From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Marcin Borkowski Newsgroups: gmane.emacs.help Subject: Re: no empty (zero) string predicate in Elisp Date: Sun, 26 Apr 2015 22:11:50 +0200 Message-ID: <87lhhebqex.fsf@mbork.pl> References: <87h9s4rhx5.fsf@debian.uxu> <87wq0zkqxa.fsf@debian.uxu> <87oambhqze.fsf@kuiper.lan.informatimago.com> <87a8xu20ys.fsf@debian.uxu> <87tww2zp3f.fsf@debian.uxu> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1430079163 30206 80.91.229.3 (26 Apr 2015 20:12:43 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 26 Apr 2015 20:12:43 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Sun Apr 26 22:12:37 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 1YmSum-00046q-1u for geh-help-gnu-emacs@m.gmane.org; Sun, 26 Apr 2015 22:12:32 +0200 Original-Received: from localhost ([::1]:52006 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YmSul-0002uS-1P for geh-help-gnu-emacs@m.gmane.org; Sun, 26 Apr 2015 16:12:31 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:42803) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YmSua-0002rw-Nc for help-gnu-emacs@gnu.org; Sun, 26 Apr 2015 16:12:21 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YmSuW-0003m4-Mz for help-gnu-emacs@gnu.org; Sun, 26 Apr 2015 16:12:20 -0400 Original-Received: from mail.mojserwer.eu ([2a01:5e00:2:52::8]:60553) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YmSuW-0003lx-GE for help-gnu-emacs@gnu.org; Sun, 26 Apr 2015 16:12:16 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by mail.mojserwer.eu (Postfix) with ESMTP id DFBCF4F607B for ; Sun, 26 Apr 2015 22:12:14 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.mojserwer.eu Original-Received: from mail.mojserwer.eu ([127.0.0.1]) by localhost (mail.mojserwer.eu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id YDlccYRWogcE for ; Sun, 26 Apr 2015 22:11:57 +0200 (CEST) Original-Received: from localhost (unknown [109.232.24.146]) by mail.mojserwer.eu (Postfix) with ESMTPSA id D2AE04F6079 for ; Sun, 26 Apr 2015 22:11:56 +0200 (CEST) In-reply-to: <87tww2zp3f.fsf@debian.uxu> X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2a01:5e00:2:52::8 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:104012 Archived-At: On 2015-04-26, at 21:06, Emanuel Berg wrote: > Marcin Borkowski writes: > >>> "Predicate" is a word from the grammars of human >>> languages, but I don't know its exact meaning, >>> neither there or in programming languages (until >>> now as for programming). >> >> AFAIK, "predicate" is a word from /logic/, and it >> means (more or less) a function which consumes one >> or more arguments of any type and gives back >> a truth-value. > > Doesn't all functions in logic do that? First of all: IANAL (here L = logician;-)). But... For starters, in propositional calculus (AFAIK, also in first-order logic) there are no "functions" per se, since there are no /sets/. Furthermore, in the logic systems usually used by us mathematicians there are no /types/. AFAIK, the analogue of "type mismatch" in these systems is just a plain old "syntax error". What you probably refer to is the fact that in these simple logic systems both predicates and logical connectives "generate" truth-values. However, there are other possibilities; analogues of "functions" in these systems are called "terms". Best, -- Marcin Borkowski http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski Faculty of Mathematics and Computer Science Adam Mickiewicz University