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chess/game: base game completely implemented

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All moves including en-passant and castling are implemented.
Game now features a proof of concept game.
Some cleanup still needs to be done.
This commit is contained in:
TiynGER 2020-12-13 20:43:07 +01:00
parent b30aa89dc0
commit e30ff1f3ba
2 changed files with 284 additions and 127 deletions
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359
chess.nim
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@ -10,9 +10,15 @@ type
Moved* = array[0..119, bool]
## Game as object of different values
Game* = object
pieces: Pieces
pieces*: Pieces
moved: Moved
to_move: Color
to_move*: Color
## Move as object
Move* = object
start: int
dest: int
color: Color
prom: int
const
# IDs for piece
@ -51,6 +57,7 @@ const
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]
@ -102,6 +109,18 @@ proc init_board(): Pieces =
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block]
return board
proc get_move*(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 get_move*(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 init_moved(): Moved =
## Create and return a board of pieces moved.
var moved: Moved
@ -113,7 +132,7 @@ proc init_game*(): Game =
to_move: Color.White)
return game
proc get_field*(pieces: Pieces, field: int): int =
proc get_field(pieces: Pieces, field: int): int =
return pieces[field]
proc set_field(pieces: var Pieces, field: int, val: int): bool {.discardable.} =
@ -124,7 +143,7 @@ proc set_field(pieces: var Pieces, field: int, val: int): bool {.discardable.} =
except Exception:
return false
proc get_field*(moved: Moved, field: int): bool =
proc get_field(moved: Moved, field: int): bool =
return moved[field]
proc set_field(moved: var Moved, field: int, val: bool): bool {.discardable.} =
@ -178,8 +197,8 @@ proc ind_to_field*(ind: int): string =
if FileChar[file] == file_ind:
return $file & $line
proc gen_bishop_moves(game: Game, field: int, color: Color): seq[int] =
## Generate possible moves for a bishop with specific `color` located at index `field` of `board`.
proc gen_bishop_dests(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]()
@ -198,8 +217,8 @@ proc gen_bishop_moves(game: Game, field: int, color: Color): seq[int] =
except IndexDefect:
return @[]
proc gen_rook_moves(game: Game, field: int, color: Color): seq[int] =
## Generate possible moves for a rook with specific `color` located at index `field` of `board`.
proc gen_rook_dests(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]()
@ -218,8 +237,8 @@ proc gen_rook_moves(game: Game, field: int, color: Color): seq[int] =
except IndexDefect:
return @[]
proc gen_queen_moves(game: Game, field: int, color: Color): seq[int] =
## Generate possible moves for a queen with specific `color` located at index `field` of `board`.
proc gen_queen_dests(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]()
@ -238,8 +257,32 @@ proc gen_queen_moves(game: Game, field: int, color: Color): seq[int] =
except IndexDefect:
return @[]
proc gen_king_moves(game: Game, field: int, color: Color): seq[int] =
## Generate possible moves for a king with specific `color` located at index `field` of `board`.
proc gen_king_castle_dest(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.pieces.get_field(dest)
half_dest = field + (int) castle/2
half_target = game.pieces.get_field(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 gen_king_dests(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]()
@ -251,12 +294,13 @@ proc gen_king_moves(game: Game, field: int, color: Color): seq[int] =
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != EnPassantID)):
continue
res.add(dest)
res.add(game.gen_king_castle_dest(field, color))
return res
except IndexDefect:
return @[]
proc gen_knight_moves(game: Game, field: int, color: Color): seq[int] =
## Generate possible moves for a knight with specific `color` located at index `field` of `board`.
proc gen_knight_dests(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]()
@ -272,8 +316,8 @@ proc gen_knight_moves(game: Game, field: int, color: Color): seq[int] =
except IndexDefect:
return @[]
proc gen_pawn_attacks(game: Game, field: int, color: Color): seq[int] =
## Generate possible attacks for a pawn with specific `color` located at index `field` of `board`.
proc gen_pawn_attack_dests(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]()
@ -289,8 +333,8 @@ proc gen_pawn_attacks(game: Game, field: int, color: Color): seq[int] =
except IndexDefect:
return @[]
proc gen_pawn_doubles(game: Game, field: int, color: Color): seq[int] =
## Generate possible double moves for a pawn with specific `color` located at index `field` of `board`.
proc gen_pawn_double_dests(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]()
@ -306,8 +350,8 @@ proc gen_pawn_doubles(game: Game, field: int, color: Color): seq[int] =
except IndexDefect:
return @[]
proc gen_pawn_moves(game: Game, field: int, color: Color): seq[int] =
## Generate possible moves for a pawn with specific `color` located at index `field` of `board`.
proc gen_pawn_dests(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]()
@ -319,8 +363,8 @@ proc gen_pawn_moves(game: Game, field: int, color: Color): seq[int] =
if (target != 0 and target != ord(color) * EnPassantID):
continue
res.add(dest)
res.add(game.gen_pawn_attacks(field, color))
res.add(game.gen_pawn_doubles(field, color))
res.add(game.gen_pawn_attack_dests(field, color))
res.add(game.gen_pawn_double_dests(field, color))
return res
except IndexDefect:
return @[]
@ -336,21 +380,21 @@ proc piece_on(game: Game, color: Color, sequence: seq[int],
proc is_attacked(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.piece_on(color, game.gen_pawn_attacks(position,
attacked = attacked or game.piece_on(color, game.gen_pawn_attack_dests(position,
color), PawnID)
attacked = attacked or game.piece_on(color, game.gen_queen_moves(position,
attacked = attacked or game.piece_on(color, game.gen_queen_dests(position,
color), QueenID)
attacked = attacked or game.piece_on(color, game.gen_king_moves(position,
attacked = attacked or game.piece_on(color, game.gen_king_dests(position,
color), KingID)
attacked = attacked or game.piece_on(color, game.gen_rook_moves(position,
attacked = attacked or game.piece_on(color, game.gen_rook_dests(position,
color), RookID)
attacked = attacked or game.piece_on(color, game.gen_bishop_moves(position,
attacked = attacked or game.piece_on(color, game.gen_bishop_dests(position,
color), BishopID)
attacked = attacked or game.piece_on(color, game.gen_knight_moves(position,
attacked = attacked or game.piece_on(color, game.gen_knight_dests(position,
color), KnightID)
return attacked
proc is_in_check(game: Game, color: Color): bool =
proc is_in_check*(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.pieces.high):
@ -358,7 +402,7 @@ proc is_in_check(game: Game, color: Color): bool =
king_pos = i
return game.is_attacked(king_pos, color)
proc simple_move(game: var Game, start: int, dest: int): bool {.discardable.} =
proc unchecked_move(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
@ -376,9 +420,9 @@ proc simple_move(game: var Game, start: int, dest: int): bool {.discardable.} =
proc move_leads_to_check(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.
## Checks in a `game` if a move from `start` to `dest` puts the `color` king in check.
var check = game
check.simple_move(start, dest)
check.unchecked_move(start, dest)
return check.is_in_check(color)
proc remove_en_passant(pieces: var Pieces, color: Color): void =
@ -387,58 +431,120 @@ proc remove_en_passant(pieces: var Pieces, color: Color): void =
if pieces.get_field(field) == ord(color) * EnPassantID:
pieces.set_field(field,0)
proc checked_move*(game: var Game, start: int, dest: int, color: Color): 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:
if game.to_move != color:
return false
var sequence = newSeq[int]()
let piece = game.pieces.get_field(start)
var create_en_passant = false
var captured_en_passant = false
if (piece == PawnID * ord(color)):
sequence.add(game.gen_pawn_moves(start, color))
create_en_passant = dest in game.gen_pawn_doubles(start,color)
captured_en_passant = (game.pieces.get_field(dest) == -1 * ord(color) * EnPassantID)
if (piece == KnightID * ord(color)):
sequence.add(game.gen_knight_moves(start, color))
if (piece == BishopID * ord(color)):
sequence.add(game.gen_bishop_moves(start, color))
if (piece == RookID * ord(color)):
sequence.add(game.gen_rook_moves(start, color))
if (piece == QueenID * ord(color)):
sequence.add(game.gen_queen_moves(start, color))
if (piece == KingID * ord(color)):
sequence.add(game.gen_king_moves(start, color))
if (dest in sequence) and not game.move_leads_to_check(start, dest, color):
game.pieces.remove_en_passant(color)
game.simple_move(start, dest)
game.to_move = Color(ord(game.to_move)*(-1))
if create_en_passant:
game.pieces.set_field(dest-(N*ord(color)),EnPassantID * ord(color))
if captured_en_passant:
game.pieces.set_field(dest-(N*ord(color)),0)
return true
except IndexDefect, ValueError:
return false
proc gen_legal_knight_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal knight moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != KnightID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_knight_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc checked_promotion*(game: var Game, start: int, dest: int, color: Color,
prom: int): bool {.discardable.} =
## Tries to make a promotion to `prom` 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:
if game.pieces.get_field(start) != PawnID * ord(color) or (1 > prom or
prom > 5):
return false
if (90 < dest and dest < 99) or (20 < dest and dest < 29):
if (game.checked_move(start, dest, color)):
game.pieces.set_field(dest, prom)
return false
except IndexDefect, ValueError:
return false
proc gen_legal_bishop_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal bishop moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != BishopID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_bishop_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc castling*(game: var Game, kstart: int, dest_kingside: bool,
proc gen_legal_rook_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal rook moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != RookID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_rook_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_legal_queen_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal queen moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != QueenID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_queen_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_legal_king_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal king moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != KingID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_king_dests(field, color)
for dest in moves:
if field - dest == W+W and game.is_attacked(dest+W, color):
continue
if field - dest == E+E and game.is_attacked(dest+E, color):
continue
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_pawn_promotion(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(get_move(start, dest, piece, color))
return promotions
proc gen_legal_pawn_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal pawn moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != PawnID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_pawn_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
var promotions = gen_pawn_promotion(get_move(field, dest, color), color)
if promotions != @[]:
res.add(promotions)
else:
res.add(get_move(field, dest, color))
return res
proc gen_legal_moves*(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.pieces.get_field(field)
if 0 < target and target < EnPassantID:
legal_moves = case target:
of PawnID:
game.gen_legal_pawn_moves(field, color)
of KnightID:
game.gen_legal_knight_moves(field, color)
of BishopID:
game.gen_legal_bishop_moves(field, color)
of RookID:
game.gen_legal_rook_moves(field, color)
of QueenID:
game.gen_legal_queen_moves(field, color)
of KingID:
game.gen_legal_king_moves(field, color)
else:
@[]
return legal_moves
proc gen_legal_moves*(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.pieces.low..game.pieces.high:
legal_moves.add(game.gen_legal_moves(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.
@ -450,57 +556,74 @@ proc castling*(game: var Game, kstart: int, dest_kingside: bool,
var rstart: int
var rdest: int
if (dest_kingside):
kdest = kstart + (E+E) * ord(color)
rstart = kstart + (E+E+E) * ord(color)
rdest = rstart + (W+W) * ord(color)
kdest = kstart + (E+E)
rstart = kstart + (E+E+E)
rdest = rstart + (W+W)
else:
rstart = kstart + (W+W+W+W) * ord(color)
rdest = rstart + (E+E+E) * ord(color)
kdest = kstart + (W+W) * ord(color)
rstart = kstart + (W+W+W+W)
rdest = rstart + (E+E+E)
kdest = kstart + (W+W)
if not game.moved.get_field(kstart) and not game.moved.get_field(rstart):
var check = false
if (dest_kingside):
check = check or game.is_attacked(kstart, color)
check = check or game.is_attacked(kstart+(E)*ord(color), color)
check = check or game.is_attacked(kstart+(E+E)*ord(color), color)
check = check or game.is_attacked(kstart+(E), color)
check = check or game.is_attacked(kstart+(E+E), color)
else:
check = check or game.is_attacked(kstart, color)
check = check or game.is_attacked(kstart+(W)*ord(color), color)
check = check or game.is_attacked(kstart+(W+W)*ord(color), color)
check = check or game.is_attacked(kstart+(W), color)
check = check or game.is_attacked(kstart+(W+W), color)
if check:
return false
game.simple_move(kstart, kdest)
game.simple_move(rstart, rdest)
game.unchecked_move(kstart, kdest)
game.unchecked_move(rstart, rdest)
return true
return false
except IndexDefect, ValueError:
return false
proc checked_move*(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.to_move != color:
return false
var sequence = newSeq[Move]()
let piece = game.pieces.get_field(start)
var create_en_passant = false
var captured_en_passant = false
var move: Move
move = get_move(start, dest, color)
if (piece == PawnID * ord(color)):
create_en_passant = dest in game.gen_pawn_double_dests(start,color)
captured_en_passant = (game.pieces.get_field(dest) == -1 * ord(color) * EnPassantID)
sequence.add(game.gen_legal_moves(start, color))
if (move in sequence):
game.pieces.remove_en_passant(color)
if (piece == KingID * ord(color) and (start - dest == (W+W))):
game.castling(start, true, color)
elif (piece == KingID * ord(color) and (start - dest == (E+E))):
game.castling(start, false, color)
else:
game.unchecked_move(start, dest)
game.to_move = Color(ord(game.to_move)*(-1))
if create_en_passant:
game.pieces.set_field(dest-(N*ord(color)),EnPassantID * ord(color))
if captured_en_passant:
game.pieces.set_field(dest-(N*ord(color)),0)
if ((90 < dest and dest < 99) or (20 < dest and dest < 29)) and game.pieces.get_field(dest) == PawnID * ord(color):
game.pieces.set_field(dest, prom)
return true
except IndexDefect, ValueError:
return false
proc has_no_moves(game: Game, color: Color): bool =
## Checks if a player of a given `color` has no legal moves in a `game`.
var sequence = newSeq[(int,int)]()
for field_ind in game.pieces.low..game.pieces.high:
var target = ord(color) * game.pieces.get_field(field_ind)
if 0 < target and target < EnPassantID:
var possibilities = newSeq[int]()
case target:
of PawnID:
possibilities = game.gen_pawn_moves(field_ind, color)
of KnightID:
possibilities = game.gen_knight_moves(field_ind, color)
of BishopID:
possibilities = game.gen_bishop_moves(field_ind, color)
of RookID:
possibilities = game.gen_rook_moves(field_ind, color)
of QueenID:
possibilities = game.gen_queen_moves(field_ind, color)
of KingID:
possibilities = game.gen_king_moves(field_ind, color)
else:
continue
for dest in possibilities:
if (not game.move_leads_to_check(field_ind,dest,color)):
return false
return true
return (game.gen_legal_moves(color) == @[])
proc is_checkmate*(game: Game, color: Color): bool =
## Checks if a player of a given `color` in a `game` is checkmate.

52
game.nim
View File

@ -1,12 +1,46 @@
from strutils import parseInt
import rdstdin
import ./chess
# Testing
proc notation_to_move(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 = field_to_ind(notation[0..1])
var dest = field_to_ind(notation[2..3])
move = get_move(start, dest, color)
if (len(notation) > 4):
var prom_str = $notation[4]
var prom: int
case prom_str:
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 = get_move(start, dest, prom, color)
return move
except IndexError:
var move: Move
return move
var game = chess.init_game()
game.checked_move(field_to_ind("e2"),field_to_ind("e4"),Color.White)
game.checked_move(field_to_ind("e7"),field_to_ind("e6"),Color.Black)
game.checked_move(field_to_ind("g2"),field_to_ind("g4"),Color.White)
game.checked_move(field_to_ind("d8"),field_to_ind("h4"),Color.Black)
game.echo_board(Color.White)
echo game.is_checkmate(Color.White)
echo game.is_stalemate(Color.White)
proc run_game(): void =
var game = init_game()
game.echo_board(game.to_move)
while not game.is_checkmate(game.to_move):
echo "Make a move"
echo game.to_move
var move = readLine(stdin)
while not game.checked_move(notation_to_move(move, game.to_move)):
move = readLine(stdin)
game.echo_board(game.to_move)
if game.is_checkmate(game.to_move):
echo $game.to_move & " was checkmated"
if game.is_stalemate(game.to_move):
echo "Stalemate"
run_game()