[Caml-list] Converting "fun ... (type t) ..." into a caml < 3.12 code

[Julien Signoles <julien.signoles@gmail.com>]

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Sorry, forgot the list...

---------- Forwarded message ----------
From: Julien Signoles <julien.signoles@gmail.com>
Date: 2011/1/26
Subject: Re: [Caml-list] Converting "fun ... (type t) ..." into a caml <
3.12 code
To: Stefan Holdermans <stefan@vectorfabrics.com>




2011/1/26 Stefan Holdermans <stefan@vectorfabrics.com>

 > How to convert the following ocaml 3.12 code into a typable ocaml < 3.12
> code?
>
> Coincidentally, earlier today, I ran into a situation not that different
> from the one you describe. I haven't come up with a satisfying solution yet.
>
> > I have a solution using Obj. Is it possible without Obj?
>
> Are you willing to share this solution?
>

====
let g (x:'a) =

  let module S =
    Set.Make(struct
      type t = Obj.t

      let compare = Pervasives.compare
      let equal = ( = )
    end)
  in
  (Obj.magic (S.elements (S.singleton (Obj.repr x))) : 'a list)
(* less efficient but using Obj.obj instead of Obj.magic: *)
(*  List.rev (S.fold (fun o acc -> (Obj.obj o:'a) :: acc) (S.singleton
(Obj.repr x)) []) *)
====

Note that:
1) I'm pretty sure someone who initials are XL will be unhappy with such a
solution
2) For a real-world application [*], I prefer to leave a known bug instead
of fixing it using such a solution... And either waiting for a solution
without Obj or waiting for a future day where our software will require
ocaml 3.12

--
Julien

[*] Frama-C (http://frama-c.com)

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