From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.help Subject: Re: Always using let* Date: Mon, 15 Sep 2014 08:31:35 -0400 Message-ID: References: <87fvfukmso.fsf@Equus.decebal.nl> <87mwa1lhb1.fsf@kuiper.lan.informatimago.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1410784350 10252 80.91.229.3 (15 Sep 2014 12:32:30 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 15 Sep 2014 12:32:30 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Mon Sep 15 14:32:23 2014 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XTVS9-0004V6-CO for geh-help-gnu-emacs@m.gmane.org; Mon, 15 Sep 2014 14:32:21 +0200 Original-Received: from localhost ([::1]:59459 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTVS9-0008Db-13 for geh-help-gnu-emacs@m.gmane.org; Mon, 15 Sep 2014 08:32:21 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:45043) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTVRo-0008DC-4e for help-gnu-emacs@gnu.org; Mon, 15 Sep 2014 08:32:07 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XTVRg-0000C5-0d for help-gnu-emacs@gnu.org; Mon, 15 Sep 2014 08:32:00 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:45672) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTVRf-0000Bq-QZ for help-gnu-emacs@gnu.org; Mon, 15 Sep 2014 08:31:51 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1XTVRd-0004HO-Nx for help-gnu-emacs@gnu.org; Mon, 15 Sep 2014 14:31:49 +0200 Original-Received: from 69-165-145-6.dsl.teksavvy.com ([69.165.145.6]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Sep 2014 14:31:49 +0200 Original-Received: from monnier by 69-165-145-6.dsl.teksavvy.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Sep 2014 14:31:49 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 18 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: 69-165-145-6.dsl.teksavvy.com User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) Cancel-Lock: sha1:KnJDuX2fcO6pM5sQm6ZwhNtiKOI= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:99918 Archived-At: > But if you have side-effect free expressions, (or at least, provably > independent ones), then they could be evaluated in parallel despite the > left-to-right rule. Same holds for let* or pretty much anything else for that matter: if some analysis can prove that it can be done in parallel, well, then unsurprisingly it can be performed in parallel. But it's not the "parallel binding" semantics of `let' that lets you do that. While some details of language semantics can make analysis of code easier for that (e.g. the non-aliasing constraints on arguments in Fortran), I've never heard of anyone being able to use the parallel-binding of "let" for that. So, I stand by my claim: it's an Urban Legend. Stefan