From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: [PATCH] Add new function to test whether a key is present in a hash table. Date: Thu, 15 Feb 2018 17:59:22 -0500 Message-ID: References: <20180215203406.64372-1-phst@google.com> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1518735556 2690 195.159.176.226 (15 Feb 2018 22:59:16 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 15 Feb 2018 22:59:16 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Feb 15 23:59:11 2018 Return-path: Envelope-to: ged-emacs-devel@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 1emSUc-0008BY-T5 for ged-emacs-devel@m.gmane.org; Thu, 15 Feb 2018 23:59:07 +0100 Original-Received: from localhost ([::1]:40677 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emSWZ-0002qd-Qf for ged-emacs-devel@m.gmane.org; Thu, 15 Feb 2018 18:01:07 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:42726) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emSVU-0002oQ-PJ for emacs-devel@gnu.org; Thu, 15 Feb 2018 18:00:01 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emSVP-0000Fg-OL for emacs-devel@gnu.org; Thu, 15 Feb 2018 18:00:00 -0500 Original-Received: from [195.159.176.226] (port=48128 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1emSVP-0000FI-Gg for emacs-devel@gnu.org; Thu, 15 Feb 2018 17:59:55 -0500 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1emST4-0002eU-U1 for emacs-devel@gnu.org; Thu, 15 Feb 2018 23:57:30 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 12 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:hvnknfSC5XkQBEwkeR53ORbq/8M= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 195.159.176.226 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:222786 Archived-At: > Such a function is useful because in Emacs Lisp, 'gethash' cannot > return whether the key is present as in Common Lisp, and using > 'gethash' alone to test for presence is nontrivial. We could also implement it in Elisp: (defun hash-table-contains-p (key table) (let ((x '(:hash-table-contains-p))) (not (eq x (gethash key table x))))) -- Stefan