From: Emanuel Berg <embe8573@student.uu.se>
To: help-gnu-emacs@gnu.org
Subject: Re: What does "lacks a prefix" mean?
Date: Sun, 12 Jul 2015 00:42:54 +0200 [thread overview]
Message-ID: <87zj32pb81.fsf@nl106-137-147.student.uu.se> (raw)
In-Reply-To: jwvd200q794.fsf-monnier+gmane.emacs.help@gnu.org
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> let* says "I need variables which depend on each
>> other" and if they're really not, that
>> look strange.
>
> If let behaved like let* it wouldn't look strange to
> you. Many other functional languages dropped the
> "simultaneous let" and only kept the equivalent of
> let* (or even letrec).
>
>> And probably it's a bit slower.
>
> Regarding efficiency, there's no clear winner
> between the two. It's basically irrelevant.
>
>> And non-parallelizable theoretically :)
>
> In practice neither is easily parallelizable anyway.
> And the work needed to auto-convert a "let*" to
> a "let" when possible is trivial in comparison to
> what's needed to parallelize the code. So again,
> it's really irrelevant.
Hear? I couldn't have said it better myself. Wait...
I couldn't! But let me say a couple of other things:
1) "let" looks better and is faster to type, both in
terms of the number of chars used and what those
chars are (i.e., no "*" in "let" which is only
normal letters).
2) With the let/let* distinction, while let* being the
oddball, it sends the signal that the "let" style,
and not the one of "let*", is the one preferred.
But it is actually the "let*" style that should be
favored! It is much more clear and
easily navigated. Compare:
(setq side 3.0)
(let ((cube-volume (* side side side)))
cube-volume)
vs.
(let* ((side 3.0)
(side-area (* side side))
(cube-volume (* side-area side)) )
cube-volume)
"Dependencies" are the most natural things and
aren't anything to be afraid of! Only if you are
the manager of a Linux distro they can get out of
hands sometimes...
3) "let", if let was let*, would be less thinking in
advance since then you wouldn't have to think "so,
will I have variables now which will depend on
each other?" You'd just type "let" in either case!
Likewise, when you modify code long after you
first wrote it, you often insert a new variable
that is "dependent" on another, and then you have
to change the `let' to `let*'. But this is very
easy to forget and it is always a silly mistake
when it happens.
--
underground experts united
http://user.it.uu.se/~embe8573
next prev parent reply other threads:[~2015-07-11 22:42 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-08 16:32 What does "lacks a prefix" mean? BobD
2015-07-08 16:45 ` Barry Margolin
2015-07-08 16:59 ` Vaidheeswaran C
2015-07-08 17:10 ` Vaidheeswaran C
2015-07-08 18:17 ` BobD
2015-07-08 18:21 ` Pascal J. Bourguignon
2015-07-08 18:45 ` BobD
2015-07-08 23:24 ` Emanuel Berg
2015-07-09 15:23 ` Filipp Gunbin
2015-07-09 22:32 ` Emanuel Berg
2015-07-10 17:04 ` Stefan Monnier
2015-07-11 22:42 ` Emanuel Berg [this message]
[not found] ` <mailman.6748.1436654668.904.help-gnu-emacs@gnu.org>
2015-07-11 23:58 ` Barry Margolin
2015-07-13 12:26 ` Filipp Gunbin
[not found] ` <mailman.6685.1436547891.904.help-gnu-emacs@gnu.org>
2015-07-10 18:27 ` Barry Margolin
[not found] ` <mailman.6612.1436455429.904.help-gnu-emacs@gnu.org>
2015-07-09 23:27 ` Barry Margolin
[not found] ` <mailman.6643.1436488423.904.help-gnu-emacs@gnu.org>
2015-07-10 0:49 ` Pascal J. Bourguignon
2015-07-10 5:04 ` Drew Adams
2015-07-10 14:42 ` Barry Margolin
[not found] ` <<barmar-2BC802.10421910072015@88-209-239-213.giganet.hu>
2015-07-10 14:53 ` Drew Adams
[not found] ` <<barmar-500871.19271109072015@88-209-239-213.giganet.hu>
2015-07-10 0:33 ` Drew Adams
[not found] ` <mailman.6590.1436397914.904.help-gnu-emacs@gnu.org>
2015-07-09 14:01 ` Barry Margolin
2015-07-09 14:10 ` Rusi
2015-07-09 22:27 ` Emanuel Berg
[not found] ` <mailman.6639.1436481016.904.help-gnu-emacs@gnu.org>
2015-07-10 3:10 ` Rusi
2015-07-10 16:00 ` Emanuel Berg
2015-07-09 22:19 ` Emanuel Berg
[not found] ` <<barmar-F23189.10014209072015@88-209-239-213.giganet.hu>
2015-07-09 15:33 ` Drew Adams
2015-07-12 1:47 ` Emanuel Berg
2015-07-12 16:59 ` Drew Adams
2015-07-13 0:46 ` Emanuel Berg
2015-07-13 7:26 ` Yuri Khan
2015-07-13 23:47 ` Emanuel Berg
2015-07-14 6:23 ` Yuri Khan
2015-07-14 21:58 ` Emanuel Berg
2015-07-19 0:59 ` Robert Thorpe
2015-07-28 0:24 ` Emanuel Berg
2015-07-30 1:40 ` Robert Thorpe
[not found] ` <mailman.7638.1438220428.904.help-gnu-emacs@gnu.org>
2015-07-30 2:49 ` Rusi
2015-07-30 2:53 ` Rusi
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