src/Pure/ML-Systems/unsynchronized.ML

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/ML-Systems/unsynchronized.ML	Tue Sep 29 11:48:32 2009 +0200
@@ -0,0 +1,25 @@
+(*  Title:      Pure/ML-Systems/unsynchronized.ML
+    Author:     Makarius
+
+Raw ML references as unsynchronized state variables.
+*)
+
+structure Unsynchronized =
+struct
+
+datatype ref = datatype ref;
+
+val op := = op :=;
+val ! = !;
+
+fun set flag = (flag := true; true);
+fun reset flag = (flag := false; false);
+fun toggle flag = (flag := not (! flag); ! flag);
+
+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);
+
+end;