-/** The item \c n in symbol list \c l is \c used. */
-void symbol_list_n_used_set (symbol_list *l, int n, bool used);
-
-/** Set the \c \%destructor for \c node as \c destructor at \c loc. */
-void symbol_list_destructor_set (symbol_list *node, const char *destructor,
- location loc);
+/* Check whether the node is a border element of a rule. */
+bool symbol_list_null (symbol_list *node);