structure MsgTypes = struct
+datatype query =
+ QApt of string
+ (* Is this apt package installed? *)
+
datatype msg =
MsgOk
(* Your request was processed successfully. *)
(* Change a DBMS user's password *)
| MsgShutdown
(* Halt the server *)
+ | MsgYes
+ | MsgNo
+ (* Answers to boolean queries *)
+ | MsgQuery of query
+ (* Ask for host-specific information *)
end