just drawing a blank here: is the not a shortcut for

if (predicate(x)) f(x) else null

?

you could

x.takeIf(::predicate)?.let(::f)

if

x

is not null, but the way you wrote it with

if

is clearer

yeah, I had this and it's not nicer, so reverted. But then I thought I missed something like a

Any?.runIf

. Seems I was mistaken

We are considering adding

runIf

function to stdlib

fun <T> runIf(cond: Boolean, block: () -> T): T? = if (cond) block() else null

But this function requires new kind of contracts which allows to propagate smartcast info from condition to lambda body

fun test(x: String?) {
    val y = runIf(x != null) {
        x.length // should be smartcast to String
    }
}

And those new contracts will be possible to implement only in K2 compiler

nice. I have written and used an

.applyIf()

extension in several projects (even without smartcasting); I think I would get more use out of that than

runIf()

but it's almost equivalent

wouldn't it conform more to the naming convention in Kotlin, if the function was called

runIfOrNull

!?

There is no final decision yet about this function