Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!snorkelwacker!think!linus!wdh
From: wdh@linus.UUCP (W. Dale Hall)
Newsgroups: comp.theory
Subject: Re: Answers... (was Re: Program correctness etc.)
Summary: A nit. Picked before your very eyes.
Keywords: metric, real line
Message-ID: <94701@linus.UUCP>
Date: 7 Feb 90 22:07:28 GMT
References: <643@shodha.dec.com> <19630@netnews.upenn.edu> <1280@oravax.UUCP> <10661@saturn.ADS.COM> <KERS.90Jan29091233@cdollin.hpl.hp.com> <1990Jan29.163009.14547@cs.rochester.edu>
Reply-To: wdh@linus.UUCP (W. Dale Hall)
Followup-To: comp.theory
Distribution: na
Organization: The MITRE Corporation, Bedford MA
Lines: 19

In article <1990Jan29.163009.14547@cs.rochester.edu>
                      fulk@cs.rochester.edu (Mark Fulk) writes: 
>
>2) d(x,y) >= 0; d(x,x) = 0; d(x,z) >= d(x,y) + d(y,z).
>	Applies to lots of spaces, e.g. the real line.
>
I'm having trouble with this one. To me, it certainly seems that

 	d(4,5) < d(4,-1000) + d(-1000,5)

That's the only example I could come up with, but it seems to be
sufficient to disprove the inequality
 
	d(x,z) >= d(x,y) + d(y,z) 

given above. 

That's all I know for now.
						Dale.