foldIndexed

inline fun <T, R> Sequence<T>.foldIndexed(
    initial: R, 
    operation: (index: Int, acc: R, T) -> R
): R

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 sequence.

Parameters

operation - function that takes the index of an element, current accumulator value and the element itself, and calculates the next accumulator value.