Curious case of 'in'. Add in capability to strings in Elixir.

string_enumerable.ex

defimpl Enumerable, for: BitString do
  def count(string), do: {:ok, string |> String.length()}

  def member?(string, substring), do: {:ok, string |> String.contains?(substring)}

  def slice(string),
    do:
      {:ok, string |> String.length(),
       fn start_position, end_position ->
         string
         |> String.slice(start_position, end_position)
         |> to_list()
       end}

  def reduce(_list, {:halt, acc}, _fun), do: {:halted, acc}
  def reduce(list, {:suspend, acc}, fun) when list |> is_binary(), do: list |> to_list |> reduce({:suspend, acc}, fun)
  def reduce(list, {:suspend, acc}, fun), do: {:suspended, acc, &reduce(list, &1, fun)}
  def reduce(list, {:cont, acc}, fun) when list |> is_binary(), do: list |> to_list |> reduce({:cont, acc}, fun)
  def reduce([], {:cont, acc}, _fun), do: {:done, acc}
  def reduce([head | tail], {:cont, acc}, fun), do: tail |> reduce(fun.(head, acc), fun)

  defp to_list(string), do: string |> String.split("") |> Enum.reject(& &1 == "")
end