foldRightIndexed

inline fun <R> CharSequence.foldRightIndexed(
    initial: R, 
    operation: (index: Int, Char, acc: R) -> R
): R

Accumulates value starting with initial value and applying operation from right to left to each character with its index in the original char sequence and current accumulator value.

Parameters

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