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.

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()

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
        }
    }
}

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