A (somewhat) ugly but flexible solution to the fizzbuzz problem in Elixir

fizzbuzz.ex

defmodule FizzBuzz do
  @default_map %{3 => "Fizz", 5 => "Buzz"}
  @default_range_size 100

  def go() do
    go(@default_map, @default_range_size)
  end

  def go(map, range_size) 
    when is_map(map)
    and is_integer(range_size)
    and range_size > 1 do
    for i <- 1..range_size do
      get_combined_or_one(map, i)
    end
  end

  def go(map, range_size) do
    raise "Invalid arguments! Check if the provided map is a map and 
    if the range is an integer greater than 1"
  end
  

  defp get_combined_or_one(map, current_i) do
    Enum.reduce(Map.keys(map), &(&1 * &2))
      |> checks_out(current_i)
      |> return_combined_or_return_one(map, current_i)
  end

  defp return_combined_or_return_one(should_return_combined, map, current_i) do
    if should_return_combined do
      IO.puts Enum.reduce(Map.values(map), &(&2 <> &1))
    else
      IO.puts get_one_or_return_current(map, current_i)
    end
  end

  @doc """
  Helper functions below
  """
  defp checks_out(number, divider) do
    rem(divider, number) == 0
  end
  defp get_one_or_return_current(map, number) do
    map
      |> Enum.find(fn {key, _val} -> checks_out(key, number) end)
      |> get_or_default(map, number)
  end
  
  defp get_or_default(current_pair, map, num) do
    if current_pair do
      Map.get(map, elem(current_pair, 0))
    else
      num
    end
  end
end

FizzBuzz.go()