src/Tools/Compute_Oracle/am_ghc.ML

 	fold_rev add_rule rules Inttab.empty
     end
 
 fun haskell_prog name rules = 
     let
-	val buffer = ref ""
+	val buffer = Unsynchronized.ref ""
 	fun write s = (buffer := (!buffer)^s)
 	fun writeln s = (write s; write "\n")
 	fun writelist [] = ()
 	  | writelist (s::ss) = (writeln s; writelist ss)
 	fun str i = Int.toString i

 	val _ = map list_group constants
     in
 	(arity, !buffer)
     end
 
-val guid_counter = ref 0
+val guid_counter = Unsynchronized.ref 0
 fun get_guid () = 
     let
 	val c = !guid_counter
 	val _ = guid_counter := !guid_counter + 1
     in

 fun tmp_file s = Path.implode (Path.expand (File.tmp_path (Path.make [s])));
 fun wrap s = "\""^s^"\""
 
 fun writeTextFile name s = File.write (Path.explode name) s
     
-val ghc = ref (case getenv "GHC_PATH" of "" => "ghc" | s => s)
+val ghc = Unsynchronized.ref (case getenv "GHC_PATH" of "" => "ghc" | s => s)
 
 fun fileExists name = ((OS.FileSys.fileSize name; true) handle OS.SysErr _ => false)
 
 fun compile cache_patterns const_arity eqs = 
     let