Kotlin - lambda argument outside parenthesis-CodePudding

having following function

fun functionOne(element: Int, func1: (index: Int) -> Unit) {
    println("element=$element")
    func1(element)
}

I can call it that way:

functionOne(element = 123, func1 = {index -> println("index: $index")})

no compilator complains

functionOne(123,  {index -> println("index: $index")})

now compilator suggests Lambda argument should be moved out of parentheses

functionOne(123) { index -> println("index: $index") }

no complains

however, unless I don't get it right, this begavior is limited to exactly one lambda argument, that is having

fun functionTwo(element: Int, func1: (index: Int) -> Unit, func2: (index: Int) -> Unit) {
    println("element=$element")
    func1(element)
    func2(element)
}

I can make a call like this

functionTwo(123, { index -> println("index: $index")},  { index -> println("index2: $index")})

but this one does not compile

functionTwo(456) {index -> println("index: $index"} { index -> println("index2: $index")})

can you please confirm that or let me know to move lambda arguments out of parentheses

thanks!

CodePudding user response：

According to the documentation, only trailing lambdas can be placed outside the parenthesis:

Passing trailing lambdas

According to Kotlin 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 in that call, the parentheses can be omitted entirely:
run { println("...") }

This implies that you can not move the second-to-last lambda expression outside of the parenthesis, and thus that you cannot move multiple lambda expressions out of the parenthesis.