src/Pure/PIDE/document.ML

--- a/src/Pure/PIDE/document.ML	Wed Aug 11 18:44:06 2010 +0200
+++ b/src/Pure/PIDE/document.ML	Wed Aug 11 22:41:26 2010 +0200
@@ -7,10 +7,12 @@
 
 signature DOCUMENT =
 sig
-  type state_id = string
-  type command_id = string
-  type version_id = string
-  val no_id: string
+  type state_id = int
+  type command_id = int
+  type version_id = int
+  val no_id: int
+  val parse_id: string -> int
+  val print_id: int -> string
   type edit = string * ((command_id * command_id option) list) option
 end;
 
@@ -19,11 +21,18 @@
 
 (* unique identifiers *)
 
-type state_id = string;
-type command_id = string;
-type version_id = string;
+type state_id = int;
+type command_id = int;
+type version_id = int;
+
+val no_id = 0;
 
-val no_id = "";
+fun parse_id s =
+  (case Int.fromString s of
+    SOME i => i
+  | NONE => raise Fail ("Bad id: " ^ quote s));
+
+val print_id = signed_string_of_int;
 
 
 (* edits *)