msort.ex

defmodule MSort do
  def msort([]), do: []
  def msort([e]), do: [e]
  def msort(list) do
    {left, right} = Enum.split(list, div(Enum.count(list), 2))
    merge(msort(left), msort(right))
  end

  def merge(left, []), do: left
  def merge([], right), do: right
  def merge(left, right) do
    [left_head | left_rest] = left
    [right_head | right_rest] = right
    if left_head < right_head do
      [left_head | merge(left_rest, right)]
    else
      [right_head | merge(right_rest, left)]
    end
  end
end

IO.puts(inspect MSort.msort([3,5,2,7]))