Hey, :arrow: and functional guys, just a question....

# arrow

[Riccardo Cardin]

Hey, arrow and functional guys, just a question. Following this article, in Kotlin, we can compare the features of the IO[A] monad defined in Scala with a suspend () -> A function. This is true because Kotlin translates the previous suspend function into code using continuations, and it’s guaranteed to return a Result[A].

Let’s introduce the Either[E, A] into the equation. We can have a suspend () -> Either[E, A] (or a suspend Raise<E>.() -> A as well). The Kotlin compiler will translate such a function into a function using continuations, ending with the type Result[Either[E, A]].

So, a suspend () -> Either[E, A] is equivalent to the blueprint of a function that can make side effects (the suspend part) and ends with a Failure(Throwable) in case of unexpected problems/bugs, with a Left[E] in case of handled errors, with a Right[A] in case of the happy path occurs.

In some way, it’s very similar to the IO[E, A] defined in the ZIO library.

Is it correct? Thanks a lot gratitude thank you

[raulraja]

I think all your assumptions are correct. Some of the differences between suspend and IO are a bit more nuance at the implementation level. For example stack safety, implicit safe resource handling, scheduler fairness, etc. suspend and IO follow different strategies and decissions on those.
Having said that, most of those can be considered implementation details but at the end suspend () -> A is the kotlin equivalent to IO[A] in other langs and libraries and the main reason why we got rid of IO<A> in Arrow in favor of suspend.