piece.rb

class Piece
  attr_reader :color
  attr_accessor :pos

  def initialize(color, pos)
    @color = color  # :white or :black
    @pos = pos      # position = [x, y]
  end
  
  def dup
    self.class.new(@color, @pos)
  end

  private 
  def new_position(old_pos, vector)
    # Add a movement vector to a current position.
    [old_pos[0] + vector[0], old_pos[1] + vector[1]]
  end

  def remove_self_killing_moves(moves, board)
    # Take an array of potential moves and remove any moves that
    # kill pieces of the same color as self
    moves.select! do |move|
      board.piece_at_position(move).nil? || board.piece_at_position(move).color != @color
    end
    moves
  end

  def move_on_board?(move)
    (0...8).include?(move[0]) && (0...8).include?(move[1])
  end
end