(* an universe that does nothing: i.e. no constraints are kept, no merges.. *)
val oblivion_ugraph: universe_graph
+(* one of the previous two, no set to empty_ugraph *)
+val default_ugraph: universe_graph
+
+
(*
These are the real functions to add eq/ge/gt constraints
to the passed graph, returning an updated graph or raising
val add_gt:
universe -> universe -> universe_graph -> universe_graph
-val do_rank: universe_graph -> unit
+val do_rank: universe_graph -> int list * universe list
val get_rank: universe -> int
(*