funpose.ex

defmodule Compositions do
  # "Call" composition
  #
  #     f = Enum.map(& &1+1) ||| Enum.reverse
  #
  #     f.([1,2,3])  #=> [4, 3, 2]
  #
  #     g = f.() ||| List.to_tuple
  #
  #     g.([1,2,3])  #=> {4, 3, 2}
  #
  defmacro c1 ||| c2 do
    quote do
      fn x ->
        x |> unquote(c1) |> unquote(c2)
      end
    end
  end

  # Function composition
  #
  #     ff = fn x -> Enum.map(x, & &1+1) end >>> &Enum.reverse/1
  #
  #     ff.([1,2,3])  #=> [4, 3, 2]
  #
  #     gg = ff >>> &List.to_tuple/1
  #
  #     gg.([1,2,3])  #=> {4, 3, 2}
  #
  defmacro f1 >>> f2 do
    quote do
      fn x ->
        unquote(f2).(unquote(f1).(x))
      end
    end
  end
end