GNU bug report logs - #79320
30.2; Doc of `dolist'

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Drew Adams <drew.adams <at> oracle.com>
To: "bug-gnu-emacs <at> gnu.org" <bug-gnu-emacs <at> gnu.org>
Subject: 30.2; Doc of `dolist'
Date: Tue, 26 Aug 2025 19:49:42 +0000

Minor enhancement request.

I believe it's the case that the first arg to `dolist' can be a defvar
(special/dynamic variable).

Grepping shows that this is _very rarely_ done.  I gave up scanning a
full grep of the Emacs sources - I came across _only_ `apropos-item' as
a defvar: (dolist (apropos-item p) ...)

It's possible that users aren't aware of this possibility, and if they
were then their code could sometimes be a bit simpler.  E.g., instead of
this:

(let ((v  my-defvar))
  (dolist (v  some-list)
     (setq my-defvar  v)
     ...))

They can do this: (dolist (my-defvar  some-list) ...).

Maybe it would be good to point out in the doc that the VAR argument can
be either a lexical variable or a dynamic variable.

The same could be said for other, similar macros, such as `dotimes'.

The doc does say that VAR is bound..., so it doesn't say it _can't_ be a
dynamic variable.  But maybe it would help to make this clearer.


In GNU Emacs 30.2 (build 2, x86_64-w64-mingw32) of 2025-08-14 built on
 AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.26100
System Description: Microsoft Windows 10 Pro (v10.0.2009.26100.4652)

Configured using:
 'configure --with-modules --without-dbus --with-native-compilation=aot
 --without-compress-install --with-tree-sitter CFLAGS=-O2
 prefix=/g/rel/install-emacs-30.2'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XPM ZLIB

(NATIVE_COMP present but libgccjit not available)

Message #8 received at 79320 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Drew Adams <drew.adams <at> oracle.com>
Cc: 79320 <at> debbugs.gnu.org
Subject: Re: bug#79320: 30.2; Doc of `dolist'
Date: Wed, 27 Aug 2025 14:36:39 +0300

> Date: Tue, 26 Aug 2025 19:49:42 +0000
> From:  Drew Adams via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
> 
> Minor enhancement request.
> 
> I believe it's the case that the first arg to `dolist' can be a defvar
> (special/dynamic variable).
> 
> Grepping shows that this is _very rarely_ done.  I gave up scanning a
> full grep of the Emacs sources - I came across _only_ `apropos-item' as
> a defvar: (dolist (apropos-item p) ...)

Where does the documentation say that the first argument to dolist
_cannot_ be a dynamically-bounded variable?

Message #11 received at 79320 <at> debbugs.gnu.org (full text, mbox):

From: Drew Adams <drew.adams <at> oracle.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: "79320 <at> debbugs.gnu.org" <79320 <at> debbugs.gnu.org>
Subject: RE: [External] : Re: bug#79320: 30.2; Doc of `dolist'
Date: Wed, 27 Aug 2025 14:24:54 +0000

> Where does the documentation say that the first argument to dolist
> _cannot_ be a dynamically-bounded variable?

I already said that it does not say that.  It correctly
says that "VAR is bound...".  The point is that it might
not be obvious that VAR can be a defvar; that's all.

That users might not be aware of this isn't the end of
the world.  But it wouldn't hurt to point it out. 

Message #14 received at 79320 <at> debbugs.gnu.org (full text, mbox):

From: Richard Stallman <rms <at> gnu.org>
To: Drew Adams <drew.adams <at> oracle.com>
Cc: eliz <at> gnu.org, 79320 <at> debbugs.gnu.org
Subject: Re: bug#79320: 30.2; Doc of `dolist'
Date: Fri, 29 Aug 2025 21:59:28 -0400

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > I already said that it does not say that.  It correctly
  > says that "VAR is bound...".  The point is that it might
  > not be obvious that VAR can be a defvar; that's all.

I agree it would be good to say this explicitly.
Explaining consequences that are not obvious
is part of what makes for a good manual.

Thanks for the suggestion.

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)

Message #17 received at 79320 <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 79320 <at> debbugs.gnu.org, Drew Adams <drew.adams <at> oracle.com>
Subject: Re: bug#79320: 30.2; Doc of `dolist'
Date: Tue, 02 Sep 2025 15:35:50 +0200

Eli Zaretskii <eliz <at> gnu.org> writes:

> Where does the documentation say that the first argument to dolist
> _cannot_ be a dynamically-bounded variable?

It's not absolutely trivial what the semantics are.  It could be that
dolist always created a fresh lexical variable VAR of the same name
(although the docstring rather suggests that dolist directly uses the
given variable, and not some new variable of the same name of any kind).

Anyway, like Richard I think it could be good to add a hint nonetheless
because the fact and its consequences are probably not obvious to a lot
of users.


Michael.

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