--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sourceL.ur	Sun Aug 07 14:38:52 2011 -0400
@@ -0,0 +1,22 @@
+con t a = {Source : source a,
+           OnSet : source (a -> transaction {})}
+
+fun create [a] (i : a) =
+    s <- source i;
+    f <- source (fn _ => return ());
+
+    return {Source = s,
+            OnSet = f}
+
+fun onChange [a] (t : t a) f =
+    old <- get t.OnSet;
+    set t.OnSet (fn x => (old x; f x))
+
+fun set [a] (t : t a) (v : a) =
+    Basis.set t.Source v;
+    f <- get t.OnSet;
+    f v
+
+fun get [a] (t : t a) = Basis.get t.Source
+
+fun value [a] (t : t a) = signal t.Source