2016 Update

Task/Perfect-numbers/Elixir/perfect-numbers.elixir

@@ -1,8 +1,13 @@
 defmodule RC do
   def is_perfect(1), do: false
   def is_perfect(n) when n > 1 do
-    (for i <- 1..div(n,2), rem(n,i)==0, do: i) |> Enum.sum == n
+    Enum.sum(factor(n, 2, [1])) == n
   end
+
+  defp factor(n, i, factors) when n <  i*i   , do: factors
+  defp factor(n, i, factors) when n == i*i   , do: [i | factors]
+  defp factor(n, i, factors) when rem(n,i)==0, do: factor(n, i+1, [i, div(n,i) | factors])
+  defp factor(n, i, factors)                 , do: factor(n, i+1, factors)
 end
 
 IO.inspect (for i <- 1..10000, RC.is_perfect(i), do: i)