Evaluate code block in Kotlin (to hide variables inside scope)

Question

In Scala, you can write

val x = {
  ... do some complex computations ..
  42
}

to hide stuff inside of the code block.

The closest I came in Kotlin is:

val x = {
  ... do some complex computations ..
  42
}()

Is there a better way?

EDIT:

• isn’t run {} in the above example essentially the same
• is calling run costly?

ANSWER:

• using run {} inlines, whereas {}() does NOT (see my own answer below)

Answer 1

Use the run function. It takes a function as a parameter, runs it and returns the result.

val x = run {
  ... do some complex computations ..
  42
}

The run function is inlined, so it will have no performance overhead.