| Fin i -> string_of_int i
| Ref (k, i) -> "-" ^ P.string_of_mark k ^ "-" ^ string_of_int i
| Unk -> "-" ^ P.string_of_mark k
| Fin i -> string_of_int i
| Ref (k, i) -> "-" ^ P.string_of_mark k ^ "-" ^ string_of_int i
| Unk -> "-" ^ P.string_of_mark k