let compare t1 t2 = match t1, t2 with | Tabstract s1, Tabstract s2 -> Hstring.compare s1 s2 | Tabstract _, _ -> -1 | _ , Tabstract _ -> 1 | Tsum (s1, _), Tsum(s2, _) -> Hstring.compare s1 s2 | Tsum _, _ -> -1 | _ , Tsum _ -> 1 | t1, t2 -> Pervasives.compare t1 t2