From: Marcin Borkowski <mbork@mbork.pl>
To: help-gnu-emacs@gnu.org
Subject: Re: How the backquote and the comma really work?
Date: Thu, 25 Jun 2015 20:06:46 +0200 [thread overview]
Message-ID: <87si9ffys0.fsf@mbork.pl> (raw)
In-Reply-To: <87r3ozy9pf.fsf@web.de>
On 2015-06-25, at 19:33, Michael Heerdegen <michael_heerdegen@web.de> wrote:
> Marcin Borkowski <mbork@mbork.pl> writes:
>
>> So, I assume that when Emacs Lisp interpreter encounters a backquote
>
> It's even less mystical: backquote is just a normal macro:
>
> C-h f ` RET
Thanks. OTOH, backquote.el has more than 200 lines of code, and it is
a bit complicated (I would guess that it might contain some
optimizations/error checking/whatever). Seeing a simplistic (though
working in typical/correct cases) version might be rather illuminating,
no?
> It's also a reader macro so that you can write
>
> `thing
>
> as an abbreviation of of
>
> (` thing)
>
> but that's just a detail.
Interesting. Where is that defined?
>> If it is a list, its element are read and scanned. If any part of the
>> list (probably a nested one) begins with a comma, the whole thing after
>> the comma (be it a symbol, a list or whatever) is evaluated as usual,
>> and the result is put into the resulting list.
>>
>> Whew. Is that (more or less) right?
>
> Seems to be a reasonable mental model. Of course, the elements have
> already been read by the reader. Whether these are evaluated or not
> depends on whether the macro finds the `backquote-unquote-symbol' in
> front of them, so to say.
>
>> so a bonus question is: can I find an Emacs Lisp metacircular
>> evaluator (taking into account the quoting mechanisms) anywhere?
>
> You don't need a meta thing, since backquote is completely implemented
> in Elisp, just read the source code ;-)
See above: it is pretty much complicated compared to entry-level stuff
in SICP. (Though I guess that I will just put my shoulder to the wheel
and study the code. That might lead to more questions;-).)
> Regards,
>
> Michael.
Thanks a lot,
--
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University
next prev parent reply other threads:[~2015-06-25 18:06 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-25 17:09 How the backquote and the comma really work? Marcin Borkowski
2015-06-25 17:33 ` Michael Heerdegen
2015-06-25 18:06 ` Marcin Borkowski [this message]
2015-06-25 18:22 ` Michael Heerdegen
2015-06-25 18:39 ` Marcin Borkowski
2015-06-25 18:44 ` Marcin Borkowski
2015-06-25 19:06 ` Michael Heerdegen
2015-07-10 11:36 ` Marcin Borkowski
2015-07-12 15:54 ` Michael Heerdegen
2015-07-12 19:55 ` Marcin Borkowski
2015-07-12 20:33 ` Marcin Borkowski
2015-07-14 18:17 ` Marcin Borkowski
2015-07-14 22:08 ` Emanuel Berg
2015-07-21 22:08 ` Michael Heerdegen
2015-07-24 13:01 ` Michael Heerdegen
2015-08-11 11:41 ` Marcin Borkowski
2015-08-12 15:29 ` Michael Heerdegen
[not found] ` <mailman.8207.1439393377.904.help-gnu-emacs@gnu.org>
2015-08-12 16:30 ` Pascal J. Bourguignon
2015-08-23 8:30 ` Marcin Borkowski
[not found] ` <mailman.110.1440318650.11330.help-gnu-emacs@gnu.org>
2015-08-23 16:46 ` Pascal J. Bourguignon
2015-07-21 21:54 ` Michael Heerdegen
2015-08-11 10:15 ` Marcin Borkowski
2015-08-11 17:20 ` Thorsten Jolitz
2015-08-12 15:01 ` Michael Heerdegen
2015-07-21 21:50 ` Michael Heerdegen
2015-06-25 18:10 ` Drew Adams
2015-06-25 18:40 ` Michael Heerdegen
2015-06-25 18:53 ` Marcin Borkowski
2015-06-25 19:39 ` Michael Heerdegen
2015-06-25 20:05 ` Drew Adams
2015-06-25 20:18 ` Marcin Borkowski
2015-06-25 20:37 ` Drew Adams
2015-06-25 23:55 ` Robert Thorpe
[not found] ` <mailman.5697.1435276533.904.help-gnu-emacs@gnu.org>
2015-06-26 1:41 ` Rusi
2015-06-26 14:24 ` Michael Heerdegen
[not found] ` <mailman.5716.1435328741.904.help-gnu-emacs@gnu.org>
2015-06-26 14:35 ` Rusi
2015-06-26 14:51 ` Michael Heerdegen
2015-06-25 18:46 ` Marcin Borkowski
2015-06-26 7:31 ` tomas
2015-06-26 13:48 ` Drew Adams
2015-06-26 14:06 ` tomas
2015-06-26 15:06 ` Emanuel Berg
2015-07-12 17:38 ` Vaidheeswaran C
[not found] <mailman.5657.1435252169.904.help-gnu-emacs@gnu.org>
2015-06-30 16:27 ` sokobania.01
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/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87si9ffys0.fsf@mbork.pl \
--to=mbork@mbork.pl \
--cc=help-gnu-emacs@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).