anchor.diff:      (my-put 'empty-termlist? '(dense) #'empty-termlist?)
       (my-put 'add-terms '(dense dense) #'(lambda (l1 l2) (tag (add-terms l1 l2))))
       (my-put 'mul-terms '(dense dense) #'(lambda (l1 l2) (tag (mul-terms l1 l2))))
  +    (my-put 'div-terms '(dense dense) #'(lambda (l1 l2)
  +					    (tag (div-terms l1 l2))))
       'done))
   (install-dense-term-list-package)
   
  
positive.code: 	    #'(lambda (p1 p2) (tag (mul-poly p1 p2))))
      (my-put 'div '(polynomial polynomial)
  	    #'(lambda (p1 p2) (tag (div-poly p1 p2))))
      ;;2.87 add =zero?
      (my-put '=zero? '(polynomial) 
  	    #'(lambda (p) (empty-termlist? (term-list p))))
  
      (my-put 'make 'polynomial
  	    #'(lambda (var terms) (tag (make-poly var terms))))
      'done))
  
  (install-polynomial-package)
  
negative.code:     (my-put 'empty-termlist? '(sparse) #'empty-termlist?)
      (my-put 'add-terms '(sparse sparse) #'(lambda (l1 l2) (tag (add-terms l1 l2))))
      (my-put 'mul-terms '(sparse sparse) #'(lambda (l1 l2) (tag (mul-terms l1 l2))))
      (my-put 'div-terms '(sparse sparse) #'(lambda (l1 l2)
  					    (tag (div-terms l1 l2))))
      'done))
  
  (install-sparse-term-list-package)
  