From: Marcin Borkowski <mbork@mbork.pl>
To: Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
Subject: How the backquote and the comma really work?
Date: Thu, 25 Jun 2015 19:09:11 +0200 [thread overview]
Message-ID: <87vbebg1fs.fsf@mbork.pl> (raw)
Hi all,
I decided that the time has come that I finally approach the scary
backquote-comma duo. (While I understand it superficially, I’d like to
get it right and thoroughly this time.) So my question is whether my
mental model (see below) is correct.
So, I assume that when Emacs Lisp interpreter encounters a backquote, it
looks at the expression after it. If it is anything but a list, it just
works like the usual quote, and the backquoted expression evaluates to
what was backquoted.
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? (I am aware that I didn’t take
into account the splicing operator, but it doesn’t introduce a lot of
additional complexity) Of course, when writing it, I realized that my
natural-language description is not extremely precise, so a bonus
question is: can I find an Emacs Lisp metacircular evaluator (taking
into account the quoting mechanisms) anywhere?
And I know that I risk starting another thread lasting for dozens of
messages;-) – but I /do/ want to understand this stuff... In fact, in
the spirit of another recent discussion, I want to write a simple code
analyzer, finding one-legged ‘if’s and suggesting replacing them with
‘when’s or ‘unless’es. This is trivial unless (pun intended) you want
to take (back)quotes into consideration.
Best regards,
--
Marcin Borkowski This email was proudly sent
http://mbork.pl from my Emacs.
next reply other threads:[~2015-06-25 17:09 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-25 17:09 Marcin Borkowski [this message]
2015-06-25 17:33 ` How the backquote and the comma really work? Michael Heerdegen
2015-06-25 18:06 ` Marcin Borkowski
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
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