You could do something like this: ``` val list = l...

# announcements

[diesieben07]

You could do something like this:

val list = listOf("hello" to "world", "hello" to "world2", "bla" to "quz")
val result = list.groupingBy { it.first }.fold(null as String?) { acc, elem -> acc ?: elem.second }

[diesieben07]

Or, maybe better:

val list = listOf("hello" to "world", "hello" to "two worlds", "bla" to "quz")
val result = list.groupingBy { it.first }.aggregate { _, acc: String?, elem, _ -> acc ?: elem.second }

[iex]

looks good, thanks! I was thinking also using just map - similar to what you did with aggregate

[iex]

but I think I'll write an extension groupBySingle or similar to do it in one step

[diesieben07]

The nice thing about using groupingBy is that it does not construct and intermediary Map<K, List<V>> for the grouping.

[diesieben07]

It directly applies your aggregation using the source iterator.

[iex]

okay...

[diesieben07]

You can of course use groupingBy like I showed in your extension function 😉

[iex]

I thought about that, thanks!