anchor.diff:    (w/uniq val
       `(let ,val ,x
          (if (funcall ,test ,val)
  -	   ,val
  -	   ,alt))))
  +           ,val
  +           ,alt))))
   
   (mac zap (op place &rest args)
     "Assigns the value of applying op to the rest of the args
      to the second arg"
     (mvb (vars forms var set access)
          (get-setf-expansion place)
  -    `(withs (,@(mappend #'list vars forms) ,(car var) (funcall ,op ,access ,@args))
  +    `(withs (,@(mappend #'list vars forms)
  +             ,(car var) (funcall ,op ,access ,@args))
          ,set)))
   
   (mac or= (place new)
  
positive.code:        (get-setf-expansion place)
      (w/uniq (val win)
        `(withs (,@(mappend #'list vars forms))
  	 (mvb (,val ,win) ,access
  	   (let ,(car var) (if (or ,val ,win) ,val ,new)
  	     ,set))))))
  
  (mac in (x &rest choices)
    "Checks if the result of evaluating x is the result of
  
negative.code:    ys is"
    (w/uniq y
      `(mapcan (fn (it) ; we can use mapcan because map creates new conses
                   (map (fn (,y)
                            (funcall ,f it ,y))
                        ,ys))
               ,xs)))
  