Why does actually Kotlin lacks extension functions (like

apply

or

let

) which return

Unit

? Something like

fun <T> T.end(block: T.() -> Unit): Unit

When would you like to use those over the

let

or

apply

?

fun returnsUnit() = doSomething.end { ... }

Instead of

fun returnsUnit() {
  doSomething.apply { ... }
}

I think it will make situation with scoped functions even worse (there are a lot of blog posts with explanation of let/apply/run)

I've been sorta wondering about this as well. For those cases where I don't care about the return value, then I don't know whether to use

apply

or

run

as I could essentially use either. 😛

@gildor Un contraire, it makes it more expressive -

end

in the end of an evaluation chain signalizes right away that the function doesn't return anything, moreover, such chains are more straightforward and are subjects to be lazified, if it's needed. But the best reason for such a question of me is still the same - there are a lot of cases when a function contains a single operator, which could be turned into single-line expression if only there was something like

end

. Quick example - Glide's chains

Yes, but block body without return type looks much more expressive for me and easy to read

Expression bodies is also a great instrument to get rid of syntax mistakes, coming from curly braces, and lack of curly braces almost always imrpoves readability after all. Take any language where there are no curly braces at all, for example, Python (I really don't like it, but it is way one of the best examples of a good syntax). And again, functions like

fun reloadImage() {
  Glide.load(cachedUrl)
    .asDrawable()
    .apply(...)
    .apply {
      ...
    }
}

Does not seem to be really expressive and laconic, as Kotlin was intended to be

well you can always append a

asUnit()

or something like that to throw away the returned value in case you really want to use an expression

The main reason why I think block body for unit functions is better is it always clear for me that this is side effect function and returns unit if I see block body and no return type, all other ways to do that, such as proposed

end

or

asUnit

still require more focus to understand

Fair enough. Personally, I have that weird urge to try to use expressions whenever I can. Must be something psychological 😉