Below is the API for the OCaml standard library. It's directly copied over from the OCaml Manual, formatted to the Reason syntax and styled accordingly. The API docs are work-in-progress; we'll be polishing these gradually!
If you're targeting JavaScript, the API docs for BuckleScript includes all of below, plus JS-specific APIs.
module type S = sig .. end
type elt
type t
val empty : t
val is_empty : t -> bool
val mem : elt -> t -> bool
val add : elt -> t -> t
val singleton : elt -> t
val remove : elt -> t -> t
val union : t -> t -> t
val inter : t -> t -> t
val diff : t -> t -> t
val compare : t -> t -> int
val equal : t -> t -> bool
val subset : t -> t -> bool
val iter : f:(elt -> unit) -> t -> unit
val fold : f:(elt -> 'a -> 'a) -> t -> init:'a -> 'a
val for_all : f:(elt -> bool) -> t -> bool
val exists : f:(elt -> bool) -> t -> bool
val filter : f:(elt -> bool) -> t -> t
val partition : f:(elt -> bool) -> t -> t * t
val cardinal : t -> int
val elements : t -> elt list
val min_elt : t -> elt
val max_elt : t -> elt
val choose : t -> elt
val split : elt -> t -> t * bool * t
val find : elt -> t -> elt
val of_list : elt list -> t