GNU bug report logs - #62020
Lisp reader: dotted pair notation not working when initial elements are omitted

Previous Next

Full log

Message #8 received at 62020 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Federico Tedin <federicotedin <at> gmail.com>,
 Mattias Engdegård <mattiase <at> acm.org>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 62020 <at> debbugs.gnu.org
Subject: Re: bug#62020: Lisp reader: dotted pair notation not working when
 initial elements are omitted
Date: Tue, 07 Mar 2023 14:53:59 +0200

> From: Federico Tedin <federicotedin <at> gmail.com>
> Date: Tue, 7 Mar 2023 02:14:02 +0100
> 
> According to the Elisp docs
> (https://www.gnu.org/software/emacs/manual/html_node/elisp/Dotted-Pair-Notation.html),
> one should be able to evaluate e.g.:
>     (. 1)
> to:
>     1
> 
> This works correctly in Emacs 28.1 However, in the emacs-29 branch
> (bd07cec) this results in:
>     *** Read error ***  Invalid read syntax: "."
> 
> Since the description in the docs are the same in the emacs-29 I
> assume this is a bug.
> I believe this may have been caused by the changes implementing the
> nonrecursive Lisp reader.
> I believe the fix would be roughly:
> - in read0 (lread.c), when handling c == '.', ensure we handle not
> only the case where the top of the read stack is RE_list but *also*
> RE_list_start.
> - if the top of the stack was effectively RE_list_start, then the top
> of the stack needs to be manipulated somehow so that at the end of
> read0 the correct value is returned, when emptying the stack.

Stefan and Mattias, can you please see how to fix this regression?

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.