From: Aron Griffis <ruby-talk@...1.net>
Date: 2002-04-25T00:24:27+09:00
Subject: Beginner's question

Hello,

I'm attempting to implement a game called "Twixt".  There are lots of
pages on the web describing the game, for example Google's first hit is

    http://www.flash.net/~markthom/html/twixt.html

I've read through some of the archives of this list and found an
implementation of a Matrix class that seems to meet my needs.  Here's
how I'm trying to use it:

  class Matrix < Array
    def initialize(height,width)
      super(height)
      self.each_index { |row| 
        self[row] = Array.new(width) 
        self[row].each_index { |col| self[row][col] = yield row, col }
      }
    end
  end

  class TwixtPeg
    RED = 0
    BLACK = 1
    def initialize(color)
      @color = color
      @barriers = []
    end

    attr :color
  end

  class TwixtBoard < Matrix
    def initialize(width = 24)
      super(width, width) { nil }
    end

    def to_s
      self.collect {|row| "#{row}"}.join "\n"
    end

    def []=(column, row, color)
      self[row][column] = TwixtPeg.new(color)
    end

    def [](column, row)
      self[row][column].color
    end
  end

  board = TwixtBoard.new
  print board, "\n"
  tb[0,0] = RED
  tb[23,23] = BLACK
  print board, "\n"

When I attempt to execute this code, I get the following error:

  ./mat.rb:5:in `[]=': wrong # of arguments(2 for 3) (ArgumentError)
          from ./mat.rb:5:in `initialize'
          from ./mat.rb:4:in `each_index'
          from ./mat.rb:4:in `initialize'
          from ./mat.rb:24:in `initialize'
          from ./mat.rb:40:in `new'
          from ./mat.rb:40

The problem appears to be that my overridden []= operator is
propagating back into the Matrix class.  I'm sure this is a beginner's
error, but what am I doing wrong?

I realize I could also implement this using a Matrix as an instance
variable in the TwixtBoard, for example:

  class TwixtBoard
    def initialize(width = 24)
      @m = Matrix.new(24, 24) { nil }
    end

    def []=(column, row, color)
      @m[row][column].color = TwixtPeg.new(color)
    end
  end

However I don't understand why my first attempt isn't successful.  Any
suggestions are welcome!

Thanks,
Aron