Both `reflex`[1] and `frpnow`[2] provide Monad instance for behavior.
AFAIK only `reactive-banana` and arrowized FRP libraries don't have it.
[1]
https://github.com/reflex-frp/reflex/blob/develop/src/Reflex/Class.hs#L598
[2]
https://hackage.haskell.org/package/frpnow-0.18/docs/Control-FRPNow-Core.htm...
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2018-01-20 19:00 GMT+05:00 martin
Hello all,
it appears to be difficult to define a Monad instance for Behavior and in many (if not all) reactive libraries Behavior is not a Monad. Why is that so?
If a Beahvior is conceptionally a function from Time to something,
newtype Behavior a = Behavior (Time -> a)
then its Monad instance should work like a Reader Monad.
Alternatively one can look at the join function
join :: Behavior (Behavior a) -> Behavior a.
This corresponds to the situation where you switch between Channels on a TV remote controle and each Channel is a behavior of Image. Then
join Behavior (Behavior image)
should give you the video stream you see on the screen. How can one possibly live without this operation?
I assume this has something to do with the actual implementation and not so much with the semantics, because semantically I don't see any problems.
So, - why is Behavior not a Monad and - how would you express the TV-remote example without a Monad?
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