From: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
To: Markus Mottl <markus.mottl@gmail.com>
Cc: OCaML List Mailing <caml-list@inria.fr>
Subject: Re: [Caml-list] Covariant GADTs
Date: Tue, 4 Oct 2016 19:33:59 +0900 [thread overview]
Message-ID: <427FEE0F-28E7-4A77-8ADB-8ACE5BBA35E5@math.nagoya-u.ac.jp> (raw)
In-Reply-To: <CAP_800r15rSiVP5r8R-aS5tTyza-tcPMSasXtyJue6-N5bPo4Q@mail.gmail.com>
On 2016/09/21 06:07, Markus Mottl wrote:
>
> Has the OCaml team ever considered implementing existentially
> quantified type variables for record fields? Having given it some
> superficial thought, I didn't see any obvious reason why it would be
> impossible, though it would be admittedly more difficult than the
> usual (universally quantified) polymorphic record fields.
There is no such thing for individual record fields, but note that
inline records already give you that for type variable scoping the whole
record.
type t = T : {x: 'a; f: 'a -> int} -> t
let g (T r) = r.f r.x
or for your example:
| Elt : {mutable prev : (‘el, ‘kind) t} -> (‘el, [`elt]) t
Non-quantified type variables in a GADT constructor are existential, and you can
still use explicit quantification for universals.
Jacques
next prev parent reply other threads:[~2016-10-04 10:34 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-17 17:38 Markus Mottl
2016-09-18 8:17 ` Petter A. Urkedal
2016-09-19 1:52 ` Markus Mottl
2016-09-19 8:58 ` octachron
2016-09-19 10:18 ` Mikhail Mandrykin
2016-09-19 13:37 ` Mikhail Mandrykin
2016-09-19 14:46 ` Markus Mottl
2016-09-19 14:53 ` Mikhail Mandrykin
2016-09-19 15:03 ` Markus Mottl
2016-09-20 21:07 ` Markus Mottl
2016-09-21 10:11 ` Lukasz Stafiniak
2016-09-21 10:14 ` Lukasz Stafiniak
2016-09-21 17:04 ` Markus Mottl
2016-09-21 21:40 ` Gabriel Scherer
2016-09-22 0:39 ` Markus Mottl
2016-09-24 5:09 ` Yaron Minsky
2016-10-04 10:33 ` Jacques Garrigue [this message]
2016-09-19 14:39 ` Markus Mottl
2016-09-19 10:05 ` Goswin von Brederlow
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