = [(-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1)]
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result.pieces.white.pawns = [(-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1), (-1, -1)]
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# Turns our flat sequence into an 8x8 grid
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result.grid = newMatrixFromSeq[Piece](empty, (8, 8))
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result.attacked = (@[], @[])
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result.enPassantSquare = Position(piece: Piece(kind: Empty, color: None), location: (-1, -1))
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proc newChessboardFromFEN*(state: string): ChessBoard =
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## Initializes a chessboard with the
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## state encoded by the given FEN string
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new(result)
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# Turns our flat sequence into an 8x8 grid
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result.grid = newMatrixFromSeq[Piece](empty, (8, 8))
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result = newChessboard()
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var
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# Current location in the grid
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row = 0
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@ -98,6 +163,8 @@ proc newChessboardFromFEN*(state: string): ChessBoard =
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section = 0
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# Current index into the FEN string
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index = 0
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# Temporary variable to store the piece
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piece: Piece
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# See https://en.wikipedia.org/wiki/Forsyth%E2%80%93Edwards_Notation
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while index <= state.high():
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var c = state[index]
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@ -110,13 +177,82 @@ proc newChessboardFromFEN*(state: string): ChessBoard =
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of 0:
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# Piece placement data
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case c.toLowerAscii():
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# Piece
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of 'r', 'n', 'b', 'q', 'k', 'p':
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result.grid[row, column] = Piece(kind: PieceKind(c.toLowerAscii()), color: if c.isUpperAscii(): White else: Black)
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# We know for a fact these values are in our
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# enumeration, so all is good
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{.push.}
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{.warning[HoleEnumConv]:off.}
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piece = Piece(kind: PieceKind(c.toLowerAscii()), color: if c.isUpperAscii(): White else: Black)
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{.pop.}
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case piece.color:
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of Black:
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case piece.kind:
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of Pawn:
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# Find first empty slot in the pieces array
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for i, e in result.pieces.black.pawns:
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if e == (-1, -1):
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result.pieces.black.pawns[i] = (row, column)
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break
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of Bishop:
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if result.pieces.black.bishops[0] == (-1, -1):
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result.pieces.black.bishops[0] = (row, column)
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else:
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result.pieces.black.bishops[1] = (row, column)
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of Knight:
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if result.pieces.black.knights[0] == (-1, -1):
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result.pieces.black.knights[0] = (row, column)
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else:
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result.pieces.black.knights[1] = (row, column)
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of Rook:
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if result.pieces.black.rooks[0] == (-1, -1):
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result.pieces.black.rooks[0] = (row, column)
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else:
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result.pieces.black.rooks[1] = (row, column)
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of Queen:
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result.pieces.black.queen = (row, column)
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of King:
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result.pieces.black.king = (row, column)
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else:
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discard
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of White:
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case piece.kind:
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of Pawn:
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for i, e in result.pieces.white.pawns:
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if e == (-1, -1):
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result.pieces.white.pawns[i] = (row, column)
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break
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of Bishop:
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if result.pieces.white.bishops[0] == (-1, -1):
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result.pieces.white.bishops[0] = (row, column)
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else:
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result.pieces.white.bishops[1] = (row, column)
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of Knight:
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if result.pieces.white.knights[0] == (-1, -1):
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result.pieces.white.knights[0] = (row, column)
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else:
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result.pieces.white.knights[1] = (row, column)
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of Rook:
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if result.pieces.white.rooks[0] == (-1, -1):
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result.pieces.white.rooks[0] = (row, column)
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else:
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result.pieces.white.rooks[1] = (row, column)
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of Queen:
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result.pieces.white.queen = (row, column)
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of King:
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result.pieces.white.king = (row, column)
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else:
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discard
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else:
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discard
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result.grid[row, column] = piece
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inc(column)
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of '/':
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# Next row
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inc(row)
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column = 0
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of '0'..'9':
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# Skip x columns
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let x = int(uint8(c) - uint8('0')) - 1
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if x > 7:
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raise newException(ValueError, "invalid skip value (> 8) in FEN string")
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@ -154,7 +290,8 @@ proc newChessboardFromFEN*(state: string): ChessBoard =
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# En passant target square
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case c:
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of '-':
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result.enPassantSquare.location = (-1, -1)
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# Field is already uninitialized to the correct state
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discard
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else:
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result.enPassantSquare.location = state[index..index+1].algebraicToPosition()
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# Just for cleanliness purposes, we fill in the other positional metadata as
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@ -1,5 +1,10 @@
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import board
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var b = newDefaultChessboard()
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echo b
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echo b.getPiece("a2")
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echo b.getPiece("a7")
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echo b.getPiece("a1")
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echo b.getPiece("a8")
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echo newChessboardFromFEN("rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1")[]
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