can someone explain or point documentation what is the reasoning behind that using return in list.ma...

# getting-started

[Jukka Siivonen]

can someone explain or point documentation what is the reasoning behind that using return in list.map { return xxx } is not actually return of value of the lambda function? and what is the use case where this return behavior would be useful?

[edwardwongtl]

You mean the return in map actually returns to a outer scope?

[Andreas Sinz]

https://kotlinlang.org/docs/reference/inline-functions.html#non-local-returns

[Jukka Siivonen]

Yes, "non-local returns" it is

[elizarov]

The reasoning is in consistency. In Kotlin, return is consistent in that it returns from the enclosing fun by default. From lambdas you don’t usually return — you program them (usually) in functional style where their value is the last expression.

[Jukka Siivonen]

I made a silly bug because I tried to write

list.map { it -> 
    return if (condition) {
        Foo()
    } else Bar()
}

[Jukka Siivonen]

which of course did not work, so I quickly changed it to

[Jukka Siivonen]

list.map { it ->
    if (condition) { 
        Foo()
    } 
    Bar()
}

[Jukka Siivonen]

which I then found out should be

list.map { it ->
    if (condition) {
        Foo()
    } else {
        Bar()   
    }
}

[elizarov]

It makes sense to add some kind of inspection that would recognize mistake of the first type. It should be easy to detect.

[Jukka Siivonen]

Agreed