Xref: utzoo comp.lang.lisp:3371 comp.sys.ti.explorer:339
Path: utzoo!attcan!uunet!cs.utexas.edu!mailrus!ncar!boulder!!behrens
From: behrens@boulder (John Behrens)
Newsgroups: comp.lang.lisp,comp.sys.ti.explorer
Subject: Problem with CLOS
Message-ID: <22986@boulder.Colorado.EDU>
Date: 2 Jul 90 00:05:54 GMT
Sender: news@boulder.Colorado.EDU
Reply-To: behrens@boulder (John Behrens)
Distribution: na
Organization: University of Colorado, Boulder
Lines: 24

I spent the best part of a day chasing what turned out
to be the following:

(defmethod foo ((state state-class))
  (with-slots (bar) state   ;bar is a list
    (dotimes (i (length bar))
      (setf (nth i bar) <some value>))))

The behavior I got was that bar in *all* instances of state
was changed not just the instance passed into the method.

The following works:

(defmethod foo ((state state-class))
  (with-slots (bar) state   ;bar is a list
    (let ((baz
	    (make-sequence 'list (length bar) :initial-element 0)))
      (dotimes (i (length bar)(setf bar baz))
	(setf (nth i baz) <some value>)))))

I'm working in common LISP with CLOS on a MicroExplorer.
Does anyone have any idea what the problem is?

Jon