From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Pascal J. Bourguignon" Newsgroups: gmane.emacs.help Subject: Re: never use `eval' Date: Fri, 17 Jul 2015 10:55:32 +0200 Organization: Informatimago Message-ID: <87vbdjjh8b.fsf@kuiper.lan.informatimago.com> References: <87io9lmb4z.fsf@mbork.pl> <87oajdkqc7.fsf@kuiper.lan.informatimago.com> <87zj2w29ch.fsf@nl106-137-147.student.uu.se> <87d1zrlfz6.fsf@kuiper.lan.informatimago.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: ger.gmane.org 1437123620 3602 80.91.229.3 (17 Jul 2015 09:00:20 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 17 Jul 2015 09:00:20 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Fri Jul 17 11:00:17 2015 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 1ZG1VB-0002mB-9K for geh-help-gnu-emacs@m.gmane.org; Fri, 17 Jul 2015 11:00:17 +0200 Original-Received: from localhost ([::1]:43608 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZG1VA-0001TL-PA for geh-help-gnu-emacs@m.gmane.org; Fri, 17 Jul 2015 05:00:16 -0400 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 43 Original-X-Trace: individual.net UiChvE6IggWfKHvICdWStQXqD+A9MlxSb/whlxMHycc6w9RyHq Cancel-Lock: sha1:MWY4NzVlNzcxMTM1ZDAxM2YwZDA3ZTc3NzcyYTFjNjdlNzhiZjAzMA== sha1:nrEsu1MM4dX9NvdGSFHOKnCJ6cM= Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg== X-Accept-Language: fr, es, en User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) Original-Xref: usenet.stanford.edu gnu.emacs.help:213493 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:105779 Archived-At: Barry Margolin writes: > In article <87d1zrlfz6.fsf@kuiper.lan.informatimago.com>, > "Pascal J. Bourguignon" wrote: >> Doesn't seem to work: >> >> (setf lexical-binding t) >> >> (let ((x 42)) >> (eval 'x t)) >> Debugger entered--Lisp error: (void-variable x) >> >> (let ((x 42)) >> (eval 'x nil)) >> Debugger entered--Lisp error: (void-variable x) > > I don't think that could be expected to work. Since eval is a function, > not a special form, there's no way it can access the lexical environment > outside it. I assume the LEXICAL parameter means that it implements > lexical binding in the code being evaluated, e.g. if you do: > > (eval '(let ((x 42)) x) t) > > it binds x lexically, not dynamically. > > But it also says that LEXICAL can be an alist, so you could do: > > (eval 'x '((x . 42))) > > and it should return 42. Oh! I see… This is nice, to be able to pass an environment like this, because we could write macros that would build a "lexical environment" to be passed to eval… -- __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