you mean by using a `(T) -> (R?)` and then `map...

# getting-started

[Ran Magen]

you mean by using a (T) -> (R?) and then mapNotNull? That'd work (assuming T : Any) but it would create an intermediate list, which ideally I'd like to avoid.

[Evan R.]

If you’re worried about intermediate lists, you may want to try .asSequence(). Then you can just do:

val sampleList = listOf(1, 2, 3)
val filterMappedList = sampleList.asSequence().filter { it > 1 }.map { it * 2 }.toList()

[arekolek]

you mean by using a (T) -> (R?) and then mapNotNull?

No, I think Karel meant:

inline fun <T, R : Any> List<T>.collect(
        predicate: (T) -> Boolean,
        transform: (T) -> R
): List<R> {
    return mapNotNull {
        if (predicate(it)) {
            transform(it)
        } else {
            null
        }
    }
}

[karelpeeters]

Yes @arekolek, that's what I meant, thanks! I usually do something like that but in-place of course.