From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.help Subject: Re: let-bind a varlist only known at run time Date: Mon, 05 Jun 2017 04:49:47 +0200 Message-ID: <87efuzup10.fsf@drachen> References: <28921.59572.342625.22836@gargle.gargle.HOWL> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1496631020 788 195.159.176.226 (5 Jun 2017 02:50:20 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 5 Jun 2017 02:50:20 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) Cc: help-gnu-emacs@gnu.org To: Roland Winkler Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Mon Jun 05 04:50:17 2017 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dHi5w-0008O7-SX for geh-help-gnu-emacs@m.gmane.org; Mon, 05 Jun 2017 04:50:16 +0200 Original-Received: from localhost ([::1]:59323 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dHi62-0001aS-8W for geh-help-gnu-emacs@m.gmane.org; Sun, 04 Jun 2017 22:50:22 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:48564) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dHi5d-0001aL-Ta for help-gnu-emacs@gnu.org; Sun, 04 Jun 2017 22:49:58 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dHi5d-00081r-81 for help-gnu-emacs@gnu.org; Sun, 04 Jun 2017 22:49:57 -0400 Original-Received: from mout.web.de ([217.72.192.78]:64610) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dHi5Y-0007xl-S8; Sun, 04 Jun 2017 22:49:53 -0400 Original-Received: from drachen.dragon ([94.218.223.218]) by smtp.web.de (mrweb102 [213.165.67.124]) with ESMTPSA (Nemesis) id 0M7srs-1e3uvc0Sky-00vOwx; Mon, 05 Jun 2017 04:49:48 +0200 In-Reply-To: <28921.59572.342625.22836@gargle.gargle.HOWL> (Roland Winkler's message of "Sun, 4 Jun 2017 15:43:37 -0500") X-Provags-ID: V03:K0:FFQiRDiSv8VENhW69A+JzGNKnkBSJQjXDdsQgo8Qx7GxvZfuXCQ rclgtdN0Nbkj3C4Ewz5coueyJFKuEjkklJ2BY7++s7loOkFgaCJP0yFc/amnYOcrdSAzVAO yIj2+pU1CiS13zzouGQUGM3xIM7d0lspp6f+tMgR0d1IygBR1TyHkQLEVbXOCMnzUgfN0+j zBnKijkXve4OT53wbgh3Q== X-UI-Out-Filterresults: notjunk:1;V01:K0:JjVH73GRc3A=:TRCqEBQpKAqTVnuFUNiPuV /y+8S0p4pprtu8NjTUBDNJJIMv0CESCKRfirfgmHN26iPKDkKTy9bOknhoNoXm/l61reByj5X z/4nerW3kwceR+UWGHFmnE1K7n7rSL6q1leLP4EArgL2lIW+0HtnMjVT9ItVaMNVtJhqS6tlj x1YtaXYrRcvCQTUd2lx8uS215DeEx21ebg6aRZb8mtcV8ben9A+dWku6NY01ewrbr9KAkDvw4 ZjMryyFQjHobZ2oWCa2tflBEziq0Ws0eTo8+d7vfM2THy18Y/Qbq7UZFweNxlElqjQXscV+12 WG6ISP1aliyhRKshQ11uM0aDV4yfnXdv9buBsz2Xf+8MdVcKMGLgEZ9CjkHpQ9MPeY37v/Pph Bb1VxG4SHvjzPxe6rlxf4PhxtSt14mucsR1CKrMfMpCkUot1z1Om2rPaSNC6CO+iaKq4V1Y0J DggrmsKFQPr4Ldxqg5Sib0C5h3yw91tqHWldw3LIJzDobabfccNQHzKDfeSZduzQ4Zna3u/77 L8bBm7JUljEodwdEM2qy5p4R1n8aa1ZU9V0ja/dsqtFzzIYYXJa8wgVhAW2foJEEDGMLLWD0B Ho/rYJO8QdcGzuL2wnWblIRkgE2cRBTyib4Lex1Oq17fzMoOA/N77IPj1l1C9We0cZyBlj0nA 5Q0nx1z89J6gmq86sHjBUFwBsN6uhpfChsSP/1TwLjYo7qkzl1umJ++EB+tRdsXIDePZ8EHEz Hn72aLAofs93enXWto/M1mlUd93XY8EqDFXBZrlUv3yGdRmpcUZB5xYVRzaiCI0961xyvbdI X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 217.72.192.78 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.21 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" Xref: news.gmane.org gmane.emacs.help:113356 Archived-At: "Roland Winkler" writes: > Normally the varlist for the special let form is hardcoded. Is it > possible to specify the varlist only at runtime? `cl-progv'? > On the other hand, I expect that efficiency is not an issue for the > body appearing in let. So if there is nothing else I could construct > the complete let-form at runtime and pass it on to `eval'. FWIW that's what `cl-progv' is doing, more or less. The body is pasted into a lambda constructed before calling eval so that it can be compiled. The resulting semantics can be a bit surprising, though; for example (let ((x 0)) (cl-progv (list 'x) (list 1) (funcall (lambda () x)))) yields 0 with lexical-binding on, and (cl-progv (list 'x) (list 1) (funcall (lambda () x))) yields 1. Michael.