From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.help Subject: Re: Two questions about generalized variables Date: Sun, 21 Feb 2016 14:34:05 +0100 Message-ID: <877fhydw6q.fsf@web.de> References: <87ziuu4p8k.fsf@ericabrahamsen.net> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1456061699 10699 80.91.229.3 (21 Feb 2016 13:34:59 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 21 Feb 2016 13:34:59 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Sun Feb 21 14:34:50 2016 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 1aXU9v-000336-Ei for geh-help-gnu-emacs@m.gmane.org; Sun, 21 Feb 2016 14:34:47 +0100 Original-Received: from localhost ([::1]:41126 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aXU9r-0006qG-Bt for geh-help-gnu-emacs@m.gmane.org; Sun, 21 Feb 2016 08:34:43 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:39842) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aXU9f-0006mo-Fb for help-gnu-emacs@gnu.org; Sun, 21 Feb 2016 08:34:32 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aXU9a-00066e-Ge for help-gnu-emacs@gnu.org; Sun, 21 Feb 2016 08:34:31 -0500 Original-Received: from plane.gmane.org ([80.91.229.3]:34063) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aXU9a-00066a-A3 for help-gnu-emacs@gnu.org; Sun, 21 Feb 2016 08:34:26 -0500 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1aXU9W-0002ex-VE for help-gnu-emacs@gnu.org; Sun, 21 Feb 2016 14:34:23 +0100 Original-Received: from dslb-092-074-189-190.092.074.pools.vodafone-ip.de ([92.74.189.190]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sun, 21 Feb 2016 14:34:22 +0100 Original-Received: from michael_heerdegen by dslb-092-074-189-190.092.074.pools.vodafone-ip.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sun, 21 Feb 2016 14:34:22 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 40 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: dslb-092-074-189-190.092.074.pools.vodafone-ip.de User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.91 (gnu/linux) Cancel-Lock: sha1:B90DS7dbeqfcr8bpku80XcWbjQI= 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:109244 Archived-At: Eric Abrahamsen writes: > It looks like plist-get doesn't return a setf-able place. But `symbol-plist' has a gv-expander and refers to an alist. `alist-get' has a gv-expander, too. So i think you would end up with something like (setf (alist-get key (symbol-plist 'symbol)) value) I think. > The second question is setting hashtable entries. Right now I have code > like this: > > (setf (gethash uuid my-hashtable) > (append (list (list 'thingone 'thingtwo)) > (gethash uuid my-hashtable))) Isn't that more or less `push'? > I assume this is no more or less efficient than let-ting the gethash, > manipulating the value, then using puthash to put it back in. Now I've > written this: > [corrected version from the second message] > (cl-symbol-macrolet ((entry (gethash uuid my-hashtable))) > (setf entry (append (list (list 'thingone 'thingtwo)) > entry))) > > This is a simplistic example, but -- is this actually going to be any > faster or more efficient than the first version? Does it only access > the hashtable once? `push' with `gethash' and the above code expand more or less to the same. And I think this must access the hash-table twice: once `gethash', and once `puthash'. Michael.