OCaml missing standard library functions

Question

I noticed that some standard library functions are missing in my installation of OCaml (I followed the instructions for Ubuntu here). For example, if I type

#show Hashtbl;;

in the utop toplevel, I get the following signature

module Hashtbl: sig
  type ('a, 'b) t
  val create : ?random:bool -> int -> ('a, 'b) t
  val clear : ('a, 'b) t -> unit
  val reset : ('a, 'b) t -> unit
  val copy : ('a, 'b) t -> ('a, 'b) t
  val add : ('a, 'b) t -> 'a -> 'b -> unit
  val find : ('a, 'b) t -> 'a -> 'b
  val find_all : ('a, 'b) t -> 'a -> 'b list
  val mem : ('a, 'b) t -> 'a -> bool
  val remove : ('a, 'b) t -> 'a -> unit
  val replace : ('a, 'b) t -> 'a -> 'b -> unit
  val iter : ('a -> 'b -> unit) -> ('a, 'b) t -> unit
  val fold : ('a -> 'b -> 'c -> 'c) -> ('a, 'b) t -> 'c -> 'c
  val length : ('a, 'b) t -> int
  val randomize : unit -> unit
  type statistics = {
    num_bindings : int;
    num_buckets : int;
    max_bucket_length : int;
    bucket_histogram : int array;
  }
  val stats : ('a, 'b) t -> statistics
  module type HashedType =
    sig type t val equal : t -> t -> bool val hash : t -> int end
  module type S =
    sig
      type key
      type 'a t
      val create : int -> 'a t
      val clear : 'a t -> unit
      val reset : 'a t -> unit
      val copy : 'a t -> 'a t
      val add : 'a t -> key -> 'a -> unit
      val remove : 'a t -> key -> unit
      val find : 'a t -> key -> 'a
      val find_all : 'a t -> key -> 'a list
      val replace : 'a t -> key -> 'a -> unit
      val mem : 'a t -> key -> bool
      val iter : (key -> 'a -> unit) -> 'a t -> unit
      val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
      val length : 'a t -> int
      val stats : 'a t -> statistics
    end
  module Make : functor (H : HashedType) -> sig  end
  module type SeededHashedType =
    sig type t val equal : t -> t -> bool val hash : int -> t -> int end
  module type SeededS =
    sig
      type key
      type 'a t
      val create : ?random:bool -> int -> 'a t
      val clear : 'a t -> unit
      val reset : 'a t -> unit
      val copy : 'a t -> 'a t
      val add : 'a t -> key -> 'a -> unit
      val remove : 'a t -> key -> unit
      val find : 'a t -> key -> 'a
      val find_all : 'a t -> key -> 'a list
      val replace : 'a t -> key -> 'a -> unit
      val mem : 'a t -> key -> bool
      val iter : (key -> 'a -> unit) -> 'a t -> unit
      val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
      val length : 'a t -> int
      val stats : 'a t -> statistics
    end
  module MakeSeeded : functor (H : SeededHashedType) -> sig  end
  val hash : 'a -> int
  val seeded_hash : int -> 'a -> int
  val hash_param : int -> int -> 'a -> int
  val seeded_hash_param : int -> int -> int -> 'a -> int
end

Notice the absence of Hashtbl.filter_map_inplace and Hashtbl.is_randomized, which are listed in the online documentation.

1. Why are the signatures different?
2. Where do I get the right library (or the right documentation)?

Answer 1

It's a version issue. filter_map_inplace appears to have been released in 4.03, is_randomized in 4.02. Ubuntu's OCaml package uses version 4.01.

You can find newer versions by using Anil Madhavapeddy's PPAs

add-apt-repository ppa:avsm/ppa
apt-get update
apt-get install ocaml ocaml-native-compilers camlp4-extra opam

(sourced from https://opam.ocaml.org/doc/Install.html)

Or once you have OPAM you can use it to install a newer version.

opam switch 4.02.1
eval `opam config env`