Re: [Caml-list] open extensible types representation

[Leo White <lpw25@cam.ac.uk>]

> The rebinding of constructors is interesting. What are uses case apart
> from reducing verbosity in some cases?

Naming a constructor created by a functor.

For example, the following excerpts from my own toy example
(testsuite/tests/typing-extensions/msg.ml in the ocaml sources):

    module Msg : sig

      type 'a tag

      (* ... *)

      module Define (D : Desc) : sig
        type 'a tag += C : D.t tag
      end

    end = struct

      type 'a tag = ..

      (* ... *)

    end

    (* ... *)

    module StrM = Msg.Define(struct
      type t = string
      (* ... *)
    end);;

    type 'a Msg.tag += String = StrM.C;;

Note that the `Msg.tag` type has been made abstract, so the `Define`
functor is the only method of creating new constructors.

The rebinding gives the `String` constructor a meaningful name, and
allows you to expose it in your interface rather than expose all of
`StrM`.

Regards,

Leo