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Date: Mon, 23 Feb 2009 19:27:05 +0900 (JST)
Message-Id: <20090223.192705.191392073.garrigue@math.nagoya-u.ac.jp>
To: darioteixeira@yahoo.com
Cc: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Unusual type declaration and Sexplib
From: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
In-Reply-To: <168968.6250.qm@web111509.mail.gq1.yahoo.com>
References: <168968.6250.qm@web111509.mail.gq1.yahoo.com>
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X-Spam: no; 0.00; foobar:01 sexp:01 syntax:01 sig:01 foobar:01 foo:01 val:01 foo:01 val:01 struct:01 sig:01 sexp:01 struct:01 recursively:01 caml-list:01 

From: Dario Teixeira <darioteixeira@yahoo.com>

> I'm having some trouble serialising via Sexplib a data structure defined
> recursively.  Consider module M defined below; note how type foobar_t includes
> a "with sexp" declaration, telling the Sexplib syntax extension to create
> (de)serialisers automatically.  However, type t cannot rely on that automatism,
> because type declarations with the "as" operator are not fully supported.
> Therefore, I need to create the (de)serialisers for this type manually.

You program below is exactly equivalent to the following, without as.
Or si your real code something different?

module M:
sig
        type 'a foobar_t =
                [ `Foo of int
                | `Bar of 'a list ]

        type t = private [< t foobar_t ]

        val foo: int -> t
        val bar: t list -> t
end =
struct
        type 'a foobar_t =
                [ `Foo of int
                | `Bar of 'a list ]

        type t = t foobar_t

        let foo x = `Foo x
        let bar x = `Bar x
end

Jacques Garrigue

> module M:
> sig
>         type 'a foobar_t =
>                 [ `Foo of int
>                 | `Bar of 'a list
>                 ] with sexp
> 
>         type t = private [< 'a foobar_t ] as 'a
> 
>         val foo: int -> t
>         val bar: t list -> t
> end =
> struct
>         type 'a foobar_t =
>                 [ `Foo of int
>                 | `Bar of 'a list
>                 ] with sexp
> 
>         type t = 'a foobar_t as 'a
> 
>         let foo x = `Foo x
>         let bar x = `Bar x
> end