From: ludo@gnu.org (Ludovic Courtès)
To: guile-user@gnu.org
Subject: Re: Accessing multiple values from C
Date: Tue, 01 Nov 2011 23:57:25 +0100 [thread overview]
Message-ID: <87fwi7cuy2.fsf@gnu.org> (raw)
In-Reply-To: CANdC_RDgPAB_=Cq88-ecGJz4W-YJTUUJFhpXJ6Zs7p2nQzrcYQ@mail.gmail.com
Hi,
Julian Graham <joolean@gmail.com> skribis:
> I was playing around with some C code that uses the new R6RS
> bytevector ports, and I noticed that there doesn't seem to be an easy
> way (a la `let-values' or `receive') to access multiple return values
> from C. I've resorted to doing:
>
> scm_struct_ref (foo, SCM_INUM0);
>
> ...which is almost certainly not future-proof. All I want to do is
> access these values as a pair or list.
Values were already structs in 1.8, so that’s OK.
Perhaps this should be documented though, and C accessors could be
provided.
> Is there a Right Way to do that?
Yes: write Scheme code! :-)
In 1.8 multiple-values were always a struct, which had to be allocated
each time multiple values were returned. In 2.0 it’s a struct only if
it has to cross the Scheme/C boundary–otherwise the values are stored on
the VM stack.
Thanks,
Ludo’.
next prev parent reply other threads:[~2011-11-01 22:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-01 15:34 Accessing multiple values from C Julian Graham
2011-11-01 22:57 ` Ludovic Courtès [this message]
2012-01-09 18:54 ` Andy Wingo
2012-01-09 19:00 ` Julian Graham
2012-01-12 4:50 ` Julian Graham
2012-01-15 21:47 ` Ludovic Courtès
2012-01-16 9:05 ` Andy Wingo
2012-01-18 3:15 ` Mark H Weaver
2012-01-18 16:20 ` Andy Wingo
2012-01-18 20:19 ` Ludovic Courtès
2012-01-18 21:01 ` Mark H Weaver
2012-01-18 21:44 ` Ludovic Courtès
2012-01-18 21:47 ` Mark H Weaver
2012-01-18 23:06 ` Mark H Weaver
2012-01-18 21:01 ` Julian Graham
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
List information: https://www.gnu.org/software/guile/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87fwi7cuy2.fsf@gnu.org \
--to=ludo@gnu.org \
--cc=guile-user@gnu.org \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).