From: Remi VANICAT <vanicat@labri.u-bordeaux.fr>
To: caml-list@inria.fr
Subject: Re: [Caml-list] Allowing many types
Date: 08 Feb 2002 17:53:41 +0100 [thread overview]
Message-ID: <87vgd7oqy2.dlv@wanadoo.fr> (raw)
In-Reply-To: <20020208163700.GA1452@mandelbrot.house>
Ceri Storey <cez@pkl.net> writes:
> I've been trying to do something similar with something i'm writing, and
> the only thing i could come up with is to store data in an object, and
> then subclass it. The problem here is that once the object has been
> coerced to the general type, it cannot be coerced back again. ie: if you
> subclass the object to say, impliment integers, then it's not possible
> for it to be coerced back to the integer type so you can retreive / act
> on the value. (withoug using Obj.magic, that is)
>
> If anyone has any good ideas, I'd be happy to hear about them too.
polymorphic variant me be the answer, because you can get back the
type :
let fn1 (`Int x) = float_of_int x
let fn2 (`Float x) = x
let fn x =
match x with
| `Int _ as i -> fn1 i
| `Float _ as f -> fn2 f
| _ -> raise (Invalid_argument "fn")
(be aware that
let fn x =
match x with
| `Int _ as i -> fn1 x
| `Float _ as f -> fn2 x
| _ -> raise (Invalid_argument "fn")
doesn't work)
extensible function from camlp4 library may be also useful, but
I've not try it yet.
--
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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next prev parent reply other threads:[~2002-02-08 16:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-08 2:29 Ryan Tarpine
2002-02-08 16:37 ` Ceri Storey
2002-02-08 16:53 ` Remi VANICAT [this message]
2002-02-10 17:42 ` Ceri Storey
2002-02-11 1:43 Ryan Tarpine
2002-02-11 10:53 ` Ceri Storey
2002-02-11 11:48 ` Remi VANICAT
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