I want to split a list into parts based on a condi...

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[diesieben07]

I want to split a list into parts based on a condition. Example: Split on even numbers:

val input = listOf(4, 1, 1, 3, 2, 5, 2)
val output = input.chunkedBy { it % 2 == 0 } // should be: [[4, 1, 1, 3], [2, 5], [2]]

Is there such a thing in the standard library?

[nfrankel]

did you try groupBy()?
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/group-by.html

[diesieben07]

groupBy returns a Map though

[nfrankel]

true

[nfrankel]

but it’s then quite easy to get its values and put it into a list (or an array)

[spand]

.values or do you absolutely need a List ?

[diesieben07]

Yes, I need a list. And I also need the order preserved.

[diesieben07]

groupBy does not help me here at all, it stuffs things into a bag by a condition

[diesieben07]

I need to split based on a condition.

[nfrankel]

ok
then sorry, i don’t know the stdlib well enough to help you there

[nfrankel]

😞

[diesieben07]

That's okay

[nfrankel]

chunked() is based on size...

[nfrankel]

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/partition.html?

[nfrankel]

seems like it should work for you

[spand]

I guess fold is the closest you can get

[diesieben07]

partition only checks a boolean condition

[rrader]

condition only boolean can be

[rrader]

val input = listOf(4, 1, 1, 3, 2, 5, 2)
println(input.partition({ it % 2 == 0 }))

[diesieben07]

That does not do what I want even remotely.

[diesieben07]

It shoves all even numbers in one list and uneven ones in the other. That is not what I need.

[rrader]

but what do you need? in message you wrote "Split on even numbers"

[diesieben07]

See example input->output above...

[rrader]

and what is condition in that example?

[diesieben07]

It specifies the element to split on

[diesieben07]

Every even number should "start a new list"

[Richard Green]

What if the first n elements (n>0) are not true for the condition?

[Richard Green]

if one simplifies it to (t)rue and (f)alse, then is the output of the form (f*)(tf*)* ?

[fitzoh]

so basically a repeated takeWhile

[diesieben07]

Correct

[diesieben07]

What if the first n elements (n>0) are not true for the condition?

Then they would be in their own group. I want behavior "like String.split".

[hho]

Ugly, but seems to work: https://try.kotlinlang.org/#/UserProjects/hvruqbrvlhmdbms8mp374cj3ad/i0nf1m4h6iusd4u3d061usmk9q

[karelpeeters]

condition.invoke(it) -> condition(it)

[diesieben07]

thats exactly what I wrote for myself 😄

[diesieben07]

except i used for..in

[karelpeeters]

Out of interest, what is the use case?

[diesieben07]

Parsing a terrible XML document. I get a list of text blocks intermitted with <audio> elements. The <audio> elements specify which audio file to use for the following text blocks.

[hho]

@karelpeeters Fixed. But as I said: It's ugly.

[diesieben07]

I want to parse it into groups of audio+list of text