Class: Chess::Board

Inherits:
Object
  • Object
show all
Defined in:
ext/chess/chess.c,
ext/chess/chess.c

Overview

This class rappresents a chess board. The rappresentation of the board use bitboards where each bit represents a game position or state, designed for optimization of speed and/or memory or disk use in mass calculations. This ensures a fast library.

Instance Method Summary collapse

Instance Method Details

#[](square) ⇒ String

Returns the piece on the ‘square` of the chessboard. If there is no piece or the square is not valid return `nil`. Each square on the chessboard is represented by an integer according to the following scheme:

8 | 56 57 58 59 60 61 62 63
7 | 48 49 50 51 52 53 54 55
6 | 40 41 42 43 44 45 46 47
5 | 32 33 34 35 36 37 38 39
4 | 24 25 26 27 28 29 30 31
3 | 16 17 18 19 20 21 22 23
2 |  8  9 10 11 12 13 14 15
1 |  0  1  2  3  4  5  6  7
  +-------------------------
     a  b  c  d  e  f  g  h

Parameters:

  • square (Integer, String) —

    The square of the Chess::Board. Can be an integer between 0 and 63 or a string like ‘a2’, ‘c5’…

Returns:

  • (String) —

    The symbol that identify the piece _(‘P’, ‘R’, ‘N’, ‘B’, ‘Q’, ‘K’)_. Upcase for a white piece, downcase for a black piece.



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# File 'ext/chess/chess.c', line 446

VALUE
board_get_piece (VALUE self, VALUE square)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  int i;
  if (TYPE (square) == T_STRING)
    i = coord_to_square (StringValuePtr (square));
  else
    i = FIX2INT (square);
  char piece = board->placement[i];
  if (i < 0 || i > 63 || !piece)
    return Qnil;
  else
    return rb_str_new (&piece, 1);
}

#active_color ⇒ Boolean

Returns the active color: ‘false` means white turn, `true` means black turn.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 565

VALUE
board_active_color (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (board->active_color)
    return Qtrue;
  else
    return Qfalse;
}

#check? ⇒ Boolean

Returns ‘true` if the king of the color that has the turn is in check, `false` otherwise.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 468

VALUE
board_king_in_check (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (king_in_check (board, board->active_color))
    return Qtrue;
  else
    return Qfalse;
}

#checkmate? ⇒ Boolean

Returns ‘true` if the king of the color that has the turn is in checkmate, `false` otherwise.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 484

VALUE
board_king_in_checkmate (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (king_in_checkmate (board, board->active_color))
    return Qtrue;
  else
    return Qfalse;
}

#fifty_move_rule? ⇒ Boolean

Returns ‘true` if a player can claim draw by the fifty-move rule, `false` otherwise.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 548

VALUE
board_fifty_move_rule (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (fifty_move_rule (board))
    return Qtrue;
  else
    return Qfalse;
}

#fullmove_number ⇒ Integer

Returns the fullmove number: the number of the full move. It starts at 1, and * is incremented after black’s move.

Returns:

  • (Integer) 


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# File 'ext/chess/chess.c', line 597

VALUE
board_fullmove_number (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  return INT2FIX (board->fullmove_number);
}

#generate_all_moves ⇒ Array<String>

Generate all legal moves for the current board position.

Examples:

:001 > g = Chess::Game.new
 => #<Chess::Game:0x007f88a529fa88>
:002 > g.board.generate_all_moves
 => ["Na3", "Nc3", "Nf3", "Nh3", "a3", "a4", "b3", "b4", "c3", "c4", "d3", "d4", "e3", "e4", "f3", "f4", "g3", "g4", "h3", "h4"]

Returns:

  • (Array<String>) —

    Returns all legal moves that can be performed in the current board position. The moves are in short algebraic chess notation format.



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# File 'ext/chess/chess.c', line 655

VALUE
board_generate_all_moves (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  VALUE moves = rb_ary_new ();
  Board new_board;
  char *move_done;
  char capture;
  for (int i = 0; i < 64; i++)
    for (int j = 0; j < 64; j++)
      if (pseudo_legal_move (board, i, j))
        {
          move_done = castling (board, castling_type (board, i, j), &new_board);
          if (move_done || try_move (board, i, j, 'Q', &new_board, &move_done, &capture))
            rb_ary_push (moves, rb_str_new2 (move_done));
        }
  return moves;
}

#generate_moves(square) ⇒ Array<String>

Generate all legal moves for the piece in ‘square` position.

Examples:

:001 > g = Chess::Game.new
 => #<Chess::Game:0x007f88a529fa88>
:002 > g.board.generate_moves('b1')
 => ["Na3", "Nc3"]

Parameters:

  • square (Integer, String) —

    The square of the Chess::Board. Can be an integer between 0 and 63 or a string like ‘a2’, ‘c5’…

Returns:

  • (Array<String>) —

    Returns all legal moves that the piece in ‘square` position can perform. The moves are in short algebraic chess notation format.



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# File 'ext/chess/chess.c', line 619

VALUE
board_generate_moves (VALUE self, VALUE square)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  int from;
  if (TYPE (square) == T_STRING)
    from = coord_to_square (StringValuePtr (square));
  else
    from = FIX2INT (square);
  VALUE moves = rb_ary_new ();
  Board new_board;
  char *move_done;
  char capture;
  for (int i = 0; i < 64; i++)
    if (pseudo_legal_move (board, from, i))
      {
        move_done = castling (board, castling_type (board, from, i), &new_board);
        if (move_done || try_move (board, from, i, 'Q', &new_board, &move_done, &capture))
          rb_ary_push (moves, rb_str_new2 (move_done));
      }
  return moves;
}

#halfmove_clock ⇒ Integer

Returns the halfmove clock that is the number of halfmoves since the last pawn advance or capture. This is used to determine if a draw can be claimed under the fifty-move rule.

Returns:

  • (Integer) 


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# File 'ext/chess/chess.c', line 583

VALUE
board_halfmove_clock (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  return INT2FIX (board->halfmove_clock);
}

#insufficient_material? ⇒ Boolean

Returns ‘true` if the board has insufficient material to checkmate, `false` otherwise.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 516

VALUE
board_insufficient_material (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (insufficient_material (board))
    return Qtrue;
  else
    return Qfalse;
}

#only_kings? ⇒ Boolean

Returns ‘true` if on the board there are only the two kings, `false` otherwise.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 532

VALUE
board_only_kings (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (only_kings (board))
    return Qtrue;
  else
    return Qfalse;
}

#placement {|piece, index| ... } ⇒ Board, Array<String>

Cycle the Chess::Board squares.

Yields:

  • (piece, index) —

    Calls ‘block` once for each square in the Chess::Board, passing the `piece` in the square and the `index` as parameters.

Returns:

  • (Board) —

    Returns ‘self` if a block is given.

  • (Array<String>) —

    Returns the array of pieces if no block is given.



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# File 'ext/chess/chess.c', line 397

VALUE
board_placement (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (!rb_block_given_p ())
    {
      VALUE placement = rb_ary_new ();
      for (int i = 0; i < 64; i++)
        {
          char piece = board->placement[i];
          rb_ary_push (placement, rb_str_new (&piece, 1));
        }
      return placement;
    }
  else
    {
      for (int i = 0; i < 64; i++)
        {
          char piece = board->placement[i];
          rb_yield_values (2, rb_str_new (&piece, 1), INT2FIX (i));
        }
      return self;
    }
}

#stalemate? ⇒ Boolean

Returns ‘true` if the pieces of the color that has the turn are in stalemate, `false` otherwise.

Returns:

  • (Boolean) 


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# File 'ext/chess/chess.c', line 500

VALUE
board_stalemate (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  if (stalemate (board, board->active_color))
    return Qtrue;
  else
    return Qfalse;
}

#to_fen ⇒ String

Returns the FEN string of the board.

Returns:

  • (String) 


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# File 'ext/chess/chess.c', line 680

VALUE
board_to_fen (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  char *fen = to_fen (board);
  VALUE rb_fen = rb_str_new2 (fen);
  free (fen);
  return rb_fen;
}

#to_s ⇒ String

Chess::Board to string.

Returns:

  • (String) 


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# File 'ext/chess/chess.c', line 696

VALUE
board_to_s (VALUE self)
{
  Board *board;
  Data_Get_Struct (self, Board, board);
  char *s = print_board (board);
  VALUE rb_s = rb_str_new2 (s);
  free (s);
  return rb_s;
}