Hello :-) What is the new way to do something lik...

# arrow

[Mervyn McCreight]

Hello :-)

What is the new way to do something like:

val someList = ...
val someListOfIOs = someList.map { IO { ... } }
someListOfIOs.sequence(IO.applicativeError())

Now that IO is gone (and sequence is deprecated)? 🤔

Image I have a list of items, and want to do some side-effect actions for each, but want to short-circuit everything when the first fails.

[stojan]

AFIK there is a list.map function that takes a suspend function as an argument, you can use that one

[simon.vergauwen]

inline Iterable<A>.map(..): List<B> since the definition in the Kotlin Std is inline you can simply call suspend fun from inside it.

So you can simple do someList.map { suspendfun() }.

[Mervyn McCreight]

Thanks, I'll try that one. The short-circuiting here works because of how exceptions work, am I right? How would you solve this if you would not want to raise Exceptions but rather communicate errors using Either ? 🤔

[stojan]

list.map { Either.catch { suspendFun() } } then use traverseEither

[simon.vergauwen]

So list.traverseEither { Either.catch { suspendFun() } }

if you don't want to short-circuit but run all tasks, and collect the Throwable into NonEmptyList you can also do:

list.traverseValidated {
  Validated.catchNel {
    suspendFun()
  }
}