Distru rpn example

rpn.ex

defmodule Distru.Rpn do

  def rpn_string(numbers) do
    String.split(numbers, " ")
  end

  def rpn(numbers) do
    Enum.reduce(numbers, [], fn term, acc ->
      case Integer.parse(term) do
        :error ->
          length = Enum.count(acc) - 2
          {begin, [item_a, item_b]} = Enum.split(acc, length)

          case term do
            "/" ->
              begin ++ [item_a / item_b]

            "*" ->
              begin ++ [item_a * item_b]

            "+" ->
              begin ++ [item_a + item_b]

            "-" ->
              begin ++ [item_a - item_b]
          end

        {number, ""} ->
          acc ++ [number]
      end
    end)
    |> Enum.at(0)
  end
end