In F# programs I prefer to use

[<RequireQualifiedAccess>]

type MyType =

    | FirstOption of string

    | SecondOption of int

so that in code that uses MyType I am forced to write MyType.FirstOption instead of just FirstOption. Is there any way to force this in OCaml?

You can get a similar effect by defining the type in a module.

$ ocaml

        OCaml version 4.02.1



# module MyType = struct

    type t = FirstOption of string | SecondOption of int

    end    ;;

module MyType : sig type t = FirstOption of string | SecondOption of int end

# MyType.FirstOption "abc";;

- : MyType.t = MyType.FirstOption "abc"

# FirstOption "abc";;

Error: Unbound constructor FirstOption

#

If you do it this way, the name of the type (as you can see) is MyType.t.