Hi, Another question. I have two lists, List<A>, and List<B>, and I want to pass them th...

# arrow

[Satyam Agarwal]

Hi, Another question.
I have two lists, List<A>, and List<B>, and I want to pass them through Ior to perform actions based on if they are empty or not.
Only sensible logic I’ve been able to get to so far, is, Ior.fromNullables(Nel.fromList(list1).getOrElse { null }, Nel.fromList(list2),getOrElse { null})
This is obviously not good, as Nel<A>? effectively means List<A>, so i can just list1.isEmpty() && list2.isEmpty to cover Ior cases.
However, what I want is Nel after checking the states.
Is there something better that can be done here ?

Pattern matching on Option<Nel<A>> to Option<Nel<B>> also doesn’t work. I can’t say for example when exp is Pair<Some, None>

[simon.vergauwen]

So you want Ior<Nel<A>, Nel<B>>?
What do you expect if both are empty?

[Satyam Agarwal]

I would've hoped it’ll get covered by Ior<Nel<A>, Nel<B>>?
Then I can just check if Ior is null, then I perform operation that doesn't need any of these lists.

[Satyam Agarwal]

I can Ofcourse make an Ior for example Ior.fromlists(..) , but I thought I can ask here first.

[simon.vergauwen]

Right, I would probably go for the first option then.
This pattern can be cleaned up if you need it regularly in your downstream project.

You can use orNull() instead of getOrElse { null } though

[Satyam Agarwal]

By cleaning up the pattern, you mean, me adding some wrappers in my project to achieve it, or introducing an api in the arrow library ?

[Satyam Agarwal]

Also, thanks a lot for the answers. Always appreciate it.

[mitch]

@Satyam Agarwal i think you are looking for Option<A>.align(other: Option<B>, fn: (Ior<A, B>) -> C): Option<C>?

val first: Option<NonEmptyList<Int>> = Nel.fromList(listOf(5))
val second: Option<NonEmptyList<String>> = Nel.fromList(listOf("one"))

val result: Option<...> = first.align(second) { ior: Ior<Nel<Int>, Nel<String>> ->
    // ...
    
}

[mitch]

align will give you a Some<Ior<A, B>> if either Option<A> or Option<B> is some. it will otherwise yield None

[mitch]

If I understand the question correctly, you’d want to operate on the ior iff one / both of them is defined. In this case you can specify the lambda block after the call to align to immediately to operate on the resulting ior (like the example above) or do a map/flatMap on the option or do it within an option { } context if you’d wish to have a more complex operation, i.e.:

option { 
    val ior: Ior<NonEmptyList<A>, NonEmptyList<B>> = maybeNelA.align(maybeNelB).bind()
    // do more things here if ior is defined
}

[Satyam Agarwal]

Amazing !!!! Thank you so much !