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chess: chess to fen notation added

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Now there is a method to turn a chess
object into a fen-string.
Additionally the enPassant handling was
changed.
There can be only one enPassant field
at a time.
So a new attribute was added to the chess
object that stores the field for the
enPassant capture.
If there is no enPassant field it will be set to -1.
master
TiynGER 4 years ago
parent d5ac25a642
commit a3c48fd50c
2 changed files with 80 additions and 116 deletions
Show Stats Download Patch File Download Diff File

136
src/chess.nim
Unescape View File

@ -23,8 +23,10 @@ type
toMove*: Color
previousBoard: seq[Board]
previousCastleRights: seq[CastleRights]
fiftyMoveCounter: int
halfMoveClock: int
fullMoveCounter*: int
castleRights: CastleRights
enPassantSquare: int
Move* = object
## `Move` stores all important information for a move.
start: int
@ -61,9 +63,6 @@ const
## queen.
WKing* = 6 ## \
## `WKing` is the value assigned to a square in a board with a white king.
WEnPassant = 7 ## \
## `WEnPassant` is assigned to a square in a board with an invisible white
## en passant pawn.
BPawn* = -WPawn ## \
## `BPawn` is the value assigned to a square in a board with a black pawn.
BKnight* = -WKnight ## \
@ -78,9 +77,6 @@ const
## `BQueen` is the value assigned to a square in a board with a black queen.
BKing* = -WKing ## \
## `BKing` is the value assigned to a square in a board with a black king.
BEnPassant = -WEnPassant ## \
## `BEnPassant` is assigned to a square in a board with an invisible black
## en passant pawn.
N = 10 ## `N` describes a move a field up the board from whites perspective.
S = -N ## `S` describes a move a field down the board from whites perspective.
E = 1 ## `E` describes a move a field to the right from whites perspective.
@ -124,14 +120,12 @@ let
WRook: "R",
WQueen: "Q",
WKing: "K",
WEnPassant: " ",
BPawn: "p",
BKnight: "n",
BBishop: "b",
BRook: "r",
BQueen: "q",
BKing: "k",
BEnPassant: " ",
}.newTable ## \
## `PieceChar` describes the representation for the pieceIDs for the cli.
FileChar = {
@ -260,39 +254,14 @@ proc initBoard(board: array[64, int]): Board =
proc initChess*(): Chess =
## Create and return a Chess object.
let chess = Chess(board: initBoard(),
to_move: Color.White, castleRights: (true, true, true, true))
return chess
proc initChess(board: array[64, int], color: Color): Chess =
## Create and return a Chess object based on a position of choice.
## `board` describes the pieces, `color` the color that is about to move.
let board = initBoard(board)
let compare = initBoard()
var wk: bool
var wq: bool
var bk: bool
var bq: bool
if (board[fieldToInd("e1")] == compare[fieldToInd("e1")]):
if (board[fieldToInd("a1")] == compare[fieldToInd("a1")]):
wq = true
if (board[fieldToInd("h1")] == compare[fieldToInd("h1")]):
wk = true
if (board[fieldToInd("e8")] == compare[fieldToInd("e8")]):
if (board[fieldToInd("a8")] == compare[fieldToInd("a8")]):
bq = true
if (board[fieldToInd("h8")] == compare[fieldToInd("h8")]):
bk = true
let chess = Chess(board: board,
to_move: color, castleRights: (wk, wq, bk, bq))
to_move: Color.White, castleRights: (true, true, true, true), fullMoveCounter: 1, enPassantSquare: -1)
return chess
proc initChess*(fen: string): Chess =
## Create and return a Chess object from `fen`.
var revPieceChar = toSeq(PieceChar.pairs).map(y => (y[1], y[0])).toTable
revPieceChar[" "] = Empty
var fenArr = fen.split(" ")
var squares: array[64, int]
var tmp: seq[int]
var squaresInd: int
for i, subc in fenArr[0].reversed():
if subc == '/':
@ -320,14 +289,60 @@ proc initChess*(fen: string): Chess =
castleRights.bk = true
if fenArr[2].contains("q"):
castleRights.bq = true
var enPassantSquare = -1
if fenArr[3] != "-":
if toMove == Color.White:
board[fieldToInd(fenArr[3])] = BEnPassant
else:
board[fieldToInd(fenArr[3])] = WEnPassant
var fiftyMoveCounter = parseInt(fenArr[4])
enPassantSquare = fieldToInd(fenArr[3])
let halfMoveClock = parseInt(fenArr[4])
let fullMoveCounter = parseInt(fenArr[5])
return Chess(board: board, toMove: toMove, castleRights: castleRights,
fiftyMoveCounter: fiftyMoveCounter)
halfMoveClock: halfMoveClock, fullMoveCounter: fullMoveCounter, enPassantSquare: enPassantSquare)
proc convertToFen*(chess: Chess): string =
## Build and return a fen string from a given `chess` object.
var pieces: string
var fen: string
var spaceOcc: int
var fileCounter = 0
for piece in chess.board.reversed:
if not (piece == Block):
if fileCounter == 8:
if spaceOcc != 0:
pieces &= $spaceOcc
spaceOcc = 0
pieces &= "/"
fileCounter = 0
if PieceChar[piece] == " ":
spaceOcc += 1
else:
if spaceOcc != 0:
pieces &= $spaceOcc
spaceOcc = 0
pieces &= PieceChar[piece]
fileCounter += 1
fen &= pieces & " "
if chess.toMove == Color.White:
fen &= "w "
else:
fen &= "b "
var castleR: string
if chess.castleRights.wk:
castleR &= "K"
if chess.castleRights.wq:
castleR &= "Q"
if chess.castleRights.bk:
castleR &= "k"
if chess.castleRights.bq:
castleR &= "q"
if castleR.isEmptyOrWhitespace:
castleR = "-"
fen &= castleR & " "
if chess.enPassantSquare != -1:
fen &= indToField(chess.enPassantSquare) & " "
else:
fen &= "- "
fen &= $chess.halfMoveClock & " " & $chess.fullMoveCounter
return fen
proc echoBoard*(chess: Chess, color: Color) =
## Prints out the given `board` with its pieces as characters and line
@ -363,10 +378,12 @@ proc genPawnAttackDests(chess: Chess, field: int, color: Color): seq[int] =
var target: int
for attacks in Pawn_Moves_White_Attack:
dest = field + (attacks * ord(color))
if (not dest in chess.board.low..chess.board.high):
if dest == chess.enPassantSquare:
res.add(dest)
if not dest in chess.board.low..chess.board.high:
continue
target = chess.board[dest]
if (target == Block or ord(color) * target >= 0):
if target == Block or ord(color) * target >= 0:
continue
res.add(dest)
return res
@ -407,7 +424,7 @@ proc genPawnDests(chess: Chess, field: int, color: Color): seq[int] =
if (not dest in chess.board.low..chess.board.high):
continue
target = chess.board[dest]
if (target != 0 and target != ord(color) * WEnPassant):
if (target != 0 and dest != chess.enPassantSquare):
continue
res.add(dest)
res.add(chess.genPawnAttackDests(field, color))
@ -428,7 +445,7 @@ proc genKnightDests(chess: Chess, field: int, color: Color): seq[int] =
if (not dest in chess.board.low..chess.board.high):
continue
target = chess.board[dest]
if (target == Block or (ord(color) * target > 0 and ord(color) * target != WEnPassant)):
if (target == Block or (ord(color) * target > 0)):
continue
res.add(dest)
return res
@ -448,10 +465,9 @@ proc genSlidePieceDests(chess: Chess, field: int, color: Color, moves: seq[
if (not dest in chess.board.low..chess.board.high):
continue
target = chess.board[dest]
while (target != Block and (ord(color) * target <= 0) or abs(target) ==
WEnPassant):
while (target != Block and (ord(color) * target <= 0)):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > BEnPassant):
if (ord(color) * target < 0):
break
dest = dest + move
target = chess.board[dest]
@ -514,7 +530,7 @@ proc genKingDests(chess: Chess, field: int, color: Color): seq[int] =
if (not dest in chess.board.low..chess.board.high):
continue
target = chess.board[dest]
if (target == Block or (ord(color) * target > 0 and ord(color) * target != WEnPassant)):
if (target == Block or (ord(color) * target > 0)):
continue
res.add(dest)
res.add(chess.genKingCastleDest(field, color))
@ -732,12 +748,6 @@ proc castling(chess: var Chess, kstart: int, dest_kingside: bool,
return true
return false
proc removeEnPassant(board: var Board, color: Color): void =
## Removes every en passant of given `color` from the `board`.
for field in board.low..board.high:
if board[field] == ord(color) * WEnPassant:
board[field] = 0
proc checkedMove*(chess: var Chess, move: Move): bool {.discardable.} =
## Tries to make a `move` in a given `chess``.
## This process checks for the legality of the move and performs the switch
@ -757,13 +767,13 @@ proc checkedMove*(chess: var Chess, move: Move): bool {.discardable.} =
move = getMove(start, dest, color)
if (piece == WPawn * ord(color)):
createEnPassant = dest in chess.genPawnDoubleDests(start, color)
capturedEnPassant = (chess.board[dest] == -1 * ord(color) * WEnPassant)
capturedEnPassant = (dest == chess.enPassantSquare)
fiftyMoveRuleReset = true
if (chess.board[move.dest] != 0):
fiftyMoveRuleReset = true
sequence.add(chess.genLegalMoves(start, color))
if (move in sequence):
chess.board.removeEnPassant(color)
chess.enPassantSquare = -1
if (piece == WKing * ord(color) and (start - dest == (W+W))):
return chess.castling(start, true, color)
elif (piece == WKing * ord(color) and (start - dest == (E+E))):
@ -772,19 +782,21 @@ proc checkedMove*(chess: var Chess, move: Move): bool {.discardable.} =
chess.uncheckedMove(start, dest)
chess.toMove = Color(ord(chess.toMove)*(-1))
if createEnPassant:
chess.board[dest - (N * ord(color))] = WEnPassant * ord(color)
chess.enPassantSquare = dest - (N * ord(color))
if capturedEnPassant:
chess.board[dest - (N * ord(color))] = 0
if ((90 < dest and dest < 99) or (20 < dest and dest < 29)) and
if ((fieldToInd("h8") < dest and dest < fieldToInd("a8")) or (fieldToInd("h1") < dest and dest < fieldToInd("a1"))) and
chess.board[dest] == WPawn * ord(color):
chess.board[dest] = prom
var prevBoard = chess.previousBoard
var prevCastle = chess.previousCastleRights
chess.previousBoard.add(chess.board)
chess.previousCastleRights.add(chess.castleRights)
chess.fiftyMoveCounter = chess.fiftyMoveCounter + 1
chess.halfMoveClock = chess.halfMoveClock + 1
if color == Color.Black:
chess.fullMoveCounter += 1
if fiftyMoveRuleReset:
chess.fiftyMoveCounter = 0
chess.halfMoveClock = 0
return true
proc isCheckmate*(chess: Chess, color: Color): bool =
@ -807,7 +819,7 @@ proc threeMoveRep(chess: Chess): bool =
proc isDrawClaimable*(chess: Chess): bool =
## Returns true if a draw is claimable by either player.
return chess.threeMoveRep() or chess.fiftyMoveCounter >= 100
return chess.threeMoveRep() or chess.halfMoveClock >= 100
proc checkInsufficientMaterial(board: Board): bool =
## Checks for combinations of pieces on a `board`, where no checkmate can be

60
src/engineTest.nim
Unescape View File

@ -12,85 +12,37 @@ testSuite ChessTest of TestSuite:
self.chess = initChess()
method testPieceEvalStalemate() =
self.chess = initChess([
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, WKing, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, BKing, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
], Color.Black)
var pieceEvaluation = self.chess.pieceEval()
self.chess = initChess("8/8/2k5/8/8/5K2/8/8 b - - 0 1")
var pieceEvaluation = self.chess.evaluate()
self.check(pieceEvaluation == 0)
method testBestMoveProm() =
self.chess = initChess([
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, WKing, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, WPawn, 0, BKing, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
], Color.White)
self.chess = initChess("8/2k1P3/8/8/8/5K2/8/8 w - - 0 1")
var testBestMove = self.chess.bestMove(2)
self.check(testBestMove.start != 0)
self.check(indToField(testBestMove.start) == "e7")
self.check(indToField(testBestMove.dest) == "e8")
method testBestMoveStopProm() =
self.chess = initChess([
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, WKing, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, WPawn, BKing, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
], Color.Black)
self.chess = initChess("8/2k1P3/8/8/8/5K2/8/8 b - - 0 1")
var testBestMove = self.chess.bestMove(2)
self.check(testBestMove.start != 0)
self.check(indToField(testBestMove.start) == "c7")
self.check(indToField(testBestMove.dest) == "d7")
method testBestMoveTacticBlack() =
self.chess = initChess([
0, 0, 0, 0, 0, 0, 0, 0,
0, WRook, 0, WKing, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, WPawn, 0, 0, 0, 0, 0,
0, BPawn, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, BRook, 0, 0, 0, BKing, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
], Color.Black)
self.chess = initChess("8/2k3r1/8/6p1/5P2/8/4K1R1/8 b - - 0 1")
var testBestMove = self.chess.bestMove(2)
self.check(testBestMove.start != 0)
self.check(indToField(testBestMove.start) != "g5" or indToField(
testBestMove.dest) != "f4")
method testBestMoveTacticWhite() =
self.chess = initChess([
0, 0, 0, 0, 0, 0, 0, 0,
0, WRook, 0, WKing, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, WPawn, 0, 0, 0, 0, 0, 0,
0, 0, BPawn, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, BRook, 0, 0, 0, BKing, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
], Color.White)
self.chess = initChess("8/2k3r1/8/5p2/6P1/8/4K1R1/8 w - - 0 1")
var testBestMove = self.chess.bestMove(2)
self.check(testBestMove.start != 0)
self.check(indToField(testBestMove.start) != "g4" or indToField(
testBestMove.dest) != "f5")
when isMainModule:
einheit.runTests()

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