window-buffers

[ogus@math.berkeley.edu (Arthur E. Ogus)]

In programming fred, one has the ability to create new buffers and do
all sorts of things to them.  Furthermore, when a new fred window is
created, one can assign an existing buffer to serve as its
window-buffer.  However, I have not been able to figure out how to
change the window buffer from this one to another one once it has been
set.  Setf does not seem to work.  (e.g.
(ask mywindow (setf (window-buffer) newbuffer)) doesn't work.)
Does anyone out there know how to do this?