(defvar *maximum* 100)
(defvar *minimum* 1)

(defun reset ()
  "Resets the minimum and maximum values"
  (format t "Okay, let's reset!~%")
  (setf *maximum* 100)
  (setf *minimum* 1)
  (guess))

(defun average (initial &rest remaining)
  "Gets the average of the values, requiring at least the intial value"
  (let* ((all (cons initial remaining))
         (len (length all))
         (sum (apply #'+ all)))
    (floor sum len)))

(defun higher ()
  "Sets the maximum to the average and guesses again"
  (setf *minimum* (average *maximum* *minimum*))
  (guess))

(defun lower ()
  "Sets the average to the minimum and guesses again"
  (setf *maximum* (average *maximum* *minimum*))
  (guess))

(defun guess ()
  "Prints a guess based on the average"
  (format t "I'm guessing ~a~%" (average *maximum* *minimum*)))