+let set_sort h s =
+ H.add sort h s; succ h
+
+let graph_of_string err f s =
+ try
+ let x = S.sscanf s "Z%u" C.start in
+ if x > 0 then f (s, fun h -> x + h) else err ()
+ with
+ S.Scan_failure _ | Failure _ | End_of_file -> err ()
+
+let graph = ref (graph_of_string C.err C.start default_graph)