From: Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>
To: help-gnu-emacs@gnu.org
Subject: Re: Understanding the "let" construct and the setting of variables
Date: Fri, 18 Dec 2020 21:39:52 +0100 [thread overview]
Message-ID: <871rfmzw4n.fsf@zoho.eu> (raw)
In-Reply-To: 87o8is26nu.fsf@fastmail.fm
Joost Kremers wrote:
>> QUESTION: What happens if one does a "setq" on a variable
>> defined in the binding part of the "let"? Can one do that?
>
> Yes, inside the body of the `let`, you can.
You can, but it isn't optimal because if you make a typo you
will be unaware of it and instead a global variable will
silently be created. If it already exist, oh, my you will
modify that instead of the intended let binding variable.
So better to do all computation you reasonably can _before_
the let body, already in the varlist.
Use several steps with `let*' and add supposedly unnecessary
steps for clarity, better access and easier debug.
In the let body, optimally, all computation is already done.
There, you just _do_ whatever it is should happen, using the
values you already have for the purpose.
--
underground experts united
http://user.it.uu.se/~embe8573
https://dataswamp.org/~incal
next prev parent reply other threads:[~2020-12-18 20:39 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=871rfmzw4n.fsf@zoho.eu \
--to=help-gnu-emacs@gnu.org \
--cc=moasenwood@zoho.eu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.