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yeschess
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Author SHA1 Message Date
  TiynGER 0ceb567048 structure: made a src folder and moved all source file into it 1 week ago
  TiynGER 6ad11fde2a chess: updating documentation 1 week ago
  TiynGER 9b68538b12 readme: specified plan for engine 1 week ago
  TiynGER c5cf2fd737 chess: refactoring setters and try 1 week ago
  TiynGER c4f7e3b98d chess: improved documentation and deleted unused stuff 1 week ago
  TiynGER 81d5d57e75 chess: refactoring getters 1 week ago
5 changed files with 880 additions and 829 deletions
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  4. +2
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  5. +25
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README.md
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# ychess
Attention: **The Chess engine is not finished yet.**
![ychess-logo](ychess.png)
ychess is a chess implementation written in nim.
A chess engine is planned.
ychess is a chess implementation and engine written in nim.
## Usage
@ -16,3 +17,14 @@ Testing is done by `einheit` by [jyapayne](https://github.com/jyapayne/einheit).
All legal chess moves are implemented in `chess.nim` and tested by the TestSuite
in `test.nim`.
You can simply run the tests with `nim c -r test.nim`.
## Documentation
Documentation is written into the code via DocGen.
For this reason it is not saved in this repository.
To extract it into html run `nim doc --project --index:on --outdir:htmldocs game.nim`
### Board Representation
Due to easier off the board checking a
[10x12](https://www.chessprogramming.org/10x12_Board) board is used.

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chess.nim
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import tables
from strutils import parseInt
import algorithm
type
Color* = enum
Black = -1, White = 1
## Board that saves the board
Board* = array[0..119, int]
## Board that checks if pieces moved
Moved* = array[0..119, bool]
## Castle rights for each player
CastleRights = tuple
wk: bool
wq: bool
bk: bool
bq: bool
## Game as object of different values
Game* = object
board*: Board
moved: Moved
toMove*: Color
previousBoard*: seq[Board]
previousCastleRights*: seq[CastleRights]
fiftyMoveCounter: int
## Move as object
Move* = object
start: int
dest: int
color: Color
prom: int
## Amount of pieces of a player
Pieces = tuple
p: int
k: int
b: int
r: int
q: int
const
# IDs for piece
BlockID* = 999
PawnID* = 1
KnightID* = 2
BishopID* = 3
RookID* = 4
QueenID* = 5
KingID* = 6
EnPassantID* = 7
# IDs that are saved in the array
Block* = BlockID
WPawn* = PawnID
WKnight* = KnightID
WBishop* = BishopID
WRook* = RookID
WQueen* = QueenID
WKing* = KingID
WEnPassant* = EnPassantID
BPawn* = -PawnID
BKnight* = -KnightID
BBishop* = -BishopID
BRook* = -RookID
BQueen* = -QueenID
BKing* = -KingID
BEnPassant* = EnPassantID
# Directions of movement
N = 10
S = -N
W = 1
E = -W
# Movement options for pieces (Bishop/Rook/Queen can repeat in the same direction)
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]
Bishop_Moves = [N+E, N+W, S+E, S+W]
Rook_Moves = [N, E, S, W]
Queen_Moves = [N, E, S, W, N+E, N+W, S+E, S+W]
King_Moves = [N, E, S, W, N+E, N+W, S+E, S+W]
King_Moves_White_Castle = [E+E, W+W]
Pawn_Moves_White = [N]
Pawn_Moves_White_Double = [N+N]
Pawn_Moves_White_Attack = [N+E, N+W]
let PieceChar = {
0: " ",
1: "P",
2: "N",
3: "B",
4: "R",
5: "Q",
6: "K",
7: " ",
-1: "p",
-2: "n",
-3: "b",
-4: "r",
-5: "q",
-6: "k",
-7: " ",
999: "-"
}.newTable
let FileChar = {
"a": 7,
"b": 6,
"c": 5,
"d": 4,
"e": 3,
"f": 2,
"g": 1,
"h": 0
}.newTable
const InsufficientMaterial = @[
#p, n, b, r, q
# lone kings
(0, 0, 0, 0, 0),
# knight only
(0, 0, 1, 0, 0),
# bishop only
(0, 1, 0, 0, 0),
# 2 knights
(0, 2, 0, 0, 0)
]
proc getField*(board: Board, field: int): int =
return board[field]
proc setField(board: var Board, field: int, val: int): bool {.discardable.} =
if (val in PieceChar):
try:
board[field] = val
return true
except Exception:
return false
proc getField*(moved: Moved, field: int): bool =
return moved[field]
proc setField(moved: var Moved, field: int, val: bool): bool {.discardable.} =
try:
moved[field] = val
return true
except Exception:
return false
proc checkInsufficientMaterial(board: Board): bool =
## Checks for combinations of pieces on a `board`, where no checkmate can be forced
var wp = 0
var wn = 0
var wb = 0
var wr = 0
var wq = 0
var bp = 0
var bn = 0
var bb = 0
var br = 0
var bq = 0
for field in board.low..board.high:
case board.getField(field):
of WPawn:
wp = wp + 1
of BPawn:
bp = bp + 1
of WKnight:
wn = wn + 1
of BKnight:
bn = bn + 1
of WBishop:
wb = wb + 1
of BBishop:
bb = bb + 1
of WRook:
wr = wr + 1
of BRook:
br = br + 1
of WQueen:
wq = wq + 1
of BQueen:
bq = bq + 1
else:
continue
let wpieces = (wp, wn, wb, wr, wq)
let bpieces = (bp, bn, bb, br, bq)
return (wpieces in InsufficientMaterial) and (bpieces in InsufficientMaterial)
proc initBoard(): Board =
## Create and return a board with pieces in starting position.
let board = [
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, WRook, WKnight, WBishop, WKing, WQueen, WBishop, WKnight, WRook, Block,
Block, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, Block,
Block, BRook, BKnight, BBishop, BKing, BQueen, BBishop, BKnight, BRook, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block]
return board
proc initBoard(board: array[0..63, int]): Board =
## Create and return a board with pieces in position of choice
let board = [
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, board[0], board[1], board[2], board[3], board[4], board[5],
board[6], board[7], Block,
Block, board[8], board[9], board[10], board[11], board[12], board[13],
board[14], board[15], Block,
Block, board[16], board[17], board[18], board[19], board[20], board[
21], board[22], board[23], Block,
Block, board[24], board[25], board[26], board[27], board[28], board[
29], board[30], board[31], Block,
Block, board[32], board[33], board[34], board[35], board[36], board[
37], board[38], board[39], Block,
Block, board[40], board[41], board[42], board[43], board[44], board[
45], board[46], board[47], Block,
Block, board[48], board[49], board[50], board[51], board[52], board[
53], board[54], board[55], Block,
Block, board[56], board[57], board[58], board[59], board[60], board[
61], board[62], board[63], Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block]
return board
proc initMoved(): Moved =
## Create and return a board of pieces moved.
var moved: Moved
return moved
proc initGame*(): Game =
## Create and return a Game object.
let game = Game(board: initBoard(), moved: initMoved(),
to_move: Color.White, previousBoard: @[], previousCastleRights: @[], fiftyMoveCounter: 0)
return game
proc initGame*(board: array[0..63, int], color: Color): Game =
## Create ad return a Game object based on a position of choice.
let board = initBoard(board)
let compare = initBoard()
var moved = initMoved()
var same_piece: bool
for ind in board.low..board.high:
same_piece = (board[ind] != compare[ind])
moved.setField(ind, same_piece)
let game = Game(board: board, moved: moved,
to_move: color, previousBoard: @[], previousCastleRights: @[], fiftyMoveCounter: 0)
return game
proc getMove*(start: int, dest: int, prom: int, color: Color): Move =
## Get a move object from `start` to `dest` with an eventual promition to `prom`
var move = Move(start: start, dest: dest, prom: prom * ord(color), color: color)
if (KnightID > prom or QueenID < prom):
move.prom = QueenID
return move
proc getMove*(start: int, dest: int, color: Color): Move =
## Get a move object from `start` to `dest` with automatic promition to `queen`
var move = Move(start: start, dest: dest, prom: QueenID * ord(color), color: color)
return move
proc echoBoard*(game: Game, color: Color) =
## Prints out the given `board` with its pieces as characters and line indices from perspecive of `color`.
var line_str = ""
if (color == Color.Black):
for i in countup(0, len(game.board)-1):
if (game.board.getField(i) == 999):
continue
line_str &= PieceChar[game.board[i]] & " "
if ((i+2) %% 10 == 0):
line_str &= $((int)((i)/10)-1) & "\n"
echo line_str
echo "h g f e d c b a"
else:
for i in countdown(len(game.board)-1, 0):
if (game.board.getField(i) == 999):
continue
line_str &= PieceChar[game.board[i]] & " "
if ((i-1) %% 10 == 0):
line_str &= $((int)((i)/10)-1) & "\n"
echo line_str
echo "a b c d e f g h"
proc fieldToInd*(file: string, line: int): int =
## Calculate board index from `file` and `line` of a chess board.
try:
return 1+(line+1)*10+FileChar[file]
except IndexDefect, ValueError:
return -1
proc fieldToInd*(field: string): int =
## Calculate board index from `field` of a chess board.
try:
return fieldToInd($field[0], parseInt($field[1]))
except IndexDefect, ValueError:
return -1
proc indToField*(ind: int): string =
## Calculate field name from board index `ind`.
let line = (int)ind/10-1
let file_ind = (ind)%%10-1
for file, i in FileChar:
if FileChar[file] == file_ind:
return $file & $line
proc genCastleRights(moved: Moved): CastleRights =
## Generate rights to castle from given `moved`
let wk = not moved.getField(fieldToInd("e1")) and not moved.getField(
fieldToInd("h1"))
let wq = not moved.getField(fieldToInd("e1")) and not moved.getField(
fieldToInd("a1"))
let bk = not moved.getField(fieldToInd("e8")) and not moved.getField(
fieldToInd("h8"))
let bq = not moved.getField(fieldToInd("e8")) and not moved.getField(
fieldToInd("a8"))
return (wk, wq, bk, bq)
proc notationToMove*(notation: string, color: Color): Move =
## Convert simplified algebraic chess `notation` to a move object, color of player is `color`.
try:
var move: Move
var start = fieldToInd(notation[0..1])
var dest = fieldToInd(notation[2..3])
move = getMove(start, dest, color)
if (len(notation) > 4):
var promStr = $notation[4]
var prom: int
case promStr:
of "Q":
prom = QueenID * ord(color)
of "R":
prom = RookID * ord(color)
of "B":
prom = BishopID * ord(color)
of "N":
prom = KnightID * ord(color)
move = getMove(start, dest, prom, color)
return move
except IndexError:
var move: Move
return move
proc genBishopDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a bishop with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Bishop_Moves:
dest = field+move
target = game.board.getField(dest)
while (target != 999 and (ord(color) * target <= 0) or target ==
EnPassantID or target == -EnPassantID):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -EnPassantID):
break
dest = dest+move
target = game.board.getField(dest)
return res
except IndexDefect:
return @[]
proc genRookDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a rook with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Rook_Moves:
dest = field+move
target = game.board.getField(dest)
while (target != 999 and (ord(color) * target <= 0) or target ==
EnPassantID or target == -EnPassantID):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -EnPassantID):
break
dest = dest+move
target = game.board.getField(dest)
return res
except IndexDefect:
return @[]
proc genQueenDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a queen with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Queen_Moves:
dest = field+move
target = game.board.getField(dest)
while (target != 999 and (ord(color) * target <= 0) or target ==
EnPassantID or target == -EnPassantID):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -EnPassantID):
break
dest = dest+move
target = game.board.getField(dest)
return res
except IndexDefect:
return @[]
proc genKingCastleDest(game: Game, field: int, color: Color): seq[int] =
## Generate possible castle destinations for a king with specific `color` located at index `field` of `game`
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
var half_dest: int
var half_target: int
for castle in King_Moves_White_Castle:
dest = field + castle
target = game.board.getField(dest)
half_dest = field + (int)castle/2
half_target = game.board.getField(half_dest)
if (target == 999 or (target != 0)):
continue
if (half_target == 999 or (half_target != 0)):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc genKingDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a king with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in King_Moves:
dest = field + move
target = game.board.getField(dest)
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != EnPassantID)):
continue
res.add(dest)
res.add(game.genKingCastleDest(field, color))
return res
except IndexDefect:
return @[]
proc genKnightDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a knight with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Knight_Moves:
dest = field + move
target = game.board.getField(dest)
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != EnPassantID)):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc genPawnAttackDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible attack destinations for a pawn with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for attacks in Pawn_Moves_White_Attack:
dest = field + (attacks * ord(color))
target = game.board.getField(dest)
if (target == 999 or ord(color) * target >= 0):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc genPawnDoubleDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible double destinations for a pawn with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for doubles in Pawn_Moves_White_Double:
dest = field + doubles * ord(color)
target = game.board.getField(dest)
if (game.moved.getField(field) or (target != 0) or (
game.board.getField(dest+(S*ord(color))) != 0)):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc genPawnDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a pawn with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Pawn_Moves_White:
dest = field + move * ord(color)
target = game.board.getField(dest)
if (target != 0 and target != ord(color) * EnPassantID):
continue
res.add(dest)
res.add(game.genPawnAttackDests(field, color))
res.add(game.genPawnDoubleDests(field, color))
return res
except IndexDefect:
return @[]
proc pieceOn(game: Game, color: Color, sequence: seq[int],
pieceID: int): bool =
## Check if a piece with `pieceID` of a given `color` is in a field described in a `sequence` in a `game`.
for check in sequence:
if game.board.getField(check) == ord(color) * -1 * pieceID:
return true
return false
proc isAttacked(game: Game, position: int, color: Color): bool =
## Check if a field is attacked by the opposite of `color` in a `game`.
var attacked = false
attacked = attacked or game.pieceOn(color, game.genPawnAttackDests(
position, color), PawnID)
attacked = attacked or game.pieceOn(color, game.genQueenDests(position,
color), QueenID)
attacked = attacked or game.pieceOn(color, game.genKingDests(position,
color), KingID)
attacked = attacked or game.pieceOn(color, game.genRookDests(position,
color), RookID)
attacked = attacked or game.pieceOn(color, game.genBishopDests(position,
color), BishopID)
attacked = attacked or game.pieceOn(color, game.genKnightDests(position,
color), KnightID)
return attacked
proc isInCheck*(game: Game, color: Color): bool =
## Check if the King of a given `color` is in check in a `game`.
var king_pos: int
for i in countup(0, game.board.high):
if game.board.getField(i) == ord(color) * KingID:
king_pos = i
return game.isAttacked(king_pos, color)
proc uncheckedMove(game: var Game, start: int, dest: int): bool {.discardable.} =
## Moves a piece if possible from `start` position to `dest` position.
## Doesnt check boundaries, checks, movement.
## returns true if the piece moved, else false
try:
let piece = game.board.getField(start)
if game.board.setField(start, 0):
if game.board.setField(dest, piece):
game.moved.setField(start, true)
game.moved.setField(dest, true)
return true
else:
game.board.setField(start, piece)
except IndexDefect, ValueError:
return false
proc moveLeadsToCheck(game: Game, start: int, dest: int,
color: Color): bool =
## Checks in a `game` if a move from `start` to `dest` puts the `color` king in check.
var check = game
check.uncheckedMove(start, dest)
return check.isInCheck(color)
proc removeEnPassant(board: var Board, color: Color): void =
## Removes every en passant of given `color` from the `game`.
for field in board.low..board.high:
if board.getField(field) == ord(color) * EnPassantID:
board.setField(field, 0)
proc genLegalKnightMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal knight moves starting from `field` in a `game` for a `color`.
if game.board.getField(field) != KnightID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genKnightDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalBishopMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal bishop moves starting from `field` in a `game` for a `color`.
if game.board.getField(field) != BishopID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genBishopDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalRookMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal rook moves starting from `field` in a `game` for a `color`.
if game.board.getField(field) != RookID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genRookDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalQueenMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal queen moves starting from `field` in a `game` for a `color`.
if game.board.getField(field) != QueenID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genQueenDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalKingMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal king moves starting from `field` in a `game` for a `color`.
if game.board.getField(field) != KingID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genKingDests(field, color)
for dest in moves:
if field - dest == W+W and game.isAttacked(dest+W, color):
continue
if field - dest == E+E and game.isAttacked(dest+E, color):
continue
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genPawnPromotion(move: Move, color: Color): seq[Move] =
## Generate all possible promotions of a `move` by `color`.
var promotions = newSeq[Move]()
let start = move.start
let dest = move.dest
if (90 < dest and dest < 99) or (20 < dest and dest < 29):
for piece in KnightID..QueenID:
promotions.add(getMove(start, dest, piece, color))
return promotions
proc genLegalPawnMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal pawn moves starting from `field` in a `game` for a `color`.
if game.board.getField(field) != PawnID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genPawnDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
var promotions = genPawnPromotion(getMove(field, dest, color), color)
if promotions != @[]:
res.add(promotions)
else:
res.add(getMove(field, dest, color))
return res
proc genLegalMoves*(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal moves starting from `field` in a `game` for a `color`.
var legal_moves = newSeq[Move]()
var target = ord(color) * game.board.getField(field)
if 0 < target and target < EnPassantID:
legal_moves = case target:
of PawnID:
game.genLegalPawnMoves(field, color)
of KnightID:
game.genLegalKnightMoves(field, color)
of BishopID:
game.genLegalBishopMoves(field, color)
of RookID:
game.genLegalRookMoves(field, color)
of QueenID:
game.genLegalQueenMoves(field, color)
of KingID:
game.genLegalKingMoves(field, color)
else:
@[]
return legal_moves
proc genLegalMoves*(game: Game, color: Color): seq[Move] =
## Generates all legal moves in a `game` for a `color`.
var legal_moves = newSeq[Move]()
for field in game.board.low..game.board.high:
legal_moves.add(game.genLegalMoves(field, color))
return legal_moves
proc castling(game: var Game, kstart: int, dest_kingside: bool,
color: Color): bool {.discardable.} =
## Tries to castle in a given `game` with the king of a given `color` from `start`.
## `dest_kingside` for kingside castling, else castling is queenside.
## This process checks for the legality of the move and performs the switch of `game.to_move`
try:
if game.toMove != color:
return false
var kdest = kstart
var rstart: int
var rdest: int
if (dest_kingside):
kdest = kstart + (E+E)
rstart = kstart + (E+E+E)
rdest = rstart + (W+W)
else:
rstart = kstart + (W+W+W+W)
rdest = rstart + (E+E+E)
kdest = kstart + (W+W)
if not game.moved.getField(kstart) and not game.moved.getField(rstart):
var check = false
if (dest_kingside):
check = check or game.isAttacked(kstart, color)
check = check or game.isAttacked(kstart+(E), color)
check = check or game.isAttacked(kstart+(E+E), color)
else:
check = check or game.isAttacked(kstart, color)
check = check or game.isAttacked(kstart+(W), color)
check = check or game.isAttacked(kstart+(W+W), color)
if check:
return false
game.uncheckedMove(kstart, kdest)
game.uncheckedMove(rstart, rdest)
game.toMove = Color(ord(game.toMove)*(-1))
return true
return false
except IndexDefect, ValueError:
return false
proc getPrevBoard*(game: Game): seq[Board] =
return game.previousBoard
proc checkedMove*(game: var Game, move: Move): bool {.discardable.} =
## Tries to make a move in a given `game` with the piece of a given `color` from `start` to `dest`.
## This process checks for the legality of the move and performs the switch of `game.to_move`
try:
let start = move.start
let dest = move.dest
let color = move.color
let prom = move.prom
if game.toMove != color:
return false
var sequence = newSeq[Move]()
let piece = game.board.getField(start)
var createEnPassant = false
var capturedEnPassant = false
var fiftyMoveRuleReset = false
var move: Move
move = getMove(start, dest, color)
if (piece == PawnID * ord(color)):
createEnPassant = dest in game.genPawnDoubleDests(start, color)
capturedEnPassant = (game.board.getField(dest) == -1 * ord(color) * EnPassantID)
fiftyMoveRuleReset = true
if (game.board.getField(move.dest) != 0):
fiftyMoveRuleReset = true
sequence.add(game.genLegalMoves(start, color))
if (move in sequence):
game.board.removeEnPassant(color)
if (piece == KingID * ord(color) and (start - dest == (W+W))):
return game.castling(start, true, color)
elif (piece == KingID * ord(color) and (start - dest == (E+E))):
return game.castling(start, false, color)
else:
game.uncheckedMove(start, dest)
game.toMove = Color(ord(game.toMove)*(-1))
if createEnPassant:
game.board.setField(dest-(N*ord(color)), EnPassantID * ord(color))
if capturedEnPassant:
game.board.setField(dest-(N*ord(color)), 0)
if ((90 < dest and dest < 99) or (20 < dest and dest < 29)) and
game.board.getField(dest) == PawnID * ord(color):
game.board.setField(dest, prom)
var prevBoard = game.previousBoard
var prevCastle = game.previousCastleRights
game.previousBoard.add(game.board)
game.previousCastleRights.add(game.moved.genCastleRights())
game.fiftyMoveCounter = game.fiftyMoveCounter + 1
if fiftyMoveRuleReset:
game.fiftyMoveCounter = 0
return true
except IndexDefect, ValueError:
return false
proc hasNoMoves(game: Game, color: Color): bool =
## Checks if a player of a given `color` has no legal moves in a `game`.
return (game.genLegalMoves(color) == @[])
proc isCheckmate*(game: Game, color: Color): bool =
## Checks if a player of a given `color` in a `game` is checkmate.
return game.hasNoMoves(color) and game.isInCheck(color)
proc threeMoveRep(game: Game): bool =
## Checks if a `rep`-times repitition happened on the last move of the `game`.
var lastState = game.previousBoard[game.previousBoard.high]
var lastCastleRights = game.previousCastleRights[game.previousBoard.high]
var reps = 0
for stateInd in (game.previousBoard.low)..(game.previousBoard.high):
if (game.previousBoard[stateInd] == lastState and game.previousCastleRights[
stateInd] == lastCastleRights):
reps = reps + 1
return reps >= 3
proc fiftyMoveRule(game: Game): bool =
## Checks if a draw with the fifty move rule is available in a `game`.
return game.fiftyMoveCounter >= 100
proc isDrawClaimable*(game: Game): bool =
## Checks if a draw is claimable by either player.
return game.threeMoveRep() or game.fiftyMoveRule()
proc isStalemate*(game: Game, color: Color): bool =
## Checks if a player of a given `color` in a `game` is stalemate.
return (game.hasNoMoves(color) and not game.isInCheck(color)) or
game.board.checkInsufficientMaterial()

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src/chess.nim
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import tables
from strutils import parseInt
type
Color* = enum
## `Color` describes the possible color of players.
Black = -1,
White = 1
Board* = array[0..119, int] ## \
## `Board` saves the position of the chess pieces.
Moved* = array[0..119, bool] ## \
## `Moved` saves the position of squares a piece moved on or from.
CastleRights = tuple
## `CastleRights` contains the rights to castling for each player.
wk: bool # `wk` describes White kingside castle
wq: bool # `wq` describes White queenside castle
bk: bool # `bk` describes Black kingside castle
bq: bool # `bq` describes Black queenside castle
Game* = object
## `Game` stores all important information of a chess game.
board*: Board
moved: Moved
toMove*: Color
previousBoard: seq[Board]
previousCastleRights: seq[CastleRights]
fiftyMoveCounter: int
Move* = object
## `Move` stores all important information for a move.
start: int
dest: int
color: Color
prom: int
PieceAmount = tuple
## `PieceAmount` describes the number of pieces of a certain type a/both
## player/s has/have.
p: int # `p` describes the amount of pawns.
n: int # `n` describes the amount of knights.
b: int # `b` describes the amount of bishops.
r: int # `r` describes the amount of rooks.
q: int # `q` describes the amount of queens.
const
Block* = 999 ## \
## `Block` is the value assigned to empty blocked fields in a board.
WPawn* = 1
## `WPawn` is the value assigned to a square in a board with a white pawn.
WKnight* = 2 ## \
## `WKnight` is the value assigned to a square in a board with a white
## knight.
WBishop* = 3 ## \
## `WBishop` is the value assigned to a square in a board with a white
## bishop.
WRook* = 4 ## \
## `WRook` is the value assigned to a square in a board with a white rook.
WQueen* = 5 ## \
## `WQueen` is the value assigned to a square in a board with a white
## 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 ## \
## `BKnight` is the value assigned to a square in a board with a black\
## knight.
BBishop* = -WBishop ## \
## `BBishop` is the value assigned to a square in a board with a black\
## bishop.
BRook* = -WRook ## \
## `BRook` is the value assigned to a square in a board with a black rook.
BQueen* = -WQueen ## \
## `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.
W = 1 ## `W` describes a move a field to the left from whites perspective.
E = -W ## `E` describes a move a field to the right from whites perspective.
# Directions for the pieces. Special moves are in separate arrays.
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] ## \
## `Knight_Moves` describes the possible knight moves.
Bishop_Moves = [N+E, N+W, S+E, S+W] ## \
## `Bishop_Moves` describes the possible 1 field distance bishop moves.
Rook_Moves = [N, E, S, W] ## \
## `Rook_Moves` describes the possible 1 field distance rook moves.
Queen_Moves = [N, E, S, W, N+E, N+W, S+E, S+W] ## \
## `Queen_Moves` describes the possible 1 field distance queen moves.
King_Moves = [N, E, S, W, N+E, N+W, S+E, S+W] ## \
## `King_Moves` describes the possible 1 field distance king moves.
King_Moves_White_Castle = [E+E, W+W] ## \
## `King_Moves` describes the possible king moves for castling.
Pawn_Moves_White = [N] ## \
## `Pawn_Moves_White` describes the possible 1 field distance pawn moves
## from whites perspective that are not attacks.
Pawn_Moves_White_Double = [N+N] ## \
## `Pawn_Moves_White_Double` describes the possible pawn 2 field distance
## moves from whites perspective.
Pawn_Moves_White_Attack = [N+E, N+W] ## \
## `Pawn_Moves_White` describes the possible 1 field distance pawn moves
## from whites perspective that are ttacks.
InsufficientMaterial: array[4, PieceAmount] = [
(0, 0, 0, 0, 0), # only kings
(0, 0, 1, 0, 0), # knight only
(0, 1, 0, 0, 0), # bishop only
(0, 2, 0, 0, 0) # 2 knights
] ## `InsufficientMaterial` describes the pieces where no checkmate can be
## forced.
let
PieceChar = {
0: " ",
WPawn: "P",
WKnight: "N",
WBishop: "B",
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 = {
"a": 7,
"b": 6,
"c": 5,
"d": 4,
"e": 3,
"f": 2,
"g": 1,
"h": 0
}.newTable ## \
# `FileChar` maps the files of the chessboard to numbers for better
# conversion.
proc checkInsufficientMaterial(board: Board): bool =
## Checks for combinations of pieces on a `board`, where no checkmate can be
## forced.
## Returns true if no player can force a checkmate to the other.
var wp = 0
var wn = 0
var wb = 0
var wr = 0
var wq = 0
var bp = 0
var bn = 0
var bb = 0
var br = 0
var bq = 0
for field in board.low..board.high:
case board[field]:
of WPawn:
wp = wp + 1
of BPawn:
bp = bp + 1
of WKnight:
wn = wn + 1
of BKnight:
bn = bn + 1
of WBishop:
wb = wb + 1
of BBishop:
bb = bb + 1
of WRook:
wr = wr + 1
of BRook:
br = br + 1
of WQueen:
wq = wq + 1
of BQueen:
bq = bq + 1
else:
continue
let wpieces: PieceAmount = (wp, wn, wb, wr, wq)
let bpieces: PieceAmount = (bp, bn, bb, br, bq)
return (wpieces in InsufficientMaterial) and (bpieces in InsufficientMaterial)
proc initBoard(): Board =
## Create and return a board with pieces in starting position.
let board = [
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, WRook, WKnight, WBishop, WKing, WQueen, WBishop, WKnight, WRook, Block,
Block, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, Block,
Block, BRook, BKnight, BBishop, BKing, BQueen, BBishop, BKnight, BRook, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block]
return board
proc initBoard(board: array[0..63, int]): Board =
## Create and return a board with pieces in position of choice, described in
## `board`.
let board = [
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, board[0], board[1], board[2], board[3], board[4], board[5],
board[6], board[7], Block,
Block, board[8], board[9], board[10], board[11], board[12], board[13],
board[14], board[15], Block,
Block, board[16], board[17], board[18], board[19], board[20], board[
21], board[22], board[23], Block,
Block, board[24], board[25], board[26], board[27], board[28], board[
29], board[30], board[31], Block,
Block, board[32], board[33], board[34], board[35], board[36], board[
37], board[38], board[39], Block,
Block, board[40], board[41], board[42], board[43], board[44], board[
45], board[46], board[47], Block,
Block, board[48], board[49], board[50], board[51], board[52], board[
53], board[54], board[55], Block,
Block, board[56], board[57], board[58], board[59], board[60], board[
61], board[62], board[63], Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block]
return board
proc initMoved(): Moved =
## Create and return a board of pieces moved.
var moved: Moved
return moved
proc initGame*(): Game =
## Create and return a Game object.
let game = Game(board: initBoard(), moved: initMoved(),
to_move: Color.White, previousBoard: @[], previousCastleRights: @[],
fiftyMoveCounter: 0)
return game
proc initGame*(board: array[0..63, int], color: Color): Game =
## Create ad return a Game 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 moved = initMoved()
var same_piece: bool
for ind in board.low..board.high:
same_piece = (board[ind] != compare[ind])
moved[ind] = same_piece
let game = Game(board: board, moved: moved,
to_move: color, previousBoard: @[], previousCastleRights: @[],
fiftyMoveCounter: 0)
return game
proc getMove*(start: int, dest: int, prom: int, color: Color): Move =
## Get a move object of the `color` player from `start` to `dest` with an
## eventual promition to `prom`.
var move = Move(start: start, dest: dest, prom: prom * ord(color), color: color)
if (WKnight > prom or WQueen < prom):
move.prom = WQueen
return move
proc getMove*(start: int, dest: int, color: Color): Move =
## Get a move object of the `color` player from `start` to `dest` with
## automatic promition to queen.
var move = Move(start: start, dest: dest, prom: WQueen * ord(color), color: color)
return move
proc echoBoard*(game: Game, color: Color) =
## Prints out the given `board` with its pieces as characters and line
## indices from perspecive of `color`.
var line_str = ""
if (color == Color.Black):
for i in countup(0, len(game.board)-1):
if (game.board[i] == 999):
continue
line_str &= PieceChar[game.board[i]] & " "
if ((i+2) %% 10 == 0):
line_str &= $((int)((i)/10)-1) & "\n"
echo line_str
echo "h g f e d c b a"
else:
for i in countdown(len(game.board)-1, 0):
if (game.board[i] == 999):
continue
line_str &= PieceChar[game.board[i]] & " "
if ((i-1) %% 10 == 0):
line_str &= $((int)((i)/10)-1) & "\n"
echo line_str
echo "a b c d e f g h"
proc fieldToInd*(file: string, line: int): int =
## Calculate and return board index from `file` and `line` of a chess board.
## Returns -1 if the `field` was not input correct.
try:
return 1+(line+1)*10+FileChar[file]
except IndexDefect, ValueError:
return -1
proc fieldToInd*(field: string): int =
## Calculate and return board index from `field` of a chess board.
## Returns -1 if the `field` was not input correct.
try:
return fieldToInd($field[0], parseInt($field[1]))
except IndexDefect, ValueError:
return -1
proc indToField*(ind: int): string =
## Calculate and returns field name from board index `ind`.
let line = (int)ind/10-1
let file_ind = (ind)%%10-1
for file, i in FileChar:
if FileChar[file] == file_ind:
return $file & $line
proc genCastleRights(moved: Moved): CastleRights =
## Generate and return rights to castle from given `moved`
let wk = not moved[fieldToInd("e1")] and not moved[fieldToInd("h1")]
let wq = not moved[fieldToInd("e1")] and not moved[fieldToInd("a1")]
let bk = not moved[fieldToInd("e8")] and not moved[fieldToInd("h8")]
let bq = not moved[fieldToInd("e8")] and not moved[fieldToInd("a8")]
return (wk, wq, bk, bq)
proc notationToMove*(notation: string, color: Color): Move =
## Convert and return simplified algebraic chess `notation` to a move object,
## color of player is `color`.
var move: Move
var start = fieldToInd(notation[0..1])
var dest = fieldToInd(notation[2..3])
move = getMove(start, dest, color)
if (len(notation) > 4):
var promStr = $notation[4]
var prom: int
case promStr:
of "Q":
prom = WQueen * ord(color)
of "R":
prom = WRook * ord(color)
of "B":
prom = WBishop * ord(color)
of "N":
prom = WKnight * ord(color)
move = getMove(start, dest, prom, color)
return move
proc genBishopDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a bishop with specific `color` located
## at index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for move in Bishop_Moves:
dest = field+move
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
while (target != 999 and (ord(color) * target <= 0) or target ==
WEnPassant or target == -WEnPassant):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -WEnPassant):
break
dest = dest+move
target = game.board[dest]
return res
proc genRookDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a rook with specific `color` located at
## index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for move in Rook_Moves:
dest = field+move
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
while (target != 999 and (ord(color) * target <= 0) or target ==
WEnPassant or target == -WEnPassant):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -WEnPassant):
break
dest = dest+move
target = game.board[dest]
return res
proc genQueenDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a queen with specific `color` located
## at index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for move in Queen_Moves:
dest = field+move
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
while (target != 999 and (ord(color) * target <= 0) or target ==
WEnPassant or target == -WEnPassant):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -WEnPassant):
break
dest = dest+move
target = game.board[dest]
return res
proc genKingCastleDest(game: Game, field: int, color: Color): seq[int] =
## Generate possible castle destinations for a king with specific `color`
## located at index `field` of `game`
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
var half_dest: int
var half_target: int
for castle in King_Moves_White_Castle:
dest = field + castle
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
half_dest = field + (int)castle/2
half_target = game.board[half_dest]
if (target == 999 or (target != 0)):
continue
if (half_target == 999 or (half_target != 0)):
continue
res.add(dest)
return res
proc genKingDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a king with specific `color`
## located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for move in King_Moves:
dest = field + move
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != WEnPassant)):
continue
res.add(dest)
res.add(game.genKingCastleDest(field, color))
return res
proc genKnightDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a knight with specific `color` located
## at index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for move in Knight_Moves:
dest = field + move
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != WEnPassant)):
continue
res.add(dest)
return res
proc genPawnAttackDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible attack destinations for a pawn with specific `color`
## located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for attacks in Pawn_Moves_White_Attack:
dest = field + (attacks * ord(color))
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
if (target == 999 or ord(color) * target >= 0):
continue
res.add(dest)
return res
proc genPawnDoubleDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible double destinations for a pawn with specific `color`
## located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for doubles in Pawn_Moves_White_Double:
dest = field + doubles * ord(color)
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
if (game.moved[field] or (target != 0) or (
game.board[dest+(S*ord(color))] != 0)):
continue
res.add(dest)
return res
proc genPawnDests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a pawn with specific `color` located at
## index `field` of `game`.
## Returns a sequence of possible indices to move to.
if (not field in game.board.low..game.board.high):
return @[]
var res = newSeq[int]()
var dest: int
var target: int
for move in Pawn_Moves_White:
dest = field + move * ord(color)
if (not dest in game.board.low..game.board.high):
continue
target = game.board[dest]
if (target != 0 and target != ord(color) * WEnPassant):
continue
res.add(dest)
res.add(game.genPawnAttackDests(field, color))
res.add(game.genPawnDoubleDests(field, color))
return res
proc pieceOn(game: Game, color: Color, sequence: seq[int],
pieceID: int): bool =
## Returns true if the `PieceID` of a given `color` is in `sequence` else
## wrong.
for check in sequence:
if game.board[check] == ord(color) * -1 * pieceID:
return true
return false
proc isAttacked(game: Game, position: int, color: Color): bool =
## Returns true if a `position` in a `game` is attacked by the opposite
## color of `color`.
var attacked = false
attacked = attacked or game.pieceOn(color, game.genPawnAttackDests(
position, color), WPawn)
attacked = attacked or game.pieceOn(color, game.genQueenDests(position,
color), WQueen)
attacked = attacked or game.pieceOn(color, game.genKingDests(position,
color), WKing)
attacked = attacked or game.pieceOn(color, game.genRookDests(position,
color), WRook)
attacked = attacked or game.pieceOn(color, game.genBishopDests(position,
color), WBishop)
attacked = attacked or game.pieceOn(color, game.genKnightDests(position,
color), WKnight)
return attacked
proc isInCheck*(game: Game, color: Color): bool =
## Returns true if the king of a given `color` is in check in a `game`.
var king_pos: int
for i in countup(0, game.board.high):
if game.board[i] == ord(color) * WKing:
king_pos = i
return game.isAttacked(king_pos, color)
proc uncheckedMove(game: var Game, start: int, dest: int): bool {.discardable.} =
## Moves a piece if possible from `start` position to `dest` position in a
## `game`.
let piece = game.board[start]
game.board[start] = 0
game.board[dest] = piece
game.moved[start] = true
game.moved[dest] = true
return true
proc moveLeadsToCheck(game: Game, start: int, dest: int,
color: Color): bool =
## Returns true if a move from `start` to `dest` in a `game` puts the `color`
## king in check.
var check = game
check.uncheckedMove(start, dest)
return check.isInCheck(color)
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 genLegalKnightMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal knight moves in a `game` starting from `field` for a
## `color`.
if game.board[field] != WKnight * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genKnightDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalBishopMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal bishop moves in a `game` starting from `field` for a
## `color`.
if game.board[field] != WBishop * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genBishopDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalRookMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal rook moves in a `game` starting from `field` for a
## `color`.
if game.board[field] != WRook * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genRookDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalQueenMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal queen moves in a `game` starting from `field` for a
## `color`.
if game.board[field] != WQueen * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genQueenDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genLegalKingMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal king moves in a `game` starting from `field` for a
## `color`.
if game.board[field] != WKing * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genKingDests(field, color)
for dest in moves:
if field - dest == W+W and game.isAttacked(dest+W, color):
continue
if field - dest == E+E and game.isAttacked(dest+E, color):
continue
if not game.moveLeadsToCheck(field, dest, color):
res.add(getMove(field, dest, color))
return res
proc genPawnPromotion(move: Move, color: Color): seq[Move] =
## Generate all possible promotions of a `move` by `color`.
var promotions = newSeq[Move]()
let start = move.start
let dest = move.dest
if (90 < dest and dest < 99) or (20 < dest and dest < 29):
for piece in WKnight..WQueen:
promotions.add(getMove(start, dest, piece, color))
return promotions
proc genLegalPawnMoves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal pawn moves in a `game` starting from `field` for a
## `color`.
if game.board[field] != WPawn * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.genPawnDests(field, color)
for dest in moves:
if not game.moveLeadsToCheck(field, dest, color):
var promotions = genPawnPromotion(getMove(field, dest, color), color)
if promotions != @[]:
res.add(promotions)
else:
res.add(getMove(field, dest, color))
return res
proc genLegalMoves*(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal moves in a `game` starting from `field` for a `color`.
var legal_moves = newSeq[Move]()
var target = ord(color) * game.board[field]
if 0 < target and target < WEnPassant:
legal_moves = case target:
of WPawn:
game.genLegalPawnMoves(field, color)
of WKnight:
game.genLegalKnightMoves(field, color)
of WBishop:
game.genLegalBishopMoves(field, color)
of WRook:
game.genLegalRookMoves(field, color)
of WQueen:
game.genLegalQueenMoves(field, color)
of WKing:
game.genLegalKingMoves(field, color)
else:
@[]
return legal_moves
proc genLegalMoves*(game: Game, color: Color): seq[Move] =
## Generates all legal moves in a `game` for a `color`.
var legal_moves = newSeq[Move]()
for field in game.board.low..game.board.high:
legal_moves.add(game.genLegalMoves(field, color))
return legal_moves
proc castling(game: var Game, kstart: int, dest_kingside: bool,
color: Color): bool {.discardable.} =
## Tries to castle in a given `game` with the king of a given `color` from
## `kstart`.
## `dest_kingside` for kingside castling, else castling is queenside.
## This process checks for the legality of the move and performs the switch
## of `game.to_move`
if game.toMove != color:
return false
var kdest = kstart
var rstart: int
var rdest: int
if (dest_kingside):
kdest = kstart + (E+E)
rstart = kstart + (E+E+E)
rdest = rstart + (W+W)
else:
rstart = kstart + (W+W+W+W)
rdest = rstart + (E+E+E)
kdest = kstart + (W+W)
if not game.moved[kstart] and not game.moved[rstart]:
var check = false
if (dest_kingside):
check = check or game.isAttacked(kstart, color)
check = check or game.isAttacked(kstart+(E), color)
check = check or game.isAttacked(kstart+(E+E), color)
else:
check = check or game.isAttacked(kstart, color)
check = check or game.isAttacked(kstart+(W), color)
check = check or game.isAttacked(kstart+(W+W), color)
if check:
return false
game.uncheckedMove(kstart, kdest)
game.uncheckedMove(rstart, rdest)
game.toMove = Color(ord(game.toMove)*(-1))
return true
return false
proc checkedMove*(game: var Game, move: Move): bool {.discardable.} =
## Tries to make a `move` in a given `game``.
## This process checks for the legality of the move and performs the switch
## of `game.to_move` with exception of castling (castling() switches).
let start = move.start
let dest = move.dest
let color = move.color
let prom = move.prom
if (game.toMove != color or start == -1 or dest == -1):
return false
var sequence = newSeq[Move]()
let piece = game.board[start]
var createEnPassant = false
var capturedEnPassant = false
var fiftyMoveRuleReset = false
var move: Move
move = getMove(start, dest, color)
if (piece == WPawn * ord(color)):
createEnPassant = dest in game.genPawnDoubleDests(start, color)
capturedEnPassant = (game.board[dest] == -1 * ord(color) * WEnPassant)
fiftyMoveRuleReset = true
if (game.board[move.dest] != 0):
fiftyMoveRuleReset = true
sequence.add(game.genLegalMoves(start, color))
if (move in sequence):
game.board.removeEnPassant(color)
if (piece == WKing * ord(color) and (start - dest == (W+W))):
return game.castling(start, true, color)
elif (piece == WKing * ord(color) and (start - dest == (E+E))):
return game.castling(start, false, color)
else:
game.uncheckedMove(start, dest)
game.toMove = Color(ord(game.toMove)*(-1))
if createEnPassant:
game.board[dest-(N*ord(color))] = WEnPassant * ord(color)
if capturedEnPassant:
game.board[dest-(N*ord(color))] = 0
if ((90 < dest and dest < 99) or (20 < dest and dest < 29)) and
game.board[dest] == WPawn * ord(color):
game.board[dest] = prom
var prevBoard = game.previousBoard
var prevCastle = game.previousCastleRights
game.previousBoard.add(game.board)
game.previousCastleRights.add(game.moved.genCastleRights())
game.fiftyMoveCounter = game.fiftyMoveCounter + 1
if fiftyMoveRuleReset:
game.fiftyMoveCounter = 0
return true
proc hasNoMoves(game: Game, color: Color): bool =
## Returns true if the `color` player has no legal moves in a `game`.
return (game.genLegalMoves(color) == @[])
proc isCheckmate*(game: Game, color: Color): bool =
## Returns true if the `color` player is checkmate in a `game`.
return game.hasNoMoves(color) and game.isInCheck(color)
proc threeMoveRep(game: Game): bool =
## Returns true if a 3-fold repitition happened on the last move of the
## `game`.
var lastState = game.previousBoard[game.previousBoard.high]
var lastCastleRights = game.previousCastleRights[game.previousBoard.high]
var reps = 0
for stateInd in (game.previousBoard.low)..(game.previousBoard.high):
if (game.previousBoard[stateInd] == lastState and game.previousCastleRights[
stateInd] == lastCastleRights):
reps = reps + 1
return reps >= 3
proc fiftyMoveRule(game: Game): bool =
## Returns true if a draw can be claimed by the 50 move rule in a `game`.
return game.fiftyMoveCounter >= 100
proc isDrawClaimable*(game: Game): bool =
## Returns true if a draw is claimable by either player.
return game.threeMoveRep() or game.fiftyMoveRule()
proc isStalemate*(game: Game, color: Color): bool =
## Returns true if the `color` player is stalemate in a `game`.
return (game.hasNoMoves(color) and not game.isInCheck(color)) or
game.board.checkInsufficientMaterial()

game.nim → src/game.nim
View File

@ -3,7 +3,8 @@ import rdstdin
import ./chess
proc runGame(): void =
proc runGame*(): void =
## Initializes and runs a game of chess.
var game = initGame()
var draw: string
game.echoBoard(game.toMove)

test.nim → src/test.nim
View File

@ -930,7 +930,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "5" & $str[ind+1] &
"6", Color.White))
self.check(test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "5")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "5")])
self.check(test)
str.reverse()
for ind, file in str:
@ -948,7 +948,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "5" & $str[ind+1] &
"6", Color.White))
self.check(test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "5")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "5")])
self.check(test)
method testCheckedMovePawnEnPassantTrueBlack() =
@ -980,7 +980,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "4" & $str[ind+1] &
"3", Color.Black))
self.check(test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "4")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "4")])
self.check(test)
str.reverse()
for ind, file in str:
@ -998,7 +998,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "4" & $str[ind+1] &
"3", Color.Black))
self.check(test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "4")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "4")])
self.check(test)
method testCheckedMovePawnEnPassantFalseWhite() =
@ -1030,7 +1030,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "5" & $str[ind+1] &
"6", Color.White))
self.check(not test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "5")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "5")])
self.check(not test)
str.reverse()
for ind, file in str:
@ -1048,7 +1048,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "5" & $str[ind+1] &
"6", Color.White))
self.check(not test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "5")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "5")])
self.check(not test)
method testCheckedMovePawnEnPassantFalseBlack() =
@ -1080,7 +1080,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "4" & $str[ind+1] &
"3", Color.Black))
self.check(not test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "4")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "4")])
self.check(not test)
str.reverse()
for ind, file in str:
@ -1098,7 +1098,7 @@ testSuite GameTest of TestSuite:
test = self.game.checkedMove(notationToMove($file & "4" & $str[ind+1] &
"3", Color.Black))
self.check(not test)
test = (0 == self.game.board.getField(fieldToInd($str[ind+1] & "4")))
test = (0 == self.game.board[fieldToInd($str[ind+1] & "4")])
self.check(not test)
## Tests for King moves
@ -1588,5 +1588,22 @@ testSuite GameTest of TestSuite:
else:
self.check(not test)
method testcheckedMoveFaultyInput() =
var test: bool
self.setup()
let startPos = self.game
test = self.game.checkedMove(notationToMove("aaaa", Color.White))
self.check(not test)
test = (self.game == startPos)
self.check(test)
test = self.game.checkedMove(notationToMove("1bb6&111", Color.White))
self.check(not test)
test = (self.game == startPos)
self.check(test)
test = self.game.checkedMove(notationToMove("e1g1sdfa", Color.White))
self.check(not test)
test = (self.game == startPos)
self.check(test)
when isMainModule:
einheit.runTests()

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