val foldi_left: (int -> 'a -> 'b -> 'a) -> int -> 'a -> 'b list -> 'a
+val rev_mapi: (int -> 'b -> 'a) -> int -> 'b list -> 'a list
+
val rev_map_append: ('a -> 'b) -> 'a list -> 'b list -> 'b list
+
+val split_at: int -> 'a list -> 'a list * 'a list