anchor.diff:       do (loop
              for acc-cell on accumulator
              for res-cell = results then (cdr res-cell) ;; Don't stop looping at
  -           ;; the end of results
  +                                                      ;; the end of results
              do (push (car res-cell) (car acc-cell)))
        finally (return (apply #'values (mapcar #'nreverse accumulator)))))
   
  
positive.code:   (loop
       for list in lists
       when (not list)
       do (return (list nil nil))
       collecting (car list) into cars
       collecting (cdr list) into cdrs
       finally (return (list cars cdrs))))
  
negative.code: of FUNC into a single list."
    (loop
       for (args rest-lists) = (unzip-lists lists) then (unzip-lists rest-lists)
       while args
       nconcing (multiple-value-list (apply func args))))
  
  
  