inline fun <T, R> MongoIterable<T>.foldIndexed(initial: R, crossinline operation: (index: Int, acc: R, T) -> R): R (source)
Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element with its index in the original collection.
operation - function that takes the index of an element, current accumulator value
and the element itself, and calculates the next accumulator value.