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kotlinlang

hello folks,

i am currently trying to learn more about functional programming using arrow. Right now i am using the Scala Exercises from here <https://www.scala-exercises.org/cats/monad> and try to implement them using arrow. Here I ran into a problem. Hope someone can help me here.

looking at the third example of the first Monad exercise:
```
List(List(1), List(2, 3)).flatten should be(
List(1,2,3)
)
```

my Kotlin/Arrow version looks like this (part of a KotlinTest):
```
import arrow.core.extensions.list.monad.flatten

...
"flatten" {
            listOf(listOf(1), listOf(2, 3)).flatten() shouldBe listOf(1, 2, 3)
}
```

However this causes an StackOverflowError:
```
java.lang.StackOverflowError
	at arrow.core.extensions.list.monad.ListKMonadKt.flatten(ListKMonad.kt:76)
	at arrow.core.extensions.list.monad.ListKMonadKt.flatten(ListKMonad.kt:76)
	at arrow.core.extensions.list.monad.ListKMonadKt.flatten(ListKMonad.kt:76)

```

When i use the _flatten()_ extension function from the kotlin stdlib my test works. This made me wonder wether this might be an issue within arrow or if i am misusing arrow here.

thanks in advance, Alphonse