🚀 go-pugleaf

In article <CUTTING.92Sep30102223@skye.parc.xerox.com> cutting@skye.parc.xerox.com (Doug Cutting) writes:
>As it stands, class allocation approximates DEFVAR.

Except that the user of the slot doesn't have to know whether it's a
per-instance or a per-class variable.

For instance, you can have a class slot that's overridden by an instance
slot in a subclass.  For instance:

(defclass elephant ()
  (color :reader elephant-color
	 :allocation :class
	 :initform 'grey))

(defclass painted-elephant (elephant)
  (color :allocation :instance
	 :initarg :color
	 :writer (setf elephant-color)))

or vice versa:

(defclass bear ()
  (color :accessor bear-color
	 :initarg :color))

(defclass polar-bear ()
  (color :allocation :class
	 :initform 'white))

(defmethod (setf bear-color) (color (self polar-bear))
  (unless (eq color 'white)
    (error ...)))

-- 
Barry Margolin
System Manager, Thinking Machines Corp.

barmar@think.com          {uunet,harvard}!think!barmar