Ruby Tic-Tac-Toe

gistfile1.rb

class TicTacToe

  WINS = ['000000111', '000111000', '111000000',
          '001001001', '010010010', '100100100',
          '100010001', '001010100'].map! {|x| x.to_i(2) }

  attr_writer :crosses, :noughts

  def initialize
    reset
  end

  def check_win(bitboard)
    WINS.any? {|win| win & bitboard == win }
  end

  def reset
    @crosses = 0
    @noughts = 0
  end

  def legal_bitboard
    ~(@crosses | @noughts)
  end

  def legal_moves
    legal = legal_bitboard
    9.times.find_all {|move| legal & (1 << move) > 0}
  end

  def bit_moves
    legal_moves.map {|move| (1 << move)}
  end

  def to_s
    str = "Legal moves: {legal_moves.inspect}\n"
    str += "Game over: {over?}\n\n"
    9.times do |i|
      if @crosses & (1 << i) > 0
        str += ' X '
      elsif @noughts & (1 << i) > 0
        str += ' 0 '
      else
        str += ' - '
      end
      str += "\n" if i % 3 == 2
    end
    str + "\n"
  end

  def set_cur_board(board)
    if cur_player == 0
      @crosses = board
    else
      @noughts = board
    end
  end

  def cur_board
    cur_player == 0 ? @crosses : @noughts
  end

  # Game

  def copy
    tic = TicTacToe.new
    tic.crosses = @crosses
    tic.noughts = @noughts
    tic
  end

  def cur_player
    (bit_moves.length + 1) % 2
  end

  def make_move(move)
    bit_ms = bit_moves
    raise 'Illegal move' if move < 0 or move >= bit_ms.length
    set_cur_board(cur_board | bit_ms[move])
  end

  def num_moves
    bit_moves.length
  end

  def over?
    check_win(@crosses) or check_win(@noughts) or bit_moves.empty?
  end

  def outcomes
    if check_win(@crosses)
      [:WIN, :LOSS]
    elsif check_win(@noughts)
      [:LOSS, :WIN]
    else
      [:NF, :NF]
    end
  end

end