type ('elements, 'element) t
val first_element : (('head, _) cons, 'head) t
val of_tail : ('tail, 'element) t ‑> ((_, 'tail) cons, 'element) t
val within : ('inner, 'element) t ‑> suffix:('outer, 'inner) Suffix_index.t ‑> ('outer, 'element) t
Transform an index to find an element within a suffix of the list.
/O(n)/ allocation and work.