anchor.diff:      :for impl :in (list (implementation))  ; for multi-frame support in the future...
       :do (let ((vf (make-virtual-frame impl (get-frame impl))))
             (setf (gethash impl *virtual-frame-map*) vf)
  -          (map-frame (implementation) (virtual-frame-current vf)))))
  +          (switch-current-frame vf (virtual-frame-current vf)))))
   
   (defun enabled-frame-multiplexer-p ()
     (variable-value 'frame-multiplexer :global))
  
positive.code:                              :id/frame-table id/frame-table
                               :current frame)))
        vf)))
  
  (defun find-unused-frame-id (virtual-frame)
    (position-if #'null (virtual-frame-id/frame-table virtual-frame)))
  
negative.code:       (editor-error "cannot delete this virtual frame"))
      (let ((frame (search-previous-frame vf (virtual-frame-current vf))))
        (free-frame vf (virtual-frame-current vf))
        (switch-current-frame vf frame))
      (setf (virtual-frame-changed vf) t)))
  
  (define-key *global-keymap* "C-z p" 'frame-multiplexer-prev)
  