Another update from ingydotnet^djgoku

Task/Digital-root/Elixir/digital-root.elixir

@@ -0,0 +1,25 @@
+defmodule Digital do
+  def root(n, base \\ 10), do: root(n, base, 0)
+
+  def root(n, base, ap) when n < base, do: {n, ap}
+  def root(n, base, ap) do
+    Integer.to_string(n, base)
+    |> String.codepoints
+    |> Enum.reduce(0, fn x,acc -> acc + String.to_integer(x, base) end)
+    |> root(base, ap+1)
+  end
+end
+
+data = [627615, 39390, 588225, 393900588225]
+Enum.each(data, fn n ->
+  {dr, ap} = Digital.root(n)
+  IO.puts "#{n} has additive persistence #{ap} and digital root of #{dr}"
+end)
+
+base = 16
+IO.puts "\nBase = #{base}"
+fmt = "~.#{base}B(#{base}) has additive persistence ~w and digital root of ~w~n"
+Enum.each(data, fn n ->
+  {dr, ap} = Digital.root(n, base)
+  :io.format fmt, [n, ap, dr]
+end)