From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Drew Adams" Newsgroups: gmane.emacs.help Subject: RE: Prefix-Arg (non-interactive!) in Info Date: Fri, 13 Aug 2010 13:33:24 -0700 Message-ID: <785218C66A0048DBB2DE688D28131E06@us.oracle.com> References: <878w4avcir.fsf@mean.albasani.net> <838w4av8xg.fsf@gnu.org><87r5i2ttle.fsf@mean.albasani.net> <837hjuv6jn.fsf@gnu.org><4F47505C2BAA45CC9C8AFE61D9F16B2A@us.oracle.com> <874oeytlmx.fsf@mean.albasani.net> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Trace: dough.gmane.org 1281731678 17518 80.91.229.12 (13 Aug 2010 20:34:38 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Fri, 13 Aug 2010 20:34:38 +0000 (UTC) Cc: help-gnu-emacs@gnu.org To: "'Memnon Anon'" Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Fri Aug 13 22:34:37 2010 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Ok0xV-0003fj-Im for geh-help-gnu-emacs@m.gmane.org; Fri, 13 Aug 2010 22:34:33 +0200 Original-Received: from localhost ([127.0.0.1]:60437 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Ok0xV-0006Zh-29 for geh-help-gnu-emacs@m.gmane.org; Fri, 13 Aug 2010 16:34:33 -0400 Original-Received: from [140.186.70.92] (port=34087 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Ok0wz-0006YM-7D for help-gnu-emacs@gnu.org; Fri, 13 Aug 2010 16:34:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1Ok0wt-00084C-NT for help-gnu-emacs@gnu.org; Fri, 13 Aug 2010 16:34:01 -0400 Original-Received: from rcsinet10.oracle.com ([148.87.113.121]:57139) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1Ok0wt-00083y-DR; Fri, 13 Aug 2010 16:33:55 -0400 Original-Received: from rcsinet15.oracle.com (rcsinet15.oracle.com [148.87.113.117]) by rcsinet10.oracle.com (Switch-3.4.2/Switch-3.4.2) with ESMTP id o7DKXqLA019553 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 13 Aug 2010 20:33:54 GMT Original-Received: from acsmt353.oracle.com (acsmt353.oracle.com [141.146.40.153]) by rcsinet15.oracle.com (Switch-3.4.2/Switch-3.4.1) with ESMTP id o7DKXqGA011007; Fri, 13 Aug 2010 20:33:52 GMT Original-Received: from abhmt021.oracle.com by acsmt353.oracle.com with ESMTP id 515661571281731607; Fri, 13 Aug 2010 13:33:27 -0700 Original-Received: from dradamslap1 (/10.159.218.59) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 13 Aug 2010 13:33:27 -0700 X-Mailer: Microsoft Office Outlook 11 In-Reply-To: <874oeytlmx.fsf@mean.albasani.net> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5931 Thread-Index: Acs7FnircvB3sXQrS3OSgBSUNZG6DgADxHAg X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:74627 Archived-At: > I remember seeing it when I searched, but I dismissed it too quickly. > Curious, an 'integer', or a 'list of one element' ... which is an > integer. > > Well, thats then the way it is. No, this is not just a curiosity. If you read a bit about nil, you will see that it can act in Lisp in two important ways: 1. It represents (it is) an empty list. 2. It represents false, with non-nil representing true. Instead of false and true, think alligator and non-alligator: _any_ dichotomous choice. The _raw_ prefix arg is most often looked at as a boolean choice: nil or non-nil, the particular non-nil value making no difference. But a non-nil value can be, well, anything other than nil. And that means that a program is free to attach different meanings (behaviors) to different non-nil values. In addition, a non-nil raw prefix argument, which can be one of several things (an integer, the atom `-', a cons with integer car, etc.) also has an associated numeric value, given by function `prefix-numeric-value'. A given function could, if it wanted, produce different behaviors for different numerical values of its prefix arg. Or, for a cons value, it could produce different behaviors depending on which integer is the car of its cons value (4, 16, 256,...). And it can mix these possibilities. The possibilities are endless (there are an endless number of integers, for one thing).