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References: <1342371289.7422.YahooMailNeo@web111511.mail.gq1.yahoo.com> <Prayer.1.3.5.1207152055260.20778@hermes-2.csi.cam.ac.uk>
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Date: Mon, 16 Jul 2012 07:45:29 -0700 (PDT)
From: Dario Teixeira <darioteixeira@yahoo.com>
Reply-To: Dario Teixeira <darioteixeira@yahoo.com>
To: "caml-list@inria.fr" <caml-list@inria.fr>
In-Reply-To: <Prayer.1.3.5.1207152055260.20778@hermes-2.csi.cam.ac.uk>
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Subject: Re: [Caml-list] GADTs and parsers

Hi,

> What about something like (not really tested):

>=20
> type _ guard_t =3D=A0 =A0 | Nonlinked: [> `Nonlink ] guard_t
> =A0  | Either: [> `Nonlink | `Link ] guard_t
>=20
> let inlineseq_from_astseq seq =3D
> let rec process : type a. a guard_t -> ast_t -> a inline_t =3D=A0 fun gua=
rd=20
> ast ->=A0  match (guard, ast) with
> =A0 | (Nonlinked, Ast_Text txt)=A0  -> Text txt
> =A0 | (Either, Ast_Text txt)=A0 =A0 =A0 -> Text txt
> =A0 | (x, Ast_Bold xs)=A0 =A0 =A0 =A0 =A0 =A0 -> Bold (List.map (process =
x) xs)
> =A0 | (Either, Ast_Link lnk)=A0 =A0 =A0 -> Link lnk
> =A0 | (Either, Ast_Mref (lnk, xs))=A0 =A0 =A0 =A0  -> Mref (lnk, List.map=
 (process=20
> Nonlinked) xs)=A0  | _=A0  -> assert false
> in List.map (process Either) seq

I see what you mean -- using an auxiliary GADT basically.
Nice technique to keep in mind -- thanks!

Cheers,
Dario