let rec cmp t1 t2 =
match t1, t2 with
| [], [] -> XEQ
- | _, [] -> XGT
- | [], _ -> XLT
+ | _, [] -> (* XGT *) assert false (* hd symbols were eq *)
+ | [], _ -> (* XLT *) assert false (* hd symbols were eq *)
| hd1::tl1, hd2::tl2 ->
let o = aux_ordering ~head_only hd1 hd2 in
if o = XEQ && not head_only then cmp tl1 tl2 else o