From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Philipp <p.stephani2@gmail.com>
Cc: help-gnu-emacs@gnu.org
Subject: Re: Which Elisp types are mutable?
Date: Mon, 05 Jul 2021 16:19:29 -0400 [thread overview]
Message-ID: <jwveeccwmgr.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <92E21250-DE31-4637-97A6-63E2C1C719A8@gmail.com> (Philipp's message of "Mon, 5 Jul 2021 20:40:01 +0200")
Philipp [2021-07-05 20:40:01] wrote:
>> Am 05.06.2021 um 16:25 schrieb Stefan Monnier via Users list for the GNU
>> Emacs text editor <help-gnu-emacs@gnu.org>:
>>> "You must not mutate them" is the definition of immutable.
>> Not necessarily: where I come from "immutable" means that the object
>> cannot and will not be mutated.
> Then there are no immutable objects, because all objects are stored in
> mutable memory.
You're confusing a language and its implementation.
E.g. ELisp bytecode objects are immutable vectors. Technically there is
some potential way to mutate them because they're stored in the normal
mutable memory, but efforts were made so that ELisp code cannot
mutate them.
For the same reason, ELisp code cannot "transmute" a marker into an
overlay, even though nothing stops you from doing it at the C level.
> So this definition of "immutable" isn't very useful.
I think most language designers would beg to differ.
Stefan
next prev parent reply other threads:[~2021-07-05 20:19 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-03 4:03 Which Elisp types are mutable? Marcin Borkowski
2021-06-03 12:11 ` Philipp
2021-06-05 11:22 ` Marcin Borkowski
2021-06-05 12:58 ` Philipp
2021-06-05 14:25 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-07-05 18:40 ` Philipp
2021-07-05 20:19 ` Stefan Monnier [this message]
2021-07-05 20:44 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-07-05 20:58 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-07-05 21:03 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-05 19:19 ` Marcin Borkowski
2021-06-05 20:17 ` [External] : " Drew Adams
2021-06-05 20:36 ` Dmitry Gutov
2021-06-06 1:57 ` Drew Adams
2021-07-05 18:41 ` Philipp
2021-07-05 18:48 ` Eli Zaretskii
2021-07-05 18:55 ` tomas
2021-07-05 19:26 ` [External] : " Drew Adams
2021-07-05 19:40 ` tomas
2021-07-05 20:03 ` Drew Adams
2021-07-05 20:12 ` tomas
2021-07-05 20:39 ` Drew Adams
2021-07-05 20:58 ` Emanuel Berg via Users list for the GNU Emacs text editor
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