From: Philip Kaludercic <philipk@posteo.net>
To: Yuri Khan <yuri.v.khan@gmail.com>
Cc: help-gnu-emacs <help-gnu-emacs@gnu.org>
Subject: Re: Appending lists
Date: Wed, 16 Jun 2021 13:01:10 +0000 [thread overview]
Message-ID: <87im2eufop.fsf@posteo.net> (raw)
In-Reply-To: <YMng65cpd/RhXSs6@protected.localdomain> (Jean Louis's message of "Wed, 16 Jun 2021 14:30:51 +0300")
Jean Louis <bugs@gnu.support> writes:
> * Yuri Khan <yuri.v.khan@gmail.com> [2021-06-16 14:18]:
>> On Wed, 16 Jun 2021 at 16:35, Jean Louis <bugs@gnu.support> wrote:
>>
>> > What is it doing in background, or underground, does not really matter
>> > for user, what matters is that `x' in following example is changed:
>>
>> See, that’s your problem: You think there *is* an underground.
>>
>> Lisp starts with symbols and cons cells and that’s the ground level.
>> It then builds up from that to lists and trees and associative lists.
>> And when you have an associative list binding a symbol to a value,
>> that’s when you get variables, some three floors above the ground.
>
> That is why I leave that to engineers like you. You see, today my
> friend was mentioning how he does not like one but the other webmail
> system. He has no clue about the underlying software, what he wants it
> functionality.
>
>> And then, when you invoke ‘nreverse’ on a list pointed to by a
>> variable, you, from high up above, can see it scurrying down there and
>> re-routing the ‘cdr’s of the cons cells comprising the list, but not
>> touching the one link from the variable to whatever cons cell had been
>> the first in the list.
>
> I like your smartness, though I would like to have more practical use
> of it. Thomas said that `nconc' does not change `list', unless it is
> special form. And I can practically see this:
>
> (setq list '(A B C)) ⇒ (A B C)
> (nconc list '(1 2 3)) ⇒ (A B C 1 2 3)
> list ⇒ (A B C 1 2 3)
Change that to
(let* ((list-1 '(a b c))
(list-2 (nconc list-1 '(1 2 3))))
(eq list-1 list-2)) ;; => t
and the point should be obvious. This is a confusion on a superficial
level, just like how beginners in C-like languages find it weird that
you can write something like
x = x + 1
> So maybe he was thinking that symbol `list' does not change, and I
> understood it that variable value does not change.
>
> Why not come back to that and explain me how the variable `list' did
> not change from (A B C) to (A B C 1 2 3)?
--
Philip K.
next prev parent reply other threads:[~2021-06-16 13:01 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 16:36 Appending lists Pierpaolo Bernardi
2021-06-14 16:40 ` henri-biard
2021-06-14 18:21 ` Alexandr Vityazev
2021-06-15 0:46 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-15 8:27 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-15 9:18 ` tomas
2021-06-16 1:11 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 7:28 ` tomas
2021-06-16 9:13 ` Jean Louis
2021-06-16 9:32 ` tomas
2021-06-16 10:55 ` Jean Louis
2021-06-16 16:44 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 18:00 ` Using Emacs for business Jean Louis
2021-06-16 22:59 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 23:39 ` Jean Louis
2021-06-17 0:16 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-17 7:09 ` Jean Louis
2021-07-06 3:22 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-07-06 20:23 ` Jean Louis
2021-07-06 20:41 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-07-07 0:18 ` Jean Louis
2021-06-16 9:19 ` Appending lists Jean Louis
2021-06-16 9:35 ` tomas
2021-06-16 10:57 ` Jean Louis
2021-06-16 16:55 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 11:16 ` Yuri Khan
2021-06-16 11:30 ` Jean Louis
2021-06-16 11:54 ` tomas
2021-06-16 17:31 ` Jean Louis
2021-06-16 23:13 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 23:41 ` Jean Louis
2021-06-16 13:01 ` Philip Kaludercic [this message]
2021-06-16 16:59 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 17:36 ` Jean Louis
2021-06-16 18:54 ` tomas
2021-06-16 21:24 ` Philip Kaludercic
2021-06-16 23:25 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-17 7:16 ` tomas
2021-06-17 7:14 ` tomas
2021-06-16 23:24 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 23:19 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 11:49 ` [OT] Underground (was: Appending lists) tomas
2021-06-19 0:10 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 16:54 ` Appending lists Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 18:49 ` tomas
2021-06-16 21:40 ` Jean Louis
2021-06-16 22:35 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-16 23:02 ` Jean Louis
2021-06-17 0:00 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 23:44 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-17 7:20 ` tomas
2021-06-16 23:39 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 23:31 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 14:22 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-16 15:11 ` tomas
2021-06-16 15:31 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-16 15:48 ` tomas
2021-06-16 23:04 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-17 2:41 ` [OFFTOPIC] " Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-17 6:09 ` Arthur Miller
2021-06-17 6:29 ` Stefan Monnier
2021-06-17 23:53 ` Arthur Miller
2021-06-18 14:15 ` Stefan Monnier
2021-06-19 0:04 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-19 1:20 ` Eduardo Ochs
2021-06-19 2:18 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-19 2:43 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-21 15:07 ` Arthur Miller
2021-06-17 7:51 ` tomas
2021-06-17 7:50 ` tomas
2021-06-18 23:47 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-19 2:35 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-19 6:52 ` tomas
2021-06-16 23:03 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 16:42 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 16:55 ` [External] : " Drew Adams
2021-06-16 17:06 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-16 17:54 ` Drew Adams
2021-06-16 23:49 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-17 7:54 ` tomas
2021-06-17 12:41 ` [OFFTOPIC] " Stefan Monnier via Users list for the GNU Emacs text editor
2021-06-17 14:19 ` tomas
2021-06-18 23:55 ` [External] : " Emanuel Berg via Users list for the GNU Emacs text editor
-- strict thread matches above, loose matches on Subject: below --
2021-06-17 3:18 Drew Adams
2021-06-17 7:48 ` tomas
2021-06-18 23:38 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-18 23:50 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-19 6:57 ` tomas
2021-06-19 21:31 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-14 16:44 Pierpaolo Bernardi
2021-06-15 0:56 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-15 1:47 ` henri-biard
2021-06-15 7:09 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-06-14 16:24 Pierpaolo Bernardi
2021-06-14 16:32 ` henri-biard
2021-06-14 16:08 henri-biard
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