suggested helper function: bindEvent

[rprije]

Hi. I've found this function quite useful. The naming reflects its similarity to monadic bind but I'm open to suggestions for alternative names:

bindEvent :: (MonadFix m, Adjustable t m, MonadHold t m)
=> m (Event t a) -> (a -> m (Event t b)) -> m (Event t b)
bindEvent first secondFun = do
rec
let becomeSecondEv = fmap secondFun firstEv
(firstEv, secondEvEv) <- runWithReplace first becomeSecondEv
switchEvent secondEvEv

where switchEvent is from reflex-frp/reflex#49:
switchEvent :: (Reflex t, MonadHold t m) => Event t (Event t a) -> m (Event t a)
switchEvent = fmap switch . hold never

I've used it for creating login widgets that behave similarly to Google's (username and password entry are two separate widgets where the second's creation is triggered by the first).

The type is convenient for creating long chains of widgets that dynamically update while carrying along the payload from previous widgets' events.

[dfordivam]

@rprije you may want to implement this in reflex using Reflex.Network APIs..