src/Pure/Concurrent/unsynchronized.ML

+(*  Title:      Pure/Concurrent/unsynchronized.ML
+    Author:     Makarius
+
+Raw ML references as unsynchronized state variables.
+*)
+
+structure Unsynchronized =
+struct
+
+datatype ref = datatype ref;
+
+val op := = op :=;
+val ! = !;
+
+fun change r f = r := f (! r);
+fun change_result r f = let val (x, y) = f (! r) in r := y; x end;
+
+fun inc i = (i := ! i + (1: int); ! i);
+fun dec i = (i := ! i - (1: int); ! i);
+
+fun setmp flag value f x =
+  uninterruptible (fn restore_attributes => fn () =>
+    let
+      val orig_value = ! flag;
+      val _ = flag := value;
+      val result = Exn.capture (restore_attributes f) x;
+      val _ = flag := orig_value;
+    in Exn.release result end) ();
+
+end;