SETF of an &REST list.

["George J. Carrette" <GJC@MC.LCS.MIT.EDU>]

What you have to say is that SETF on the &REST list is not portable.
e.g. 

(defun foo (&rest l) (setf (car l) 'foo))

(defun test ()
 (let ((x (list nil)))
   (apply 'foo x)
   (car x)))
   
In NIL (or Maclisp for that matter): (test) ==> NIL
In zetalisp its always been that: (test) ==> FOO.

This is also the kind of behavior that may be different depending
on if a function is interpreted or compiled or traced etc.