From: Richard Jones <rich@annexia.org>
To: Christophe TROESTLER <Christophe.Troestler+ocaml@umh.ac.be>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] What does underscore mean in this type expression?
Date: Sat, 30 Aug 2008 20:29:36 +0100 [thread overview]
Message-ID: <20080830192936.GB7078@annexia.org> (raw)
In-Reply-To: <20080830.155754.457039520284782231.Christophe.Troestler+ocaml@umh.ac.be>
On Sat, Aug 30, 2008 at 03:57:54PM +0200, Christophe TROESTLER wrote:
> On Sat, 30 Aug 2008 14:03:10 +0100, Richard Jones wrote:
> >
> > > # let x = ref `X;;
> > > val x : _[> `X ] ref = {contents = `X}
> >
> > OK ... so how to get rid of the error? Even supplying a full type for
> > get_domains in the implementation doesn't get rid of it.
> >
> > Here's the code if anyone wishes to try:
> >
> > http://www.annexia.org/tmp/libvirt.mli
> > http://www.annexia.org/tmp/libvirt.ml
> >
> > $ ocamlc -c libvirt.mli
> > $ ocamlc -c libvirt.ml
>
> Here is the crux of your problem
>
> let f = let a = ref 0 in fun (x : [> `R ]) -> x;;
>
> If you hoist [let have_list_all_domains = ref None] outside [let
> get_domains], then it works fine. The type checker could certainly be
> slightly improved [1] there but I do not know how difficult it is.
Yes, that fixed it, thanks.
> [1] And maybe also the compiler: a rough check seem to indicate that
> hiding the variable in the definition of f is slightly slower.
It use this idiom quite a lot to emulate private (static) variables.
Rich.
--
Richard Jones
Red Hat
prev parent reply other threads:[~2008-08-30 19:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-30 11:27 Richard Jones
2008-08-30 11:38 ` [Caml-list] " Christophe TROESTLER
2008-08-30 13:03 ` Richard Jones
2008-08-30 13:57 ` Christophe TROESTLER
2008-08-30 19:29 ` Richard Jones [this message]
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