class Object
  def walk(&block)
    walk_object(Set.new, &block)
  end

  def walk_object(set, &block)
    return false if set.include?(self.object_id)

    set << self.object_id

    yield self

    walk_subobjects(set, &block)
  end

  def walk_subobjects(set, &block)
    instance_variables.each { |name|
      o = obj.instance_variable_get(name)
      o.walk_object(set, &block)
    }
  end
end

class Array
  def walk_subobjects(set, &block)
    super
    self.each { |o| o.walk_object(set, &block) }
  end
end

class Hash
  def walk_subobjects(set, &block)
    super
    keys.walk_subobjects(set, &block)
    values.walk_subobjects(set, &block)
  end
end