Flexible FizzBuzz implementation using Streams in Elixir

FizzBuzz.exs

defmodule FizzBuzz do
  @moduledoc """
  FizzBuzz outputs integers interspersed with configurable words
  at configurable intervals.
  """

  def fizzbuzz(count, words \\ [{3, "Fizz"}, {5, "Buzz"}]) do
    words
    |> Enum.map(&make_word_stream/1)
    |> Stream.zip
    |> Stream.with_index(1)
    |> Stream.map(&format_fizzbuzz/1)
    |> Stream.take(count)
    |> Enum.each(& IO.puts(&1))

    nil
  end

  defp make_word_stream({interval, word}) when interval > 0 do
    # This might not be such a great idea for large intervals, but fizzbuzz intervals
    # are usually on the order of 3 or 5. ;-)
    Stream.cycle(Enum.into([word], List.duplicate("", interval - 1)))
  end

  defp format_fizzbuzz({words, index}) do
    str =
      words
      |> Tuple.to_list
      |> Enum.reduce(fn (word, acc) -> acc <> word end)

    if str == "" do
      index
    else
      str
    end
  end
end