From: Philip Kaludercic <philipk@posteo.net>
To: "Basil L. Contovounesios" <basil@contovou.net>
Cc: Felician Nemeth <felician.nemeth@gmail.com>, emacs-devel@gnu.org
Subject: Re: (byte-compile '(append '(1 2) '(3 4)))
Date: Sat, 16 Mar 2024 13:55:52 +0000 [thread overview]
Message-ID: <875xxmb7rr.fsf@posteo.net> (raw)
In-Reply-To: <87wmq2nweb.fsf@epfl.ch> (Basil L. Contovounesios's message of "Sat, 16 Mar 2024 14:23:08 +0100")
"Basil L. Contovounesios" <basil@contovou.net> writes:
> Philip Kaludercic [2024-03-16 12:46 +0000] wrote:
>
>> I am not sure what the danger is in the case of constant, quoted lists,
>> but I am not familiar with the byte compiler either. It seems like this
>>
>> diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
>> index f75be3f71ad..e6f18590705 100644
>> --- a/lisp/emacs-lisp/byte-opt.el
>> +++ b/lisp/emacs-lisp/byte-opt.el
>> @@ -1599,6 +1599,12 @@ byte-optimize-append
>> (cdr args))
>> (cdr newargs)))
>>
>> + ;; (append '(C1...) ... '(C2...)) -> (append C1... ... C2...)
>> + ((cl-loop for arg in args
>> + always (and (eq (car arg) 'quote)
>> + (proper-list-p (cdr arg))))
>> + `',(mapcan #'cadr args))
>> +
>> ;; non-terminal arg
>> ((cdr args)
>> (cond
>>
>>
>> would do the trick, and the byte-code is even better:
>>
>> byte code:
>> args: nil
>> 0 constant (1 2 3 4)
>> 1 return
>
> Is this correct? According to its docstring, append's last argument
> must be eq to the tail of its return value.
This little test indicates that it would still be eq:
((macro . (lambda (arg)
`(eq (cddadr (byte-optimize-append '(append '(1 2) ,arg)))
,arg)))
'(3 4)) ;=> t
since the mapcan or rather nconc makes the same promise.
--
Philip Kaludercic on peregrine
next prev parent reply other threads:[~2024-03-16 13:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87v8j28c2x.fsf@betli.tmit.bme.hu>
[not found] ` <874jdipfp5.fsf@posteo.net>
[not found] ` <87cys6t734.fsf@betli.tmit.bme.hu>
[not found] ` <87r0gmnjq4.fsf@posteo.net>
[not found] ` <87o7bprr04.fsf@betli.tmit.bme.hu>
[not found] ` <87bk7p57yz.fsf@posteo.net>
2024-03-16 12:16 ` (byte-compile '(append '(1 2) '(3 4))) Felician Nemeth
2024-03-16 12:46 ` Philip Kaludercic
2024-03-16 13:23 ` Basil L. Contovounesios
2024-03-16 13:45 ` Felician Nemeth
2024-03-16 13:55 ` Philip Kaludercic [this message]
2024-03-16 23:42 ` Basil L. Contovounesios
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=875xxmb7rr.fsf@posteo.net \
--to=philipk@posteo.net \
--cc=basil@contovou.net \
--cc=emacs-devel@gnu.org \
--cc=felician.nemeth@gmail.com \
/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.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/emacs.git
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).