From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.help Subject: Re: How the backquote and the comma really work? Date: Thu, 25 Jun 2015 19:33:16 +0200 Message-ID: <87r3ozy9pf.fsf@web.de> References: <87vbebg1fs.fsf@mbork.pl> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1435253652 6245 80.91.229.3 (25 Jun 2015 17:34:12 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 25 Jun 2015 17:34:12 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Jun 25 19:33:54 2015 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Z8B29-0001ri-Mj for geh-help-gnu-emacs@m.gmane.org; Thu, 25 Jun 2015 19:33:53 +0200 Original-Received: from localhost ([::1]:56808 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z8B29-0007tK-66 for geh-help-gnu-emacs@m.gmane.org; Thu, 25 Jun 2015 13:33:53 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:39370) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z8B1q-0007q5-6s for help-gnu-emacs@gnu.org; Thu, 25 Jun 2015 13:33:34 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z8B1m-0001OG-Hw for help-gnu-emacs@gnu.org; Thu, 25 Jun 2015 13:33:33 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:39022) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z8B1m-0001NR-3G for help-gnu-emacs@gnu.org; Thu, 25 Jun 2015 13:33:30 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1Z8B1j-0001SY-0E for help-gnu-emacs@gnu.org; Thu, 25 Jun 2015 19:33:27 +0200 Original-Received: from ip-90-186-253-113.web.vodafone.de ([90.186.253.113]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 25 Jun 2015 19:33:26 +0200 Original-Received: from michael_heerdegen by ip-90-186-253-113.web.vodafone.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 25 Jun 2015 19:33:26 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 40 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: ip-90-186-253-113.web.vodafone.de User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) Cancel-Lock: sha1:R5YakMsB0zHFMKk9P/iwkX6viQE= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:105161 Archived-At: Marcin Borkowski 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 It's also a reader macro so that you can write `thing as an abbreviation of of (` thing) but that's just a detail. > 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 ;-) Regards, Michael.