Hi All, is there any way to remove the `.k()` as m...

# arrow

[Xuc Xiem]

Hi All, is there any way to remove the .k() as much as possible in the following example:

val m = mapOf("a" to listOf(1, 2).k(), "b" to listOf(3).k()).k()
val n = mapOf("a" to listOf(4).k(), "c" to listOf(5, 6).k()).k()
val p = MapK.semigroup<String, ListK<Int>>(ListK.semigroup()).run { m + n }

[aballano]

hi there! Have you tried just removing all .k()? I believe it should work

[aballano]

hmmm actually it doesn’t output the same, but it should AFAIK, i’ll investigate 👀

[pakoito]

+ for maps in the standard library doesn't add the values together

[pakoito]

someone asked that on twitter yesterday hahaha

[aballano]

indeed, using combine works with the .k() but not for plain list and a Map. Ideally this should work

val m = mapOf("a" to listOf(1, 2), "b" to listOf(3))
val n = mapOf("a" to listOf(4), "c" to listOf(5, 6))
val p = Map.semigroup<String, List<Int>>(List.semigroup()).run { m.combine(n) }

but it seems there’s no Semigroup generated for map although it exists for list 🤔

[aballano]

maybe @pakoito knows more about this 😄

[Xuc Xiem]

Hi @aballano (or anybody), could you post the import <http://arrow.xxx|arrow.xxx> when you use standard kotlin map, list and combine? My IntelliJ suggested import arrow.core.extensions.list.semigroup.List.semigroup but there's still compilation error.

[aballano]

with the code I pasted it doesn’t work because it cannot find Map.semigroup() 😕

[aballano]

I created a bug ticket to investigate 👌 https://github.com/arrow-kt/arrow-core/issues/140 thank you @Xuc Xiem you can follow it to know when is fixed

[Xuc Xiem]

Thank you very much 🙂