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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]
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