From: Emanuel Berg <embe8573@student.uu.se>
To: help-gnu-emacs@gnu.org
Subject: Re: Always using let*
Date: Sun, 14 Sep 2014 23:41:49 +0200 [thread overview]
Message-ID: <87d2axg9r6.fsf@debian.uxu> (raw)
In-Reply-To: mailman.8868.1410729956.1147.help-gnu-emacs@gnu.org
Drew Adams <drew.adams@oracle.com> writes:
>> Would it be OK to always use let*? I was just bitten
>> by the fact that with let you can not previous
>> variables from the let statement, as is possible
>> with setq. So I am thinking about always using let*,
>> so I do not have to think about it. Or are there
>> good reasons to use let when you do not need let*?
>
> The most common reason is when you want to use a
> variable value in the cadr of a binding and you do
> *not* want to pick up the variable's newly bound
> value. IOW, precisely the opposite use case of what
> you wanted when you were bit.
>
> (setq c 3)
>
> (let ((c (+ c 4)) (b (* c 42)))
Correct, but isn't that only confusing style?
Isn't it better to call the c in the let something
else?
The only reason I don't always use let* is that it is
slower type, looks awkward, and that other people
reading the code will wonder: "why `let*'? there is
nothing reoccurring!"
> (The other reason is that for some Lisps the bindings
> of `let' can be done in parallel, which can be
> quicker.)
Oh yeah?! Like parallel on a multicore computer? I only
have single CPU so I can't test but that would be
downright awesome.
However let* could also in part run in parallel for the
clauses that don't have precedence constraints (i.e.,
for wich the let* isn't necessary).
--
underground experts united
next prev parent reply other threads:[~2014-09-14 21:41 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-14 19:46 Always using let* Cecil Westerhof
2014-09-14 21:25 ` Drew Adams
2014-09-15 16:15 ` Drew Adams
[not found] ` <mailman.8924.1410797740.1147.help-gnu-emacs@gnu.org>
2014-09-15 18:01 ` Cecil Westerhof
2014-09-15 22:20 ` Emanuel Berg
2014-09-16 12:05 ` Cecil Westerhof
2014-09-16 22:40 ` Emanuel Berg
2014-09-18 17:02 ` Cecil Westerhof
2014-09-18 21:05 ` Emanuel Berg
2014-09-16 14:23 ` sokobania.01
2014-09-16 16:41 ` Drew Adams
2014-09-16 20:49 ` Stefan Monnier
2014-09-16 22:45 ` Emanuel Berg
[not found] ` <mailman.8998.1410901776.1147.help-gnu-emacs@gnu.org>
2014-09-16 22:48 ` Emanuel Berg
2014-09-17 1:09 ` Stefan Monnier
2014-09-17 1:18 ` Emanuel Berg
2014-09-14 21:40 ` Joe Fineman
[not found] ` <mailman.8868.1410729956.1147.help-gnu-emacs@gnu.org>
2014-09-14 21:41 ` Emanuel Berg [this message]
2014-09-14 22:11 ` Cecil Westerhof
2014-09-14 22:56 ` Drew Adams
2014-09-14 22:41 ` Stefan Monnier
2014-09-14 23:06 ` Drew Adams
[not found] ` <mailman.8871.1410736002.1147.help-gnu-emacs@gnu.org>
2014-09-15 0:47 ` Emanuel Berg
2014-09-15 2:12 ` Pascal J. Bourguignon
2014-09-15 2:22 ` Stefan Monnier
2014-09-15 2:59 ` Pascal J. Bourguignon
2014-09-15 12:31 ` Stefan Monnier
2014-09-15 16:15 ` Drew Adams
2014-09-15 19:05 ` Stefan Monnier
[not found] ` <mailman.8930.1410808006.1147.help-gnu-emacs@gnu.org>
2014-09-15 22:28 ` Emanuel Berg
2014-09-16 0:38 ` Pascal J. Bourguignon
2014-09-15 13:14 ` Barry Margolin
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
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87d2axg9r6.fsf@debian.uxu \
--to=embe8573@student.uu.se \
--cc=help-gnu-emacs@gnu.org \
/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.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).