From: skaller <skaller@ozemail.com.au>
To: Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>
Cc: BeckW@t-systems.com, caml-list@inria.fr
Subject: RE: [Caml-list] strange behaviour with variants and "cannot be g eneralized"
Date: 10 Sep 2003 20:39:28 +1000 [thread overview]
Message-ID: <1063190367.2119.149.camel@localhost.localdomain> (raw)
In-Reply-To: <20030910171830O.garrigue@kurims.kyoto-u.ac.jp>
On Wed, 2003-09-10 at 18:18, Jacques Garrigue wrote:
> From: "Beck01, Wolfgang" <BeckW@t-systems.com>
> In that case we have now polymorphic fields.
> type mix = {data: 'a. 'a -> 'a ; mutable count: int}
> let r = {data = (fun x -> x); count = 0}
>
> So, I think this is a good idea in itself, but before I try again
> introducing this improvement, I need a few compelling examples to
> justify the effort.
Curious: this isn't yet dual to the variants: the field values
are polymorphic, by the record itself is not. Wouldn't one like
to have a record of a set of tags where the typing is like:
match { `A 1; `B 2 } with
| { `A x } -> ...
that is, allow subtyping based on tag sets?
[Hmm .. what is the variance of the field values ?]
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next prev parent reply other threads:[~2003-09-10 10:40 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-10 7:10 Beck01, Wolfgang
2003-09-10 8:12 ` Fernando Alegre
2003-09-10 8:18 ` Jacques Garrigue
2003-09-10 10:39 ` skaller [this message]
2003-09-10 9:48 ` skaller
2003-09-10 11:34 ` Frederic De Jaeger
-- strict thread matches above, loose matches on Subject: below --
2003-09-09 14:13 Beck01, Wolfgang
2003-09-09 19:17 ` Didier Remy
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