Tail recursive implementaion of doubling every other number in a list.

list_fun.ex

defmodule ListFun do

	def double_every_other([], acc), do: acc

	def double_every_other([head | nil], acc) do
		new_acc = [head * 2 | acc]
		double_every_other([], new_acc)
	end

	def double_every_other([head | tail], acc) when length(tail) == 0 do
		new_acc = [head * 2 | acc]
		double_every_other([], new_acc)
	end

	def double_every_other([head | tail], acc) do
		new_acc = [head * 2 | acc]
		[_skip | new_tail] = tail
		double_every_other(new_tail, new_acc)
	end
end