(last-index-of s value) (last-index-of s value from-index)
Return last index of value (string or char) in s, optionally searching backward from from-index or nil if not found.
;; 1. Just find index of char
user=> (last-index-of "aaaaaa" "a")
5
user=> (last-index-of "abcde" "c")
2
;; 2. Optionally searching example
user=> (last-index-of "abcde" "e" 0)
;;=> nil
user=> (last-index-of "abcde" "e" 1)
;;=> nil
user=> (last-index-of "abcde" "e" 2)
;;=> nil
user=> (last-index-of "abcde" "e" 3)
;;=> nil
user=> (last-index-of "abcde" "e" 4)
;;=> 4
user=> (last-index-of "abcde" "e" 5)
;;=> 4