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: Mon, 04 Mar 2013 20:15:51 +0100 Organization: Informatimago Message-ID: <87boazvuvs.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 1362425685 8164 80.91.229.3 (4 Mar 2013 19:34:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 4 Mar 2013 19:34:45 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Mon Mar 04 20:35:06 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 1UCbA9-0006VK-Gb for geh-help-gnu-emacs@m.gmane.org; Mon, 04 Mar 2013 20:35:05 +0100 Original-Received: from localhost ([::1]:60565 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UCb9o-0003Xo-1J for geh-help-gnu-emacs@m.gmane.org; Mon, 04 Mar 2013 14:34:44 -0500 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 40 Original-X-Trace: individual.net yHKVtdokJYTdzQTXqsDrzguab7e5k4SgW7Cd8XnNr/SsKWSXFOsHmIqMKtOS8DzAXF Cancel-Lock: sha1:YTUyMDU2NzE0OGRmODE2MmYyODFiOTVkMThiM2Y0ZjgyYThhMjg2Yg== sha1:b1UVBFx/R/mQNHlWvlVNnTwuEPI= 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:197066 X-Mailman-Approved-At: Mon, 04 Mar 2013 14:34:19 -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:89346 Archived-At: 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. If the value bound to yank-undo-function is not nil, then it's returned, else the symbol delete-region is returned (since it's not nil). (or a b) <=> (let ((first-arg a)) (if first-arg first-arg b)) The temporary variable is needed for (let ((i 0)) (or (incf i) 42)) returns 1, not 2. (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))) -- __Pascal Bourguignon__ http://www.informatimago.com/ A bad day in () is better than a good day in {}.