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bug#25929: 25.2; map-delete doesn't delete permanently 1st alist elt
From: |
Richard Stallman |
Subject: |
bug#25929: 25.2; map-delete doesn't delete permanently 1st alist elt |
Date: |
Wed, 27 Apr 2022 23:17:20 -0400 |
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> > *) It happens just for alist, other maps are fine.
> (I'm going through old bug reports that unfortunately weren't resolved
> at the time.)
> Various things were proposed here, but they all had problems. So I
> don't think there's much to be done here except documenting this, which
> I've now done in Emacs 29.
It is a natural consequence of list structure that deleting the first element
doesn't do it destructively, so you need to do
(setq foo (delq elt foo))
This is a general principal of deletion in Lisp, so let's teach it to
people rather than trying to help people avoid the need to learn it.
--
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)