Hi guys, is there a stdlib function to create a `Map<K, List<V>>` from a `List<Pair&l...

# announcements

[Joffrey]

Hi guys, is there a stdlib function to create a Map<K, List<V>> from a List<Pair<K,V>> ?
I'm looking for the same thing as toMap(), but instead of discarding duplicate keys, it would aggregate the values in a list.

For now, I haven't found shorter than this trivial groupBy :

fun <K, V> List<Pair<K, V>>.toMapAggregate(): Map<K, List<V>> = groupBy(
    { (k, _) -> k },
    { (_, v) -> v }
)

[karelpeeters]

val map = list.groupBy({ it.first }, { it.second })

[karelpeeters]

Ah my bad you knew that already.

[Joffrey]

Yes, but it is a bit shorter, so that's a win already 🙂 I was hoping for a stdlib function that would do that on its own, because it seems like a very common use case to me.