CS212 Exams
Spring 1999 - Final

Containers Containing Themselves?

(defclass <container> ()
   (contents :type <list>
             :accessor contents
             :initarg :contents
             :initvalue '()))

(defclass <contained> ()
   (location :type <container>
             :accessor location
             :initarg :location))

Using the above class definitions and the following method, show that it is possible for a container object to be contained in itself.

(defgeneric (place-in (obj <contained>) (c <container>)))

(defmethod (place-in (obj <contained>) (c <container>))
   (set! (contents c) (cons obj (contents c)))
   (set! (location obj) c))

Solution

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