-let string_of_levels l sep =
- let entry_out (s, b, v) =
- let pos = if b then " HEAD: " else " TAIL: " in
- string_of_int v ^ pos ^ s ^ sep
- in
- let rec levels_out = function
- | [] -> ""
- | head :: tail -> entry_out head ^ levels_out tail
- in
- levels_out l
-
-