fun foo(): KSuspendFunction1<>

could also work.

I use only lambda syntax for all functional type, including suspend, same way as for other cases instead of FunctionN interfaces

I prefer the lambda notation, not the KFunction, etc ones

My problem with that is if anyone unused to this notation looks at the code it’s a little bit difficult to know what to search online for in order to understand what’s happening.

True. When folks learn Kotlin, or when you teach Kotlin, it is important to show how higher order functions work and how they look. It’s one of the first things to tackle.

I don’t like to go on the assumption that a developer underwent a full Kotlin course before touching my code. Especially not with the large amount of “if you can code Java you can code Kotlin” statements out there, which gives some people the impression that they don’t have to read up about everything.

That is why i think it is important to visit the topic of lambdas/higher-order functions rather sooner than later and consider it part of the ‘basics’. And Kotlin is a different language. Nothing wrong with learning new one, even it is just the basics 🙂

Definitely, but I’m not the one who needs to be convinced here. The issue is that I know for a fact people who know even less than me will work on my code in the future.

That is indeed something to consider. And that is why we at our company (we create apps for clients) carefully choose whether to use Java or Kotlin. But once the choice is made, we strive to write in the language as idiomatic as possible. In this example, it would mean to favor

() -> Any

over

KFunction1

for example 🙂

🤔

To me

KFunction1

is an implementation artifact of the lambda implementation. E.g. Haskell has no separate type/syntax for lambdas; I don't think Scala does, either (although I am less sure of this).

Yup. Lambdas and higher-order functions and extension functions are part of the core kotlin knowledge (and a few other things). But things such as coroutines, (property) delegates, etc are more advanced

Also I think that the

K*Function*

types are jvm-specific, so you can’t use them from common modules in multiplatform projects