What is the advantage of using `either` over `eith...

# arrow

[Lukasz Kalnik]

What is the advantage of using either over either.eager for suspending computations?
If I use either.eager, will it simply block the current thread?

suspend fun doSomethingLong(): Either<Error, Unit>

either.eager {
    doSomethingLong() // does it block the current thread?
}

[Sam]

Does that even compile?

[Lukasz Kalnik]

Yes

[Lukasz Kalnik]

public final inline fun <E, A> eager(
    crossinline f: suspend EagerEffectScope<E>.() → A
): Either<E, A>

[simon.vergauwen]

That should not compile

[simon.vergauwen]

EagerEffectScope is marked @RestrictSuspension

[Lukasz Kalnik]

It compiles at least inside of another suspend function, maybe that's the catch

[simon.vergauwen]

Ah yes. It’s inline so it uses the suspend fro the outer scope.

[Lukasz Kalnik]

Ah ok

[Lukasz Kalnik]

Thanks!

[Lukasz Kalnik]

That explains it.

[simon.vergauwen]

Hmm.. It’s not compiling for me though 🤯

[simon.vergauwen]

Where is your suspend call?

[simon.vergauwen]

There is no suspend call inside eager in your screenshot

[simon.vergauwen]

Only the call to bind but that should be coming from eager

[Lukasz Kalnik]

So the IDE shows bind() as the suspend function...

[simon.vergauwen]

Yes, but that is coming from EagerEffectScope so it’s allowed

[simon.vergauwen]

delay(100) should not be allowed

[Lukasz Kalnik]

Makes sense, I just misinterpreted the "suspend" marker in the gutter

[Lukasz Kalnik]

Thanks for the explanation!

[Lukasz Kalnik]

Ok, so in this case, is there a difference if I use either or either.eager? I suppose not.
Or is there a reason why I should use either, e.g. because my outer function is suspending anyway?

[simon.vergauwen]

In this case there is no difference at all. You’re free to use both.