///
///Unwrap a behavior inside another behavior to give a time-varying behavior implementation.
///
public static Behavior <TA> SwitchB <TA>(Behavior <Behavior <TA> > bba)
{
Func <TA> za = () => bba.SampleNoTrans().SampleNoTrans();
var @out = new EventSink <TA>();
var h = new TransactionHandler <Behavior <TA> >();
h.Run = (trans2, ba) =>
{
// Note: If any switch takes place during a transaction, then the
// value().listen will always cause a sample to be fetched from the
// one we just switched to. The caller will be fetching our output
// using value().listen, and value() throws away all firings except
// for the last one. Therefore, anything from the old input behaviour
// that might have happened during this transaction will be suppressed.
if (h.CurrentListener != null)
{
h.CurrentListener.Unlisten();
}
h.CurrentListener = ba.Value(trans2).Listen(
@out.Node,
trans2,
new TransactionHandler <TA>
{
Run = (trans3, a) => @out.Send(trans3, a)
},
false);
};
Listener l1 = bba.Value().Listen_(@out.Node, h);
return(@out.AddCleanup(l1).HoldLazy(za));
}
/// <summary>
/// Unwrap a behavior inside another behavior to give a time-varying behavior implementation.
/// </summary>
/// <typeparam name="T">The type of the behavior.</typeparam>
/// <param name="bba">The behavior containing another behavior.</param>
/// <returns>The unwrapped behavior.</returns>
public static Behavior <T> SwitchC <T>(this Behavior <Behavior <T> > bba)
{
return(Transaction.Apply(
trans1 =>
{
Lazy <T> za = bba.SampleLazy().Map(ba => ba.Sample());
Stream <T> @out = new Stream <T>(bba.KeepListenersAlive);
MutableListener currentListener = new MutableListener();
void H(Transaction trans2, Behavior <T> ba)
{
currentListener.Unlisten();
currentListener.SetListener(ba.Value(trans2).Listen(@out.Node, trans2, @out.Send, false));
}
IListener l1 = bba.Value(trans1).Listen(@out.Node, trans1, H, false);
return @out.UnsafeAttachListener(l1).UnsafeAttachListener(currentListener).HoldLazyInternal(trans1, za);
},
false));
}
/// <summary> /// A stream that is guaranteed to fire once upon listening, giving the current /// value of a behavior, and thereafter gives the updates/steps for the behavior. /// </summary> /// <typeparam name="T">The type of the values in the behavior.</typeparam> /// <param name="b"></param> /// <returns></returns> /// <remarks> /// This is an OPERATIONAL primitive, which is not part of the main Sodium /// API. It breaks the property of non-detectability of behavior steps/updates. /// The rule with this primitive is that you should only use it in functions /// that do not allow the caller to detect the behavior updates. /// </remarks> public static Stream <T> Value <T>(Behavior <T> b) => Transaction.Apply((trans, _) => b.Value(trans), false);