anchor.diff:     "FLATTEN" "LIST-TRIM" "TRANSPOSE" "AGET" "MEMQ"
      "MAP-CARTESIAN-PRODUCT"
      "PLIST-KEYS" "PLIST-REMOVE" "PLIST-GET"
  -   "PLIST-PUT" "PLIST-CLEANUP" "HASHED-INTERSECTION" 
  +   "PLIST-PUT" "PLIST-CLEANUP" "HASHED-INTERSECTION"
      ;; "HASHED-REMOVE-DUPLICATES" moved to COM.INFORMATIMAGO.COMMON-LISP.CESARUM.SEQUENCE
      "ENSURE-LIST" "PROPER-LIST-P" "LIST-LENGTHS" "LIST-ELEMENTS"
      "ENSURE-CIRCULAR" "MAKE-CIRCULAR-LIST" "CIRCULAR-LENGTH"
  
positive.code: RETURN:  (elt args 0) x (elt args 1) x ... x (elt args (1- (length args)))
           = the set of tuples built taking one item in order from each list
             in args.
  EXAMPLE: (COMBINE '(WWW FTP) '(EXA) '(COM ORG))) 
             --> ((WWW EXA COM) (WWW EXA ORG) (FTP EXA COM) (FTP EXA ORG))
  "
    (cond
  
negative.code:     :collect (loop
                 :for index :from 0 :below card
                 :for item :in set
                 :nconc (if (logbitp index indicator) (list item) nil)
                 :into result
                 :finally (return result)) :into result
      :finally (return result)))
  
  