anchor.diff:  (defun cgen-parenthesize (parent child)
     ;(format t "~&parent: ~A:~D" parent (precedence parent))
     ;(format t "~&child: ~A:~D" child (precedence child))
  -  (if (< (precedence child) (precedence parent))
  +  (if (> (precedence child) (precedence parent))
         (rope-parenthesize child)
         (rope child)))
   
  
positive.code: (defun precedence (e)
    (etypecase e
      (cgen-op (op-precedence (cgen-op-op e)))
      (number 99)
      (rope 99)))
  
  (defun cgen-op-symbol (op)
    "Return the canonical symbol of op"
  
negative.code:                (^= . 14)
                 (\|= . 14)
  
                 (|,| . 14)
  
                 ))))
    (defun op-precedence (op)
      (if-let ((p (gethash op hash)))
  