From: "Pascal J. Bourguignon" <pjb@informatimago.com>
To: help-gnu-emacs@gnu.org
Subject: Re: What does "lacks a prefix" mean?
Date: Fri, 10 Jul 2015 02:49:25 +0200 [thread overview]
Message-ID: <87a8v4q1ka.fsf@kuiper.lan.informatimago.com> (raw)
In-Reply-To: mailman.6643.1436488423.904.help-gnu-emacs@gnu.org
Drew Adams <drew.adams@oracle.com> writes:
>> > And non-parallelizable theoretically :)
>>
>> Regular let isn't parallelizable. It specifies that the value
>> expressions are evaluated in order.
>>
>> The only difference between the two is the environment within which
>> later expressions are evaluated.
>
> FWIW, Common Lisp specifies that "let performs the bindings
> in parallel and let* does them sequentially."
>
> That is theoretical, just a restatement that `let' bindings
> are independent. But it means that yes, they *could* be
> evaluated in parallel (because they are independent).
IF they are independent, and notably IF they are side effect free.
(let ((i 0))
(cons (let ((i 42)
(a (print (incf i)))
(b (print (incf i)))
(c (print (incf i))))
(list i a b c))
i))
prints:
1
2
3
--> ((42 1 2 3) . 3)
Here, there's now way the initialization expressions in the inner let
be evaluated in parallel. The left-to-right evaluation order is
imperative, because of the side effects.
--
__Pascal Bourguignon__ http://www.informatimago.com/
“The factory of the future will have only two employees, a man and a
dog. The man will be there to feed the dog. The dog will be there to
keep the man from touching the equipment.” -- Carl Bass CEO Autodesk
next prev parent reply other threads:[~2015-07-10 0:49 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
[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 [this message]
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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