is there a function to split a collection into two sub collections by a predicate? ```val unsInfos =...

# getting-started

[elect]

is there a function to split a collection into two sub collections by a predicate?

val unsInfos = intTypeInfo.filter { it.type[0] == 'U' }
val signInfos = intTypeInfo.filter { it.type[0] != 'U' }

ie

val (unsInfos, signInfos) = intTypeInfo.x { it.type[0] == 'U' }

[elect]

..partition!

[Russell Stewart]

I was just about to say that. 🙂

[elect]

I was searching by split or divide, then by defining the type, at the end I managed to find the answer on Google

[Russell Stewart]

Yeah, that can sometimes be the hardest part about finding what you're looking for. There are so many synonyms for most actions, it's hard to find the right one.

[elect]

Destructuring declarations are only allowed for local variables/values

😕

[Russell Stewart]

Is there a reason you index type in the scope where you're filtering/partitioning? Is type a sub-array in the object?

[elect]

it's a list of numeric types

val intTypeInfo = listOf(
    TypeInfo("Byte", "b"),

where

data class TypeInfo(val type: String, val extension: String)

[elect]

a quick way to filter out unsigned types and viceversa

[Russell Stewart]

OK, I see.

[Russell Stewart]

I'm not sure what that "Destructuring declarations" message is about. Is that a compiler error the IDE is giving you? How are you declaring intTypeInfo?

[elect]

you cant val (unsInfos, signInfos) at top level

[Russell Stewart]

Oh, I see. This isn't inside of a function?

[elect]

no

[Russell Stewart]

OK

[Russell Stewart]

You might be able to declare unsInfo and signInfos as vals at the top level, then do your partition call in the init block.

[elect]

it's all top level, I don't have an init

[Russell Stewart]

Oh, OK.

[Russell Stewart]

Maybe make it an extension function on List<TypeInfo>?

[elect]

I'm gonna bite the bullet and duplicate code as the first snippet

[Russell Stewart]

OK

[Klitos Kyriacou]

To avoid iterating your list twice, if you don't mind polluting the current file, you can do:

private val pair = ...partition(...)
val unsInfos = pair.first
val signInfos = pair.second

[ephemient]

(also holding onto the pair object for as long as the object lives)