(atomic) event switching on behavour values about reactive-banana HOT 3 CLOSED

As mentioned in my response to issue #17, everything is sun and rainbows concerning the semantics of reactive-banana. :-)

The main point is that rightEvent happens simultaneously with initialEvent, there is no time in between where the behavior could change. At least, that's the illusion that reactive-banana will enforce.

The obvious implementations are all correct

(leftEvent, rightEvent) = pair $ behavior <@> initialEvent

pair :: Event (Either a b) -> (Event a, Event b)
pair e = (filterLeft e, filterRight e)
    where
    filterLeft  = fmap fromLeft  . filteE isLeft 
    filterRight = fmap fromRight . filteE isRight

Note that since e is shared in the second function, the value of type Either a b will be computed only once. The only thing that happens twice is the test whether it's a Left or Right constructor. Not optimal but I think it's ok.

I do agree that partial functions like fromLeft are somewhat unsightly. Fortunately, they can all be removed by using the filterJust function mentioned in issue #17.

filterLeft = filterJust . fmap matchLeft
    where
    matchLeft (Left x) = Just x
    matchLeft _        = Nothing

That's another reason to add filterJust to the API.

from reactive-banana.

Nifty! Thank you very much for the prompt response. :-)

P.S.: You can close the issue anytime you want, or leave it open as a reminder to add some of the functions we discussed to the API.

from reactive-banana.

Ok. I have now added the filterJust function to the API.

from reactive-banana.