lazy.ex

defmacro thunk(b) do
    quote do: fn -> unquote(b) end
  end


  defmacro a ~> b do
    quote do
      unquote(a) = thunk(eval(unquote(b)))
    end
  end

  def eval(x) when is_function(x), do: eval(x.())
  def eval(x), do: x

  def foo(a), do: fn -> a + 1 end

  def add, do: fn a -> fn b -> thunk(eval(a) + eval(b)) end end

  def compose, do: fn f -> fn g -> fn x -> thunk(eval(f.(eval(g.(x))))) end end end

  def map do
    fn func ->
      fn list ->
          case eval(list) do
            [] -> []
            [head|tail] -> thunk([eval(func.(eval(head))) | eval(map().(func).(tail))])
          end
      end
    end
  end