Good tutorial for functional programming in Kotlin?

A colleague of mine struggles with functional programming and I want to give him something to learn. Is there a good tutorial about basics like filter, map, reduce and some functional programming basics along the line?

it’s not a good way to start functional programming in Kotlin, the good way is to start from a functional language, not a Multiparadigm language like Kotlin.

First step: you have to try to learn functional data structures

and then you can start to learn a functional language like(Haskell, lisp, Clojure(recommended), …)
this’s a good resource to learn Clojure

finally, you can read Kotlin Documents

I hope more books are written about FP in Kotlin