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;
}