Platform and version requirements: JVM (1.4), JS (1.4), Native (1.4)

@JvmName("flatMapIndexedIterableTo") inline fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapIndexedTo(
    destination: C, 
    transform: (index: Int, T) -> Iterable<R>
): C

@JvmName("flatMapIndexedSequenceTo") inline fun <T, R, C : MutableCollection<in R>> Sequence<T>.flatMapIndexedTo(
    destination: C, 
    transform: (index: Int, T) -> Sequence<R>
): C

Appends all elements yielded from results of transform function being invoked on each element and its index in the original sequence, to the given destination.

The operation is terminal.