Re: Interval[{a,b}]-Interval[{a,b}] = 0?

*To*: mathgroup at smc.vnet.net*Subject*: [mg66637] Re: Interval[{a,b}]-Interval[{a,b}] = 0?*From*: "Richard Fateman" <fateman at cs.berkeley.edu>*Date*: Thu, 25 May 2006 02:58:01 -0400 (EDT)*References*: <e510r2$8eg$1@smc.vnet.net> <e514do$96v$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

I'm sorry I was not clear in my original note, since several people seem to think I was objecting to [-1,1] - [-1,1] simplifying to [-2,2]. This is universally agreed to be correct in the "reliable computing" community, for the reason given by Johan, and I certainly agree with it. What is likely to be a bug, in my view, is the treatment of Interval[{a,b}]-Interval[{a,b}] , and I was just wondering if anyone could defend simplifying it to 0 as a feature. The closest I got was a suggestion that "this is not the right tool". One correct answer might be to leave it alone. or maybe after ascertaining that a,b are real and a<=b , the interval [-2*a,2*b]. The answer 0 not only is wrong, but apparently leads to bugs in Limit computations, where Interval notation is used /abused. "Johan Grönqvist" <johan.gronqvist at gmail.com> wrote in message news:e514do$96v$1 at smc.vnet.net... .... snipped... explanation of [-1,1]-[-1,1]=[-2,2]

**Follow-Ups**:**Re: Re: Interval[{a,b}]-Interval[{a,b}] = 0?***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>