Elixir implementation of russian peasant algorithm

russian.exs

defmodule Russian do
  require Integer
  use Bitwise

  @doc ~S"""
   Multiply two integer using the Russian Peasant Algorithm
  ## Examples
    iex> Russian.mult(5,3)
    15
  """

  def mult(a, 0), do: 0
  def mult(a, 1), do: a

  def mult(a, b) when Integer.is_odd(b), do:
    a + mult(a <<< 1, b >>> 1)

  def mult(a, b), do:
    mult(a <<< 1, b >>> 1)
end