Can anyone explain me difference between direct in...

# arrow

[genovich]

Can anyone explain me difference between direct invocation of suspend function and wrapping it into effect() inside ConcurrentSyntax?

[kioba]

my understanding is that wrapping normal suspend functions into effect removes the eager execution and will be triggered only at the end rendering the suspend function invocation lazy.
I believe that is the reason why Arrow-fx is created to allow lazy Coroutines evaluations compared to KotlinX-Coroutines library

[simon.vergauwen]

effect is a @RestrictSuspension DSL, which means that all foreign effects beside F need to explicitly wrapped in effect.

If we wouldn't do it, then we cannot guarantee that suspend functions are safely interleaved into `F`'s execution like @kioba mentioned 🙂

[simon.vergauwen]

The DSL basically prevents doing the following, whilst still allowing foreign suspend effects.

val x: IO<Unit> = io.flatMap {
  foreignSuspendFunction()
  IO { otherSupendFunction() }
}

In the above pseudo code (which could be the result without @RestrictSuspension or effect), you'd see that foreignSuspendFunction() gets executed whilst building the IO value instead of when running the IO value.

[simon.vergauwen]

However, we felt that this was not very Kotlin idiomatic which was the biggest drive to implement IO as a suspend library, which took quite a while to crack the correct encoding which offer the same guarantees as IO.