Minor improvements to board module

src/Chess/board.nim

@@ -15,6 +15,7 @@ import ../util/matrix
 
 
 import std/strutils
+import std/strformat
 
 
 type
@@ -36,12 +37,14 @@ type
     Position* = object
         piece*: Piece
         location*: tuple[row, col: int]
-    Board* = ref object
+    ChessBoard* = ref object
+        ## A chess board object
         grid: Matrix[Piece]
-        ply: PieceColor
+        # Currently active color
+        turn: PieceColor
         # Number of half moves since
-        # last piece capture. Used
-        # for the 50-move rule
+        # last piece capture or pawn movement.
+        # Used for the 50-move rule
         halfMoveClock: int
         # Full move counter. Increments
         # every 2 ply
@@ -67,7 +70,21 @@ proc algebraicToPosition(s: string): tuple[row, col: int] {.inline.} =
     result = (int(uint8(s[0]) - (uint8('a') - 1)), int(uint8(s[1]) - uint8('0')))
 
 
-proc newChessboardFromFEN*(state: string): Board =
+proc `$`*(self: ChessBoard): string =
+    result &= "- - - - - - - -"
+    for row in self.grid:
+        result &= "\n"
+        for piece in row:
+            if piece.kind == Empty:
+                result &= "  "
+            if piece.color == White:
+                result &= &"{char(piece.kind).toUpperAscii()} "
+            else:
+                result &= &"{char(piece.kind)} "
+    result &= "\n- - - - - - - -"
+
+
+proc newChessboardFromFEN*(state: string): ChessBoard =
     ## Initializes a chessboard with the
     ## state encoded by the given FEN string
     new(result)
@@ -110,11 +127,11 @@ proc newChessboardFromFEN*(state: string): Board =
                 # Active color
                 case c:
                     of 'w':
-                        result.ply = White
+                        result.turn = White
                     of 'b':
-                        result.ply = Black
+                        result.turn = Black
                     else:
-                        raise newException(ValueError, "invalid next move identifier in FEN string")
+                        raise newException(ValueError, "invalid active color identifier in FEN string")
             of 2:
                 # Castling availability
                 case c:
@@ -142,7 +159,7 @@ proc newChessboardFromFEN*(state: string): Board =
                         result.enPassantSquare.location = state[index..index+1].algebraicToPosition()
                         # Just for cleanliness purposes, we fill in the other positional metadata as
                         # well
-                        result.enPassantSquare.piece.color = if result.ply == Black: White else: Black
+                        result.enPassantSquare.piece.color = if result.turn == Black: White else: Black
                         result.enPassantSquare.piece.kind = Pawn
                         # Square metadata is 2 bytes long
                         inc(index)
@@ -167,4 +184,8 @@ proc newChessboardFromFEN*(state: string): Board =
                 raise newException(ValueError, "too many fields in FEN string")
         inc(index)
 
-    
+
+proc newDefaultChessboard*: ChessBoard =
+    ## Initializes a chessboard with the
+    ## starting position
+    return newChessboardFromFEN("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1")