fromPoll behaviors are not updated before events about reactive-banana HOT 3 CLOSED

Actually, this behavior is correct!

The subtle point is the meaning of "the Behavior will be updated" and the semantics of stepper. "Updating" a behavior at time t0 means that for times t > t0, the behavior will return the new value. However, at the time t0 itself, the behavior will still return the old value, so bRef <@ e will tag the event with the value of the behavior just before the update.

A pure manifestation of this phenomenon is the following: given an event e, the events stepper 0 e <@ e and e will not be equal.

The underlying reason for these semantics is to allow recursion between events and behaviors. See also

• Handling mutually recursive GUI widgets with reactive-banana
• Can reactive-banana handle cycles in the network?

To observe the new values of the behavior, you have to use the changes function.

e2 <- changes bRef
reactimate $ print <$> e2

However, note that this combinator only works in special circumstances, essentially only when you feed its result more or less directly into reactimate.

from reactive-banana.

Thank you for your reply! That clears up the issue.

I'm closing this since it was not actually a bug.

from reactive-banana.

Thanks for reporting anyway. :-)

from reactive-banana.