``` val closure = a Int gt Int gt a 2 ``` kotlinlang #announcements

05/16/2019, 7:36 PM

val closure = { (a: Int -> Int) ->
    a * 2
}

05/16/2019, 7:37 PM

You can't. You can specify the type of

closure

explicitly though, and the IDE can even do that for you with an intention (alt/option + enter)

05/16/2019, 7:38 PM

😕 type inference is failing

05/16/2019, 7:38 PM

? Can you tell more details?

05/16/2019, 7:39 PM

val closure: (Int) -> Int = { a -> a * 2 }

is the closest you can get to what you’re asking for, I think

05/16/2019, 7:39 PM

Expected type is one way. You can also use anonymous function literal instead:

val closure = fun(a: Int): Int { ... }

streetsofboston

05/16/2019, 7:40 PM

@iex What is the type of

closure

if you would provide it explicitly?

You could end your last expression in your lambda with `as MyReturnType`….

val closure = { a: Int -> (a + 5) as Number }

Is this what you try to accomplish?

05/16/2019, 7:46 PM

yeah but I prefer to avoid casting, even in this case

managed to solve it with an extension function

streetsofboston

05/16/2019, 7:47 PM

Now i’m curious … 🙂

05/16/2019, 7:47 PM

it's a bit too custom to post it I think...

declaring a local variable with the correct type and returning it also solved it, but that was 2 lines of code 😄

streetsofboston

05/16/2019, 7:48 PM

Providing the type explicitly is probably less typing … 🙂

05/16/2019, 7:49 PM

that's basically what I'm doing with the extension

have a chain of map and flatmap which seemed to confuse the compiler

streetsofboston

05/16/2019, 7:51 PM

It could be that the new type inference system, that is still a bit in flux, may help with that.

https://www.youtube.com/watch?v=MyljSWm0Y_k▾

(fast forward to the type inference section)

05/16/2019, 7:53 PM

thanks, will watch it later 👍