My solution for Chop guess exercise (Programming Elixir 1.3)

chop.exs

##############################
##Exercise: ModulesAndFunctions-6
defmodule Chop do
  def guess(actual, lo..hi) when (lo <= hi) and (actual in lo..hi) do
    current = guessing(lo, hi)
    IO.puts "Is it #{current}"
    guess(current, actual, lo..hi)
  end

  defp guess(value, actual, _) when value == actual, do: IO.puts value
  defp guess(value, actual, lo.._) when actual < value, do: guess actual, lo..(value - 1)
  defp guess(value, actual, _..hi) when actual > value, do: guess actual, (value + 1)..hi

  defp guessing(lo, hi), do: lo + div(hi - lo, 2)
end

Chop.guess 273, 1..1000
# Is it 500
# Is it 250
# Is it 375
# Is it 312
# Is it 281
# Is it 265
# Is it 273
# 273

Hello, @veelenga ! Although your solution works, I would like to make a couple of notes:

1. An extra work for the given exercise;
2. Both your solution and the book author's solution use private functions,
   which seems unfair to me, since this is the topic of the next section.

Thus, the solution can be rewritten as follows:

defmodule Chop do
  def guess(actual, low..high) do
    guessed = div(low + high, 2)
    IO.puts "Is it #{guessed}"
    processing_guessed =
      fn
        n when n == actual -> IO.puts n
        n when n > actual -> guess actual, low..(n - 1)
        n when n < actual -> guess actual, (n + 1)..high
      end
    processing_guessed.(guessed)
  end
end