Problems with setf and structures

[Gregor.pa@Xerox.COM]

Using CLOS, there is a better solution to your problem.  Using CLOS and
taking advantage of one of the cleanup committee's proposals to cleanup
setf there is an even better solution.

Solution 1 - Using CLOS.

(defsetf foo-a set-foo-a)
(defsetf foo-b set-foo-b)
 .
 .

(defun test ()
  (let (x)
    (add-named-class 
      :name foo
      :superclasses ()
      :slot-specifications '((a :reader foo-a
				:writer set-foo-a)
			     (b :reader foo-b
				:writer set-foo-b)
			     .
			     .))

    (setq x (make-instance 'foo))

    (setf (foo-a x) 1)))

Solution 2 - Using CLOS and cleanup up setf

The basic difference is that you don't have to do the defsetfs.  The
reason is that setf is defined to expand into a well-know function when
there hasn't been an explicit defsetf done.

(defun test ()
  (let (x)
    (add-named-class 
      :name foo
      :superclasses ()
      :slot-specifications '((a :accessor foo-a)
			     (b :accessor foo-b)
			     .
			     .))

    (setq x (make-instance 'foo))

    (setf (foo-a x) 1)))
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