| T.Elim _ :: _ -> assert false
| T.Cut _ :: _ -> assert false
-and xls frm ls =
- let map l = F.fprintf frm "{%a}" xl l in
- List.iter map (List.rev ls)
+and xls frm = function
+ | [] -> F.fprintf frm "{}"
+ | ls ->
+ let map l = F.fprintf frm "{%a}" xl l in
+ List.iter map (List.rev ls)
in
F.fprintf frm "%a@\n" xl l