guessing_game.rb

class GuessRange
  attr_accessor :min, :max

  def initialize min, max
    @min, @max = min, max
  end

  def average
    (min + max) / 2
  end

  alias_method :mean, :average
end

class BinarySearchGuesser
  def initialize range
    @range = range
  end

  def guess
    @guess = @range.average
  end

  def too_low!
    @range.min = guess + 1
  end

  def too_high!
    @range.max = guess - 1
  end

  def max_guesses_required
    Math.log2(@range.max - @range.min).ceil
  end
end

class GuessingGame
  def initialize range = 1..100
    @guesser = BinarySearchGuesser.new GuessRange.new range.min, range.max
  end

  def play!
    puts "I think I can get it in at most #{@guesser.max_guesses_required} tries."
    @guesser.max_guesses_required.times do
      make_a_guess!
      break if get_feedback! == :won
    end
  end

  def make_a_guess!
    puts "I guess #{@guesser.guess}"
  end

  def taunt_or_flaunt!
    puts "Well well, it was pretty easy, I have to admit."
  end

  def get_feedback!
    loop do # Loop until they say something sensible.
      print "Am I high or low? Did I win? "
      case gets.chomp
      when /high/
        @guesser.too_high!
        return :too_high
      when /low/
        @guesser.too_low!
        return :too_low
      when /w[io]n/
        taunt_or_flaunt!
        return :won
      else
        puts "That didn't make any sense, try usin' English."
      end
    end
  end
end

GuessingGame.new.play!

Yay Ruby!!