///
///Sample the behavior at the time of the event firing. Note that the 'current value'
/// of the behavior that's sampled is the value as at the start of the transaction
/// before any state changes of the current transaction are applied through 'hold's.
///
public Event <TC> Snapshot <TB, TC>(Behavior <TB> b, Func <TA, TB, TC> f)
{
Event <TA> ev = this;
var @out = new EventSink <TC>
{
SampleNow = () =>
{
Object[] oi = ev.SampleNow();
if (oi != null)
{
var oo = new Object[oi.Length];
for (int i = 0; i < oo.Length; i++)
{
oo[i] = f((TA)oi[i], b.SampleNoTrans());
}
return(oo);
}
return(null);
}
};
Listener l = Listen_(
@out.Node,
new TransactionHandler <TA>
{
Run = (trans2, a) => @out.Send(trans2, f(a, b.SampleNoTrans()))
});
return(@out.AddCleanup(l));
}
///
///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));
}
private static Event <TA> SwitchE <TA>(Transaction trans1, Behavior <Event <TA> > bea)
{
var @out = new EventSink <TA>();
var h2 = new TransactionHandler <TA>
{
Run = (trans2, a) => @out.Send(trans2, a)
};
var h1 = new TransactionHandler <Event <TA> > {
CurrentListener = bea.SampleNoTrans().Listen(@out.Node, trans1, h2, false)
};
h1.Run = (trans2, ea) => trans2.Last(
new Runnable
{
Run = () =>
{
if (h1.CurrentListener != null)
{
h1.CurrentListener.Unlisten();
}
h1.CurrentListener = ea.Listen(@out.Node, trans2, h2, true);
}
});
Listener l1 = bea.Updates().Listen(@out.Node, trans1, h1, false);
return(@out.AddCleanup(l1));
}
///
///Apply a value inside a behavior to a function inside a behavior. This is the
///primitive for all function lifting.
///
public static Behavior <TB> Apply <TA, TB>(Behavior <Func <TA, TB> > bf, Behavior <TA> ba)
{
var @out = new EventSink <TB>();
var h = new Handler <Transaction>
{
Fired = false
};
h.Run = trans1 =>
{
if (h.Fired)
{
return;
}
h.Fired = true;
trans1.Prioritized(
@out.Node,
new Handler <Transaction>
{
Run = trans2 =>
{
@out.Send(trans2, bf.NewValue()(ba.NewValue()));
h.Fired = false;
}
});
};
Listener l1 = bf.Updates().Listen_(@out.Node, new TransactionHandler <Func <TA, TB> >
{
Run = (trans1, f) => h.Run(trans1)
});
Listener l2 = ba.Updates().Listen_(@out.Node, new TransactionHandler <TA>
{
Run = (trans1, a) => h.Run(trans1)
});
return(@out.AddCleanup(l1).AddCleanup(l2).HoldLazy(() => bf.SampleNoTrans()(ba.SampleNoTrans())));
}