gistfile1.txt

lista = [1,2,3,3,4]

defmodule Misc do
    def dup([]) do
        {:done, nil}
    end
    def dup(list) do
        _dup(list, [])
    end
    def _dup([], result) do
        result
    end
    def _dup([head | tail], list) do
        result = tail -- [head]
        _dup(result, list ++ [head])
    end
end

Misc.dup(lista)