From: Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>
To: datta@math.berkeley.edu
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] lablgtk polymorphic variants question
Date: Mon, 19 Mar 2001 19:27:36 +0900 [thread overview]
Message-ID: <20010319192736S.garrigue@kurims.kyoto-u.ac.jp> (raw)
In-Reply-To: <20010318221350.A20863@blue1.berkeley.edu>
From: Ruchira Datta <datta@math.berkeley.edu>
> I tried to compile lablgtkmathview but ran into an error. I would guess
> that it probably compiled under OCaml 3.00 but doesn't for me since I have
> 3.01. I have lablgtk 1.2.0. (Everything is from Sven Luther's Debian
> packages, except lablgtkmathview and mlminidom which don't seem to be
> packaged yet.) The error:
[...]
> The declaration of MathView.get_frame is on lines 85-86 of gtkMathView.ml,
> in module MathView:
>
> external get_frame : [>`math_view] obj -> [`frame] obj =
> "ml_gtk_math_view_get_frame"
This is wrong. This should be:
external get_frame : [>`math_view] obj -> Gtk.frame obj =
"ml_gtk_math_view_get_frame"
> The declaration of Gtk.frame is on line 95 of gtk.ml:
>
> type frame = [`widget|`container|`bin|`frame]
>
> I guess I don't fully understand polymorphic variants. It would have seemed
> to me that if (new GBin.frame) expects an argument of type Gtk.frame, then
> something of type [ 'frame] should satisfy it. Why should it be necessary
> that all four variants [`widget|`container|`bin|`frame] be able to occur?
> I thought that the inferred type of a function would always allow less
> variants in its argument.
LablGTK uses an encoding of widget types, in variant types, were
variant types are used as capacities. This can seem a bit unusual, but
you can see it in the fact the Gtk.obj abstract type is contravariant.
Jacques Garrigue
-------------------
To unsubscribe, mail caml-list-request@inria.fr. Archives: http://caml.inria.fr
next prev parent reply other threads:[~2001-03-19 10:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-03-19 6:13 Ruchira Datta
2001-03-19 9:43 ` Sven LUTHER
2001-03-19 13:58 ` Stefano Zacchiroli
2001-03-19 10:27 ` Jacques Garrigue [this message]
2001-03-19 17:33 Ruchira Datta
2001-03-20 5:23 Ruchira Datta
2001-03-20 14:03 ` Jacques Garrigue
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=20010319192736S.garrigue@kurims.kyoto-u.ac.jp \
--to=garrigue@kurims.kyoto-u.ac.jp \
--cc=caml-list@inria.fr \
--cc=datta@math.berkeley.edu \
/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).