matrix.ex

  def from_list(list) do
    {_, matrix} = do_from_list(list, [], %{})
    matrix
  end

  defp do_from_list(list, indices, matrix) do
    Enum.reduce(list, {0, matrix}, fn
      sublist, {idx, matrix} when is_list(sublist) ->
        {sublist_idx, map} = do_from_list(sublist, [idx | indices], matrix)
        {idx + 1, map}
      item, {idx, matrix} ->
        coordinates =
          [idx | indices]
          |> Enum.reverse
          |> List.to_tuple

        {idx + 1, Map.put(matrix, coordinates, item)}
    end)
  end