From: Taylan Kammer <taylan.kammer@gmail.com>
To: Damien Mattei <damien.mattei@gmail.com>, guile-devel@gnu.org
Subject: Re: new function
Date: Sun, 19 Sep 2021 23:38:59 +0200 [thread overview]
Message-ID: <147c2fb4-75d6-7cf6-4f4a-4edd996b0a4a@gmail.com> (raw)
In-Reply-To: <CADEOadfF+rR=fW0fS-PkQkDN8EHFB1sJnkeePMJyc23m9shLgA@mail.gmail.com>
On 19.09.2021 09:54, Damien Mattei wrote:
> hello,
> i'm developing an extension to Scheme
> and i need a procedure or macro that define a variable only if it is not bind and if it is just set! it.
>
> I can not do it in Guile or any Scheme,and i'm desperately searching a way to do that. I finally conclude that it can be done only by adding it in the language.
>
> Can someone include a such function in Guile next release?
> i know guile have a predicate defined? to test binfing of a vairable but writing a macro with it is not possible because define can be used in an expression context.
>
> Thank in advance for any help
> Damien
What is the utility of such a function? Since Scheme is lexically scoped,
it's generally obvious whether a variable has already been defined or not,
rendering such an operation useless.
If you're constructing code from outside input so that you don't know
whether a provided variable name represents a variable that's already been
defined or not, then you could use the module reflection API:
https://www.gnu.org/software/guile/manual/html_node/Module-System-Reflection.html
Sounds like 'module-define!' does exactly what you ask for. I wonder what
exactly your use-case is though. Chances are that your use-case is best
served with a simple data structure like a hash table...
--
Taylan
next prev parent reply other threads:[~2021-09-19 21:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-19 7:54 new function Damien Mattei
2021-09-19 14:41 ` Matt Wette
2021-09-19 14:43 ` Matt Wette
2021-09-19 21:38 ` Taylan Kammer [this message]
2021-09-21 12:26 ` Damien Mattei
2021-09-22 8:44 ` Damien Mattei
2021-09-22 9:06 ` William ML Leslie
2021-09-22 9:53 ` Damien Mattei
2021-09-22 18:51 ` Taylan Kammer
2021-09-22 21:52 ` William ML Leslie
2021-09-23 8:40 ` Damien Mattei
2021-09-23 19:03 ` Taylan Kammer
2021-09-23 17:27 ` Damien Mattei
2021-09-23 18:00 ` Maxime Devos
2021-09-23 20:27 ` Taylan Kammer
2021-09-23 20:42 ` Damien Mattei
2021-09-23 20:48 ` Taylan Kammer
2021-09-23 21:53 ` Damien Mattei
2021-09-24 4:41 ` Damien Mattei
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=147c2fb4-75d6-7cf6-4f4a-4edd996b0a4a@gmail.com \
--to=taylan.kammer@gmail.com \
--cc=damien.mattei@gmail.com \
--cc=guile-devel@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).