From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.science.mathematics.categories/6663 Path: news.gmane.org!not-for-mail From: Clemson Steve Newsgroups: gmane.science.mathematics.categories Subject: Re: Explanations Date: Mon, 02 May 2011 13:01:10 -0400 Message-ID: References: Reply-To: Clemson Steve NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: dough.gmane.org 1304384121 5017 80.91.229.12 (3 May 2011 00:55:21 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Tue, 3 May 2011 00:55:21 +0000 (UTC) Cc: peasthope@shaw.ca, catbb To: Charles Wells Original-X-From: majordomo@mlist.mta.ca Tue May 03 02:55:16 2011 Return-path: Envelope-to: gsmc-categories@m.gmane.org Original-Received: from smtpx.mta.ca ([138.73.1.4]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1QH3tT-000410-Vq for gsmc-categories@m.gmane.org; Tue, 03 May 2011 02:55:16 +0200 Original-Received: from mlist.mta.ca ([138.73.1.63]:54299) by smtpx.mta.ca with esmtp (Exim 4.71) (envelope-from ) id 1QH3r5-00059i-3l; Mon, 02 May 2011 21:52:47 -0300 Original-Received: from majordomo by mlist.mta.ca with local (Exim 4.71) (envelope-from ) id 1QH3r2-0006Ol-7R for categories-list@mlist.mta.ca; Mon, 02 May 2011 21:52:44 -0300 In-Reply-To: Precedence: bulk Xref: news.gmane.org gmane.science.mathematics.categories:6663 Archived-At: I think this is a perfect example of when something is or is not an explanation. It's both in this case: to the cogniscenti, it is perfectly clear; the novice is going to head off on the wrong track. On 4/30/11 15:58, Charles Wells wrote: > In the expression "any x:T->X" the T depends on x. If you use the > arrow notation you seem bound to name the domain of the morphism. You > could say "for any x with codomain X there is an e:dom x -> X ..." but > in the rest of the sentence you will have to mention the domain again. > > My impression is that notation "any x:T->X" where T depends on x > without that fact being mentioned is common in category theory > writing. There is nothing wrong with this if a reader understands the > intent. -- Dr. D. E. Stevenson Associate Professor Director, Insitute for Modeling and Simulation Applications School of Computing, Clemson University [For admin and other information see: http://www.mta.ca/~cat-dist/ ]