From: art yerkes <ayerkes@speakeasy.net>
To: caml-list@inria.fr
Subject: Re: [Caml-list] Subclasses and pattern matching
Date: Fri, 19 Sep 2003 10:58:52 -0500 [thread overview]
Message-ID: <20030919105852.24b1ea03.ayerkes@speakeasy.net> (raw)
In-Reply-To: <20030919152252.GA30989@henchmonkey.org>
On Fri, 19 Sep 2003 11:22:52 -0400
katre <katre@henchmonkey.org> wrote:
> Richard Jones wrote:
> >
> > Possibly I'm being dumb here, but wouldn't it be better to use
> > a union type, eg:
> >
> > type num = Int of int | Float of float
> >
>
> Yes, except for two facts:
>
> a) Each different type has different data available (some are ints, some
> strings, some more complex)
> b) Each different type has a lot of data. I don't really want to
> specify a 10-member tuple for each constructor :)
> c) Where the data is used, I want to match two or three different types,
> and then call a default method with anything left over. With a union, I
> have to deal with every possible type, or do nothing with the data.
>
> To clarify, using your type above, I can't do
>
> match n with
> Int(i) -> print_int i
> | _ -> print_int some_data_from_n
>
> Remember, all of my structures have many more than 1 piece of data. A
> class inheritance really is the best way to model the data structure, I
> just want to be able to pattern match on it.
>
> katre
>
You could wrap your items in a union:
exception NoExternalRepForBase
type 'a base_extern_t =
Derived1 of 'a | Derived2 of 'a
class virtual base =
object
method virtual as_external : unit -> base base_extern_t
end
class derived1 =
object(self)
inherit base
method as_external () = Derived1 (self :> base)
end
class derived2 =
object(self)
inherit base
method as_external () = Derived2 (self :> base)
end
let l = [ (new derived2 # as_external()) ; (new derived1 # as_external()) ]
--
"Should array indices start at 0 or 1? My compromise of 0.5 was rejected
without, I thought, proper consideration."
- S. Kelly-Bootle
-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
next prev parent reply other threads:[~2003-09-19 15:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-19 14:21 katre
2003-09-19 14:52 ` Richard Jones
2003-09-19 15:22 ` katre
2003-09-19 15:58 ` art yerkes [this message]
[not found] ` <20030919155431.GA31387@henchmonkey.org>
2003-09-19 16:32 ` art yerkes
2003-09-19 16:40 ` Claude Marche
2003-09-20 15:00 ` Michal Moskal
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20030919105852.24b1ea03.ayerkes@speakeasy.net \
--to=ayerkes@speakeasy.net \
--cc=caml-list@inria.fr \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).