Sadly I've found some real basic stuff missing.

take(Int)

,

drop(Int)

...

Interesting project tho.

I'm not sure I'd extend Kotlin's

List

interface. It gives false sense of having everything there, like

map

,

associate

, etc.

For immutable collections I'd expect them to return immutable types.

I have to say it was smart from your side to use pcollections as implementation behind and first work on the API.