(defclass water ()())

(defclass chocolate (water)
  ((sugar
    :initarg :sugar
    :initform 5
    :reader get-sugar
    :accessor set-sugar
    :documentation "Sugar for hot chocolate")))

(defclass cafe (water)
  ((sugar
    :initarg :sugar
    :initform 3
    :reader get-sugar
    :accessor set-sugar
    :documentation "Sugar for hot cafe")))

(defclass dinner (chocolate cafe) ())

(defgeneric serving-drink (dinner)
  (:documentation "Serving the dring for the dinner"))

(defmethod serving-drink (cup dinner)
  (format t "The level of sugar is: ~d~%" (get-sugar cup)))