gistfile1.ex

defimpl Enumerable, for: Bitmap do
  import :math, only: [log: 1]

  def reduce(bitmap, {:cont, acc}, fun) do
    bit_count =  Enum.count(bitmap)
    _reduce({bitmap, bit_count}, { :cont, acc }, fun)
  end

  defp _reduce({_bitmap, -1}, { :cont, acc }, _fun), do: { :done, acc }
                     
  defp _reduce({bitmap, bit_number}, { :cont, acc }, fun) do
    _reduce({bitmap, bit_number-1}, fun.(bitmap[bit_number], acc), fun)
  end

  def member?(value, bit_number) do
    { :ok, value[bit_number] }
  end

  def count(Bitmap[value: value]) do              
    { :ok, trunc(log(abs(value))/log(2)) + 1 }
  end
end