MutableListExt.kt

typealias IteratorProducer<T> = (index: Int) -> T

fun <T> MutableList<T>.addAll(count: Int, producer: IteratorProducer<T>) = addAll(collection(count, producer))

fun <T> iterable(count: Int, producer: IteratorProducer<T>) = object : Iterable<T> {
    override fun iterator(): Iterator<T> = iterator(count, producer)
}

fun <T> sequence(count: Int, producer: IteratorProducer<T>) = object : Sequence<T> {
    override fun iterator(): Iterator<T> = iterator(count, producer)
}

fun <T> iterator(count: Int, producer: IteratorProducer<T>) = object : Iterator<T> {

    private var next = 0

    override fun hasNext(): Boolean = next < count

    override fun next(): T = when {
        hasNext() -> producer(next++)
        else -> throw IndexOutOfBoundsException("next index: $next, count: $count")
    }
}

fun <T> collection(count: Int, producer: IteratorProducer<T>) = object : Collection<T> {

    override val size: Int = count

    override fun isEmpty(): Boolean = count == 0

    override fun iterator(): Iterator<T> = iterator(count, producer)

    override fun containsAll(elements: Collection<T>): Boolean = false

    override fun contains(element: T): Boolean = false
}