   """
   @spec interval(non_neg_integer) :: Enumerable.t
   def interval(n) do
-    Stream.unfold 0, fn (count) ->
+    unfold 0, fn (count) ->
       :timer.sleep(n)
       {count, count + 1}
     end

  end

  @doc """
  Creates a stream that emits a single value after `n` milliseconds. The value emitted is
  `0`.
  
  ## Examples


  """
  @spec timer(non_neg_integer) :: Enumerable.t
  def timer(n) do
    take(interval(n), 1)
  end

  @doc """
