rtn checksum in elixir

rtn_checksum.ex

"325081403"
  |> String.graphemes()                      # => ["3", "2", "5", "0", "8", "1", "4", "0", "3"]
  |> Stream.map(&String.to_integer/1)        # => [3, 2, 5, 0, 8, 1, 4, 0, 3]
  |> Stream.zip([3, 7, 1, 3, 7, 1, 3, 7, 1]) # => [{3, 3}, {2, 7}, {5, 1}, {0, 3}, {8, 7}, {1, 1}, {4, 3}, {0, 7}, {3, 1}]
  |> Stream.map(fn {a, b} -> a * b end)      # => [9, 14, 5, 0, 56, 1, 12, 0, 3]
  |> Enum.sum()                              # => 100
  |> rem(10) == 0                            # => true