anchor.diff:        (funcall !continuation! !level!) (undo-bindings))))
   
   (defun arg/3 (index term arg !level! !continuation!
  -              &aux (!old-trail! *trail*)
  -                   #+SYMBOLICS (!nsubgoals! '(0 nil)))
  -  #+SYMBOLICS (declare (ignore !nsubgoals!))
  +              &aux (!old-trail! *trail*))
     (incf !level!)
     (dereference term
       :if-variable  (error "ARG was given non-compound second argument ~A" term)
  
positive.code: ;; printing due to bug in DBG:FRAME-LOCAL-VALUE that causes an error if named
  ;; variable isn't found
  
  (defun call/1 (x !level! !continuation!
                 #+SYMBOLICS &aux #+SYMBOLICS (!nsubgoals! '(1 nil)))
    #+SYMBOLICS (declare (ignore !nsubgoals!))
    (incf !level!)
    (dereference x
      :if-variable (error "CALL was given non-compound argument ~A" x)
  
negative.code: 
  (defun query-success (!level!)
    (declare (ignore !level!))
    nil)
  
  (defun query (&optional variables goal &rest options)
  