interval_array.rb

class IntervalArray < Array
  attr_reader :range, :step_size
  def initialize(range, step_size = 1)
    super()
    @range = range
    @step_size = step_size
    regenerate
  end

  def range=(range)
    @range = range
    regenerate
  end

  def step_size=(step_size)
    @step_size = step_size
    regenerate
  end

  private
    def regenerate
      clear
      self << @range.min
      num_elements = (@range.count - 1) / @step_size
      while count <= num_elements
        self << last + @step_size
      end
    end
end

class Range
  def in_steps_of(n = 1)
    IntervalArray.new self, n
  end
end