my_enum.exs

defmodule MyEnum do
  def all?([head | tail], func \\ fn x -> x end) do
    func.(head) && all?(tail, func)
  end
  def all?([], _), do: true

  def each([], _), do: []
  def each([head | tail], func) do
    [func.(head), each(tail, func)]
  end

  # TODO: do something with unflatten lists
  def filter([], _), do: nil
  def filter([head | tail], func) when func.(head) == true do
    [head, filter(tail, func)]
  end
  def filter([head | tail], func) when func.(head) == false do
    [filter(tail, func)]
  end

  def split

  def take
end