GNU bug report logs - #40671
[DOC] modify literal objects

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Package: emacs;

Reported by: Kevin Vigouroux <ke.vigouroux <at> laposte.net>

Date: Thu, 16 Apr 2020 20:40:02 UTC

Severity: normal

Tags: patch

Done: Paul Eggert <eggert <at> cs.ucla.edu>

Bug is archived. No further changes may be made.

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From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Mattias Engdegård <mattiase <at> acm.org>, Richard Stallman <rms <at> gnu.org>
Cc: Michael Heerdegen <michael_heerdegen <at> web.de>, ke.vigouroux <at> laposte.net, eggert <at> cs.ucla.edu, 40671 <at> debbugs.gnu.org
Subject: bug#40671: [DOC] modify literal objects
Date: Fri, 24 Apr 2020 19:46:38 +0300

On 24.04.2020 19:39, Mattias Engdegård wrote:
> That is an interesting point. What is the difference between CANNOT and SHOULD NOT, operationally? To the user, nothing; there is no gain from disobeying our advice.

The difference is at runtime, obviously. And the problem is using the 
words in a way that differs from other programming languages, for instance.

> It's useful to have the option to add strong checks, so that (setcar '(1 . 2) 3) throws an error. Then, what used to be SHOULD NOT turns into CANNOT, but the attentive user has no reason to change behaviour.

*If* we do that, we could call them constants. But I imagine we never 
will, for backward compatibility reasons. Emacs core itself modifies 
these "constants" at runtime in quite a few places, I'm sure.
This bug report was last modified 5 years and 56 days ago.

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