val group_by : ?cmp:('a -> 'a -> int) -> ('a * 'b) list -> ('a * 'b list) list
(** Group a sorted list of pairs by the first element of the pair. *)
+
+val range : int -> int -> int list
+(** [range a b] returns the list of integers [a <= i < b].
+ If [a >= b] then the empty list is returned.
+*)