<@U4UGS5FC7> or <@U0B8UEMV1> After this bug ( <htt...

# arrow

[streetsofboston]

@raulraja or @pakoito
After this bug ( https://github.com/arrow-kt/arrow/issues/1295 ) is fixed, will the fx { ... } calls themselves be blocking or suspending?

Looking at the Arrow code, the fx { ... } calls return a returnedMonad immediately (which could cause that #1295 bug). If this is fixed and its suspending lambda does not continue immediately, will the fx call be blocking or suspending to get the correct monad to be returned by it?

I’m asking this especially for the fx calls returning Either, Try, etc values.

[raulraja]

With the latest Fx changes it will be all suspended and you don't need to use io or anything

[raulraja]

You are fine using suspend and returning either

[raulraja]

All combinators will be available globally without type class dependencies

[raulraja]

Just suspend function composition

[raulraja]

You can choose to run on arrow or coroutines core runBlocking and launch

[raulraja]

On arrow you would use the unsafe runners

[streetsofboston]

As an example:

override suspend fun getReverse(latitude: Double, longitude: Double): Either<GeoError, String> {
        val tryCity: Try<String> = fx {
            val reverse = effect { service.getReverse(GeoLocation(latitude, longitude)).await() }
            (!reverse).city.orEmpty()
        }

        return tryCity.toEither { it.asGeoError }
    }

The getReverse method here must be suspend after the fix, because fx will be suspending as well, correct?

[raulraja]

That is the either fx

[raulraja]

I'm talking about using as IO

[raulraja]

You can I stantiate the try outside of it's fx

[raulraja]

The try constructor works in the environment not suspended

[raulraja]

The use the Fx block to compose

[streetsofboston]

But service.getReverse(....).await() is suspending (Deffered.await)

[streetsofboston]

Ah.. you mean not use fx at all here, because I’m just creating one Either (or Try).

Use fx here only if I would’ve had a bunch of service calls returning Either values, to easily combine/compose these multiple Either values into one value then returned by the call to fx. Is this correct?

[streetsofboston]

override suspend fun getReverse(latitude: Double, longitude: Double): Either<GeoError, String> {
        return try {
            service.getReverse(GeoLocation(latitude, longitude)).await()
                .city
                .orEmpty()
                .just()
        } catch (e: Throwable) {
            e.asGeoError
                .raiseError()
        }
    }

[streetsofboston]

I’m still struggling to figure out when to use fx { ... } returning a value (Either, Try, etc) or when to just use a plain call to a suspend function (inside the body of a suspend function) 🙂

[raulraja]

in the new version of fx when you deal with things like this is which is io fx actually returns a suspended function

[raulraja]

so you are fine staying in suspend land

[raulraja]

you will be able to use attempt, handleErrorWith etc... in those as well