When programming in tagless-final style, I can sta...

# arrow

[Marcin Gryszko]

When programming in tagless-final style, I can stack Either with IO using EitherT : val M: Monad<EitherTPartialOf<MyErrorType, ForIO>> = EitherT.monad(IO.monad()) and pass the monad to functions that require monadic combinators.

What about Concurrent? I have a function calling two other effectful functions concurrently using the parMapN combinator. Both functions can return errors and I want to combine their results only if both terminated successfully:

fun <F> getActivities(
    C: Concurrent<F>,
    getAthleteActivities: () -> Kind<F, List<ApiActivity>>,
    getAthlete: () -> Kind<F, ApiAthlete>
): Kind<F, List<Activity>> = C.run {
    parMapN(dispatchers().io(), getAthleteActivities(), getAthlete()) { (apiActivities, apiAthlete) ->
        apiActivities.map { toActivity(it, apiAthlete) }
    }

Is it possible to work with abstractions (Concurrent) or do I have to use concrete types like IO<Either<A, B>>?