defmodule Average do
  def median([]), do: nil
  def median(list) do
    len = length(list)
    sorted = Enum.sort(list)
    mid = div(len, 2)
    if rem(len,2) == 0, do: (Enum.at(sorted, mid-1) + Enum.at(sorted, mid)) / 2,
                      else: Enum.at(sorted, mid)
  end
end

median = fn list -> IO.puts "#{inspect list} => #{inspect Average.median(list)}" end
median.([])
Enum.each(1..6, fn i ->
  (for _ <- 1..i, do: :rand.uniform(6)) |> median.()
end)