+let string_of_entry = function
+ | `About `Blank -> "about:blank"
+ | `About `Current_proof -> "about:proof"
+ | `About `Us -> "about:us"
+ | `Check _ -> "check:"
+ | `Cic (_, _) -> "term:"
+ | `Dir uri -> uri
+ | `Uri uri -> UriManager.string_of_uri uri
+ | `Whelp (query, _) -> query
+
+let entry_of_string = function
+ | "about:blank" -> `About `Blank
+ | "about:proof" -> `About `Current_proof
+ | "about:us" -> `About `Us
+ | _ -> (* only about entries supported ATM *)
+ raise (Invalid_argument "entry_of_string")
+