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: why are there [v e c t o r s] in Lisp? Date: Sat, 17 Oct 2015 03:55:15 +0200 Organization: Informatimago Message-ID: <87twpqcl8c.fsf@kuiper.lan.informatimago.com> References: <87mvvjeg29.fsf@kuiper.lan.informatimago.com> <87io67pmr7.fsf@debian.uxu> <87mvvjzgup.fsf@fastmail.com> <87d1wfplu5.fsf@debian.uxu> <87io67zfl0.fsf@fastmail.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: ger.gmane.org 1445047245 27393 80.91.229.3 (17 Oct 2015 02:00:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 17 Oct 2015 02:00:45 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Sat Oct 17 04:00:44 2015 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 1ZnGna-00055A-Nu for geh-help-gnu-emacs@m.gmane.org; Sat, 17 Oct 2015 04:00:42 +0200 Original-Received: from localhost ([::1]:56620 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZnGna-0006L8-3z for geh-help-gnu-emacs@m.gmane.org; Fri, 16 Oct 2015 22:00:42 -0400 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 75 Original-X-Trace: individual.net pFL/rIqIEL4+9rFC3cNfCQl9QMF0vKwXUwdDP+Pwrz5/z0QXIw Cancel-Lock: sha1:NDBhODY0YTZjZDFjOTA1YjVmZmQ1ODhkZWQzODliMjEyODAxZTdkOQ== sha1:xmDDV9W1HYcyrSVIF0/VMyy5VtU= 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/24.3 (gnu/linux) Original-Xref: usenet.stanford.edu gnu.emacs.help:215402 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:107686 Archived-At: Emanuel Berg writes: > Random832 writes: > >> The thing is, if you can car a string people will >> wonder why you can't cdr it. And with mutable >> objects it's hard to make cdr work right. (fsvo >> "right") > > You can't `car' a string or do anything with it that > requires it to be a list, because it isn't. If you try > to car it, the string will fail the `listp' test. > But because it is natural to think of strings as lists > of chars, perhaps from the C days of, say > > char *str = malloc(strlen(argv[argc - 1])); > > or actually because it is normal for humans to think > of strings that way, it should be pointed out - and > now that has happened - that the "string" syntax isn't > a shorthand for creating lists of chars. In emacs lisp it'd be difficult to do it, but in Common Lisp it's trivial: (defpackage "EB-LISP" (:use "COMMON-LISP") (:shadow "CAR" "CDR" "CONSP" "LISTP") (:export . #.(let ((syms '())) (do-external-symbols (s "COMMON-LISP" syms) (push (symbol-name s) syms))))) (in-package "EB-LISP") (defun car (x) (if (vectorp x) (aref x 0) (cl:car x))) (defun cdr (x) (if (vectorp x) (if (< 1 (length x)) (make-array (1- (length x)) :element-type (array-element-type x) :displaced-to x :displaced-index-offset 1) '()) (cl:cdr x))) (defun consp (x) (or (vectorp x) (cl:consp x))) (defun listp (x) (or (vectorp x) (cl:listp x))) (defpackage "EB-LISP-USER" (:use "EB-LISP")) (in-package "EB-LISP-USER") (loop :for string := "hello world" :then (cdr string) :while string :collect (car string)) ;; --> (#\h #\e #\l #\l #\o #\ #\w #\o #\r #\l #\d) Instead, in emacs-lisp you can prefix your symbols: eb-lisp-car eb-lisp-cdr etc… (and you have to implement more things yourself, since there are no displaced arrays, etc). -- __Pascal Bourguignon__ http://www.informatimago.com/ “The factory of the future will have only two employees, a man and a dog. The man will be there to feed the dog. The dog will be there to keep the man from touching the equipment.” -- Carl Bass CEO Autodesk