adam@15: con t a = {Source : source a,
adam@15:            OnSet : source (a -> transaction {})}
kkallio@14: 
adam@15: fun create [a] (i : a) =
adam@15:     s <- source i;
adam@15:     f <- source (fn _ => return ());
kkallio@14: 
adam@15:     return {Source = s,
adam@15:             OnSet = f}
kkallio@14: 
adam@15: fun onChange [a] (t : t a) f =
adam@15:     old <- get t.OnSet;
adam@15:     set t.OnSet (fn x => (old x; f x))
kkallio@14: 
adam@15: fun set [a] (t : t a) (v : a) =
adam@15:     Basis.set t.Source v;
adam@15:     f <- get t.OnSet;
adam@15:     f v
kkallio@14: 
adam@15: fun get [a] (t : t a) = Basis.get t.Source
kkallio@14: 
adam@15: fun value [a] (t : t a) = signal t.Source