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From: Leo White <lpw25@cam.ac.uk>
To: Milan =?utf-8?Q?Stanojevi=C4=87?= <milanst@gmail.com>
Cc: Alain Frisch <alain.frisch@lexifi.com>,  Jeremie Dimino <jdimino@janestreet.com>,  Caml List <caml-list@inria.fr>
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	("Milan \=\?utf-8\?Q\?Stanojevi\=C4\=87\=22's\?\= message of "Wed, 14 May 2014
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Subject: Re: [Caml-list] open extensible types representation

> 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