#!/usr/bin/ruby

class Walker
  Speed = 10     # class constant
  @@width = 60   # class variable
  @char = 'W'    # class instance variable

  def Walker.char #class method
    return @char
  end

  def Walker.setWidth newWidth # class method with parameter
    @@width = newWidth
  end

  def char #public instance method
    self.class.char # access class method from instance
  end

  def initialize # initialize is always private
    @counter = @@width / 2 # instance variable
  end

  def walk
    computeDirection
    updateCounter
    basicWalk
  end

  def run
    printf " " * 4; puts "-" * @@width
    (1..Speed).each { |line| printf "%2i: ", line; walk }
  end

  def getCounter
    return @counter
  end

  protected # accessable within instances of class and subclasses

  def left
    return -1
  end

  def right
    return 1
  end

  def forward
    return 0
  end

  def computeDirection
    @direction = forward
  end

  def basicWalk
    output = (0..@counter-1).collect{ char }
    puts "#{output}"
  end

  private # accessable within instances of class

  def updateCounter
    @counter += @direction * Speed / 10
    @counter = @@width if @counter > @@width
    @counter = 1  if @counter < 1
  end
end

class RandomWalker < Walker # subclass
  @char = 'R'

  def computeDirection
    @direction = rand < 0.5 ? left : right
  end
end

# example
if $0 == __FILE__
  Walker.new.run
  randomWalker = RandomWalker.new
  randomWalker.run
  Walker.setWidth 20
  Walker.new.run
  RandomWalker.new.run
  randomWalker.run 
end