From: Joost Kremers <joostkremers@fastmail.fm>
To: steve-humphreys@gmx.com
Cc: help-gnu-emacs@gnu.org
Subject: Re: Understanding the "let" construct and the setting of variables
Date: Thu, 17 Dec 2020 09:56:12 +0100 [thread overview]
Message-ID: <87a6uc244a.fsf@fastmail.fm> (raw)
In-Reply-To: <trinity-d74515d5-16ba-4b28-a7df-932aa5fe68b9-1608194610119@3c-app-mailcom-bs11>
On Thu, Dec 17 2020, steve-humphreys@gmx.com wrote:
> This gets me to "defvar". I have read that "setq" does net actually
> make a variable. It is defvar that makes a variable available.
`defvar` creates a global variable, yes. `setq` creates a global variable if the
variable does not exist yet. So if you do:
```
(let ((a (some-value)))
(do-something)
(setq a (some-value-based-on a))
(do-something-else))
```
Then setq updates the local binding for `a`. If you use setq on a variable that
doesn't have a local binding (i.e., isn't bound in the let that contains the
setq), it creates a new, global binding.
> Do the question really is this. What happens when one sets an object with "setq"
> if elisp does not make a variable from the name?
Not sure I understand the question. With `setq`, two things can happen: either
there is already a binding for the variable, in which case `setq` updates the
binding (assigns a new value to the existing variable), or there is no such
binding (i.e., the variable doesn't exist), and in that case the variable is created.
--
Joost Kremers
Life has its moments
next prev parent reply other threads:[~2020-12-17 8:56 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 0:10 Understanding the "let" construct and the setting of variables steve-humphreys
2020-12-17 0:21 ` Joost Kremers
2020-12-17 2:08 ` steve-humphreys
2020-12-17 3:12 ` steve-humphreys
2020-12-17 8:01 ` Joost Kremers
2020-12-17 8:31 ` steve-humphreys
2020-12-17 8:50 ` Joost Kremers
2020-12-17 8:10 ` Joost Kremers
2020-12-17 8:43 ` steve-humphreys
2020-12-17 8:56 ` Joost Kremers [this message]
2020-12-18 20:48 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-18 20:46 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-18 21:07 ` Jean Louis
2020-12-18 22:31 ` tomas
2020-12-18 20:39 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-17 2:49 ` steve-humphreys
2020-12-17 7:58 ` Joost Kremers
2020-12-17 16:55 ` Drew Adams
2020-12-17 20:11 ` steve-humphreys
2020-12-17 21:57 ` Drew Adams
2020-12-17 22:35 ` Michael Heerdegen
2020-12-18 9:01 ` tomas
2020-12-18 9:16 ` Michael Heerdegen
2020-12-18 20:55 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-19 2:17 ` Michael Heerdegen
2020-12-19 2:52 ` Drew Adams
2020-12-19 5:15 ` Stefan Monnier
2020-12-18 20:33 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-17 0:25 ` steve-humphreys
2020-12-17 0:35 ` steve-humphreys
2020-12-17 1:05 ` Joost Kremers
2020-12-17 1:20 ` steve-humphreys
2020-12-18 20:58 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-17 4:34 ` Jean Louis
2020-12-17 5:12 ` steve-humphreys
2020-12-19 6:06 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-17 7:31 ` steve-humphreys
2020-12-19 5:55 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-19 6:49 ` Jean Louis
2020-12-20 5:19 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-18 17:14 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-18 17:48 ` tomas
2020-12-18 15:33 ` Emanuel Berg via Users list for the GNU Emacs text editor
2020-12-18 18:12 ` Jean Louis
2020-12-18 18:20 ` Drew Adams
2020-12-18 18:45 ` Jean Louis
2020-12-18 19:16 ` Drew Adams
2020-12-18 20:00 ` Jean Louis
2020-12-18 21:27 ` Christopher Dimech
2020-12-19 6:23 ` Emanuel Berg via Users list for the GNU Emacs text editor
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