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: About `funcall' Date: Tue, 05 Mar 2013 00:23:08 +0100 Organization: Informatimago Message-ID: <87y5e2vjfn.fsf@kuiper.lan.informatimago.com> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1362441816 30744 80.91.229.3 (5 Mar 2013 00:03:36 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 5 Mar 2013 00:03:36 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Tue Mar 05 01:03:58 2013 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 1UCfMK-0003HX-VR for geh-help-gnu-emacs@m.gmane.org; Tue, 05 Mar 2013 01:03:57 +0100 Original-Received: from localhost ([::1]:44754 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UCfLz-0002oa-G6 for geh-help-gnu-emacs@m.gmane.org; Mon, 04 Mar 2013 19:03:35 -0500 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 39 Original-X-Trace: individual.net ZM+tXnELEDNEM9tR3nHp6wAPQiUoSH/pJ+LmIZxPb7P9z/RNWV6W2kEUrIrYhnsNtR Cancel-Lock: sha1:MjUyYTI3YTllZjY3NTZjOWU2NGIzZTU5YzZiOTMyNDQxYzc2NmI3Nw== sha1:w3ijdj/K21KZXhDmlv7mZ8BOrp8= 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/24.2 (gnu/linux) Original-Xref: usenet.stanford.edu gnu.emacs.help:197073 X-Mailman-Approved-At: Mon, 04 Mar 2013 19:03:22 -0500 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:89353 Archived-At: Xue Fuqiao writes: >> Xue Fuqiao writes: >> >>> In `yank-pop', there is an sexp about `funcall': >>> >>> (funcall (or yank-undo-function 'delete-region) (point) (mark t)) >>> >>> IIRC the first argument for `funcall' should be a function, so I'm >>> confused with this usage. Can somebody explain it to me? Thanks. >> >> `or' returns the first argument that is not nil, or nil when all the >> arguments are nil. > > I see, thanks. > >> (defmacro .or (&rest args) >> (if (null args) >> 'nil >> (let ((var (gensym))) >> `(let ((,var ,(first args))) >> (if ,var >> ,var >> (.or ,@(rest args))))))) >> >> (macroexpand '(.or a b)) >> --> (let ((#1=#:G90861 a)) (if #1# #1# (\.or b)))-- > > What does "(first args)" mean here? Does it mean "(car args)"? Yes. And (rest args) is the same as (cdr args). But since I consider here args to be a list, and not a cons cell, then I use first and rest. I use car and cdr only when I consider cons cells. -- __Pascal Bourguignon__ http://www.informatimago.com/ A bad day in () is better than a good day in {}.