Session management -- maintain state of logic images.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/Thy/session.ML	Wed Feb 03 17:28:40 1999 +0100
@@ -0,0 +1,56 @@
+(*  Title:      Pure/Thy/session.ML
+    ID:         $Id$
+    Author:     Markus Wenzel, TU Muenchen
+
+Session management -- maintain state of logic images.
+*)
+
+signature SESSION =
+sig
+  val path: unit -> string list
+  val welcome: unit -> string
+  val use_dir: bool -> bool -> string -> unit
+end;
+
+structure Session: SESSION =
+struct
+
+(* session state *)
+
+val session = ref ([]: string list);
+val session_path = ref ([]: string list);
+val session_finished = ref true;
+
+fun path () = ! session_path;
+
+fun add_path reset s =
+  (session := ! session @ [s]; session_path := (if reset then [] else ! session));
+
+
+(* diagnostics *)
+
+fun str_of [] = "Pure"
+  | str_of ids = space_implode "/" ids;
+
+fun welcome () = "Welcome to Isabelle/" ^ str_of (! session) ^ " (" ^ version ^ ")";
+
+
+(* init *)
+
+fun init reset name =
+  if not (! session_finished) then
+    error ("Unfinished session " ^ quote (str_of (! session)) ^ " for logic " ^ quote name)
+  else (add_path reset name; session_finished := false);
+
+
+(* finish *)
+
+fun finish () = (ThyInfo.finish_all (); session_finished := true);
+
+
+(* use_dir *)	(* FIXME info *)
+
+fun use_dir reset info name = (init reset name; Use.exit_use "ROOT.ML"; finish ());
+
+
+end;