kotlin lambda expressions as optional parameter

Question

How can I pass lambda expression as optional parameter in Kotlin language

val max = { a: Int, b: Int ->
  if (a > b)
      a
  else
      b
}

I have to pass above thing is like optional parameter

Answer 1

The following defines a function that accepts a function, and specifies a default value for the passed function if none is supplied.

fun foobar(fn: (a: Int, b: Int) -> Int = { a: Int, b: Int -> if (a > b) a else b }) {
  println(fn(42, 99))
}

You can pass your own functions:

val min = { a: Int, b: Int -> if (a <= b) a else b }
foobar(min)

val max = { a: Int, b: Int -> if (a > b) a else b }
foobar(max)

You can omit the function and use the default:

foobar()

Alternatively you could refer to the standard library maxOf function as the default, rather than write your own:

fun foobar(fn: (a: Int, b: Int) -> Int = ::maxOf) {
  println(fn(42, 99))
}