;;;
;;; difference list types
;;;

*dlist* := *top* &
[ LIST *list*,
  LAST *list* ].

*null-dlist* := *dlist* &
[ LIST #last,
  LAST #last ].

*ne-dlist* := *dlist* &
[LIST *ne-list* ].

;;;
;;; types for node labels used in tree display
;;;

label :=  syn-struc &
[ LABEL-NAME string ].