@ -8,8 +8,6 @@ type
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
@ -19,11 +17,11 @@ type
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
castleRights : CastleRights
Move * = object
## `Move` stores all important information for a move.
start : int
@ -109,8 +107,7 @@ const
( 0 , 1 , 0 , 0 , 0 ) , # bishop only
( 0 , 2 , 0 , 0 , 0 ) # 2 knights
] ## `InsufficientMaterial` describes the pieces where no checkmate can be
## forced.
## forced
let
PieceChar = {
@ -144,47 +141,65 @@ let
# `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 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 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 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 initBoard ( ) : Board =
## Create and return a board with pieces in starting position.
@ -229,16 +244,11 @@ proc initBoard(board: array[0..63, int]): Board =
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 ( ) ,
let game = Game ( board : initBoard ( ) ,
to_move : Color . White , previousBoard : @ [ ] , previousCastleRights : @ [ ] ,
fiftyMoveCounter : 0 )
fiftyMoveCounter : 0 , castleRights : ( true , true , true , true ) )
return game
proc initGame * ( board : array [ 0 .. 63 , int ] , color : Color ) : Game =
@ -246,30 +256,28 @@ proc initGame*(board: array[0..63, int], color: Color): Game =
## `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
var wk = false
var wq = false
var bk = false
var bq = false
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
for ind in board . low .. board . high :
same_piece = ( board [ ind ] ! = compare [ ind ] )
moved [ ind ] = same_piece
let game = Game ( board : board , moved : moved ,
let game = Game ( board : board ,
to_move : color , previousBoard : @ [ ] , previousCastleRights : @ [ ] ,
fiftyMoveCounter : 0 )
fiftyMoveCounter : 0 , castleRights : ( wk , wq , bk , bq ) )
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`.
@ -293,59 +301,88 @@ proc echoBoard*(game: Game, color: Color) =
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 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 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 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 ( ( target ! = 0 ) or (
game . board [ dest + ( S * ord ( color ) ) ] ! = 0 ) ) :
continue
if ( color = = Color . White and not ( field in fieldToInd ( " h2 " ) .. fieldToInd ( " a2 " ) ) ) :
continue
if ( color = = Color . Black and not ( field in fieldToInd ( " h7 " ) .. fieldToInd ( " a7 " ) ) ) :
continue
res . add ( dest )
return res
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 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 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 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 genBishopDests ( game : Game , field : int , color : Color ) : seq [ int ] =
## Generate possible destinations for a bishop with specific `color` located
@ -461,85 +498,6 @@ proc genKingDests(game: Game, field: int, color: Color): seq[int] =
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
@ -581,8 +539,22 @@ proc uncheckedMove(game: var Game, start: int, dest: int): bool {.discardable.}
let piece = game . board [ start ]
game . board [ start ] = 0
game . board [ dest ] = piece
game . moved [ start ] = true
game . moved [ dest ] = true
if ( start = = fieldToInd ( " e1 " ) or start = = fieldToInd ( " a1 " ) ) :
game . castleRights . wq = false
if ( start = = fieldToInd ( " e1 " ) or start = = fieldToInd ( " h1 " ) ) :
game . castleRights . wk = false
if ( start = = fieldToInd ( " e8 " ) or start = = fieldToInd ( " a8 " ) ) :
game . castleRights . bq = false
if ( start = = fieldToInd ( " e8 " ) or start = = fieldToInd ( " h8 " ) ) :
game . castleRights . bk = false
if ( dest = = fieldToInd ( " e1 " ) or dest = = fieldToInd ( " a1 " ) ) :
game . castleRights . wq = false
if ( dest = = fieldToInd ( " e1 " ) or dest = = fieldToInd ( " h1 " ) ) :
game . castleRights . wk = false
if ( dest = = fieldToInd ( " e8 " ) or dest = = fieldToInd ( " a8 " ) ) :
game . castleRights . bq = false
if ( dest = = fieldToInd ( " e8 " ) or dest = = fieldToInd ( " h8 " ) ) :
game . castleRights . bk = false
return true
proc moveLeadsToCheck ( game : Game , start : int , dest : int ,
@ -593,11 +565,31 @@ proc moveLeadsToCheck(game: Game, start: int, dest: int,
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 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 genLegalKnightMoves ( game : Game , field : int , color : Color ) : seq [ Move ] =
## Generates all legal knight moves in a `game` starting from `field` for a
@ -663,32 +655,6 @@ proc genLegalKingMoves(game: Game, field: int, color: Color): seq[Move] =
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 ] ( )
@ -730,15 +696,24 @@ proc castling(game: var Game, kstart: int, dest_kingside: bool,
var kdest = kstart
var rstart : int
var rdest : int
var rights = false
if ( dest_kingside ) :
kdest = kstart + ( E + E )
rstart = kstart + ( E + E + E )
rdest = rstart + ( W + W )
if ( color = = Color . White ) :
rights = game . castleRights . wk
else :
rights = game . castleRights . bk
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 ] :
if ( color = = Color . White ) :
rights = game . castleRights . bq
else :
rights = game . castleRights . bq
if ( rights ) :
var check = false
if ( dest_kingside ) :
check = check or game . isAttacked ( kstart , color )
@ -756,6 +731,12 @@ proc castling(game: var Game, 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 * ( 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
@ -799,7 +780,7 @@ proc checkedMove*(game: var Game, move: Move): bool {.discardable.} =
var prevBoard = game . previousBoard
var prevCastle = game . previousCastleRights
game . previousBoard . add ( game . board )
game . previousCastleRights . add ( game . moved . genC astleRights( ) )
game . previousCastleRights . add ( game . castleRights )
game . fiftyMoveCounter = game . fiftyMoveCounter + 1
if fiftyMoveRuleReset :
game . fiftyMoveCounter = 0
@ -833,6 +814,48 @@ proc isDrawClaimable*(game: Game): bool =
## Returns true if a draw is claimable by either player.
return game . threeMoveRep ( ) or game . fiftyMoveRule ( )
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 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
TiynGER