programming_elixer6-chop.exs

defmodule Chop do
  def guess(actual, low..high) do
    next_guess = fn
      (n) when n == actual -> actual
      (n) when n  > actual -> guess(actual, low..n)
      (n) when n  < actual -> guess(actual, n..high)
    end

    n = div(low + high, 2)
    IO.puts "Is it #{n}?"
    next_guess.(n)
  end
end

This next_guess function looks an awful lot like a case statement. If we had been introduced to those yet, I think I would write it as such, and move the block to the end of the function.

Or one could simply invoke the function inline in truly anonymous fashion:

defmodule Chop do
  def guess(actual, low..high) do
    half = div(low + high, 2)
    IO.puts "Is it #{half}?"

    (fn
      (n) when n == actual -> actual
      (n) when n  > actual -> guess(actual, low..n)
      (n) when n  < actual -> guess(actual, n..high)
    end).(half)
  end
end