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

@pdbradley yes, the signature of def and defp functions are different, so they are valid.

Keep in mind, that solution was written 3 years ago, when the language was slightly different :)

I am a newbie in Elixir coming from Ruby. I'd written my solution for this but I felt like it could be better and then I came across your solution. Brilliant! I'd never thought about matching that range as lo..hi in the function head, I was still doing the matching in the function body. 😄 I was also doing the guessing in each of the functions separately, your code helped me learn a lot!

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