Здравствуйте, Serginio1, Вы писали:

S>Кстати а, что в котлине интереснее по сравнению с C#9 ?

Там есть много хороших фич, конечно, и я назову не главные. Но меня прёт от синтаксиса лямбд для некоторых частых частных случаев.

it: implicit name of a single parameter
It's very common that a lambda expression has only one parameter.
If the compiler can figure the signature out itself, it is allowed not to declare the only parameter and omit ->. The parameter will be implicitly declared under the name it:

ints.filter { it > 0 } // this literal is of type '(it: Int) -> Boolean'

— https://kotlinlang.org/docs/reference/lambdas.html#it-implicit-name-of-a-single-parameter

Passing trailing lambdas
In Kotlin, there is a convention: if the last parameter of a function is a function, then a lambda expression passed as the corresponding argument can be placed outside the parentheses:

val product = items.fold(1) { acc, e -> acc * e }

Such syntax is also known as trailing lambda.
If the lambda is the only argument to that call, the parentheses can be omitted entirely:

run { println("...") }

— https://kotlinlang.org/docs/reference/lambdas.html#passing-a-lambda-to-the-last-parameter