chop.exs

defmodule Chop do
  def guess(actual, range) do
    midpoint(range)
    |> print_guess
    |> do_guess(actual, range)
  end

  defp do_guess(guess, actual, _) when guess == actual do
    IO.puts guess
  end

  defp do_guess(guess, actual, low.._) when guess > actual do
    guess(actual, low..(guess - 1))
  end

  defp do_guess(guess, actual, _..high) when guess < actual do
    guess(actual, (guess + 1)..high)
  end

  defp midpoint(low..high) do
    div((high - low), 2) + low
  end

  defp print_guess(guess) do
    IO.puts "Is it #{guess}"
    guess
  end
end