chess: Moved replaced with CastleRights

Moved was a 10x12 1-d array, that stored bools.
It was only used for checking if a pawn moved (especially important for
the double move of the pawns) and if the other pieces moved (important
for checking if the player can castle or not).
The pawn moves are now checked by the starting position (pawns on the
second rank cant be already moved).
The castle rights of a game are expressed as CastleRights, a tuple with 4 bools.
This saves basically 116 boolean values.

src/chess.nim

@@ -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 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 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 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 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 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 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 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.genCastleRights())
+    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

src/game.nim

@@ -1,6 +1,3 @@
-from strutils import parseInt
-import rdstdin
-
 import ./chess
 
 proc runGame*(): void =