Hi! I have code like this:

fun <T> test(v: T, lambda: (T) -> Unit ) {
  lambda(v)
}

And at call site i have code :

val lambda = {v : Any -> println(v)}
test<SomeObject>(SomeObject(), lambda)

The code below wont compile, cause compiler want to have my val lambda have parameter type exact as declared in function. How should I modify my fun test declaration to allow <in Parameter> in lambda parameter?

What is

low bound

?

I mean <in Parameter>

(T) -> R

means a function, which accepts

T

and returns

R

. By this meaning,

T

is always

in

, so basically this is the same as

Function

interface in Java: it accepts one thing and returns one thing. In the example you provided

Consumer

accepts

T

and returns nothing. In Kotlin it would be

(T) -> Unit

, so as you wrote