adam@1: datatype readiness a = Ready of a | Waiting | Invalid of string
adam@1: datatype rpcResult a = Success of a | Failure of string
adam@1: 
adam@1: fun warning [a] (s : signal (readiness a)) =
adam@1:     <xml><dyn signal={v <- s;
adam@1:                       return (case v of
adam@1:                                   Invalid s => <xml><b>{[s]}</b></xml>
adam@1:                                 | _ => <xml/>)}/></xml>