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

*To*: mathgroup at smc.vnet.net*Subject*: [mg66701] Re: Interval[{a,b}]-Interval[{a,b}] = 0?*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Sat, 27 May 2006 03:52:40 -0400 (EDT)*Organization*: The University of Western Australia*References*: <e510r2$8eg$1@smc.vnet.net> <e514do$96v$1@smc.vnet.net> <200605250658.CAA03721@smc.vnet.net> <e56duk$1sn$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <e56duk$1sn$1 at smc.vnet.net>, Andrzej Kozlowski <akoz at mimuw.edu.pl> wrote: > Note that in Mathematica you will get things like: > > In[8]:= > "a dog" - "a dog" > > Out[8]= > 0 > > Now, one could also argue that this is a bug, since first of all > subtraction of strings (or animals) is not defined and besides there > is no reason to assume that the second dog is the same as the first > one. Unfortunately Mathematica is very simple minded and when it has > no rules for dealing with some object you can always subtract it from > itself and get 0 so this fact alone gives you potentially an infinite > number of bugs to could complain about! > In addition, in Lewis Carroll's "Through The Looking Glass" the > question of subtracting a bone from a dog is discussed and a > definitive answer provided. I am afraid this answer is also > unimplemented in Mathematica, so from this point of view there is > another bug, which might result in seriously wrong answers in > computations involving dogs and bones. I would argue that there has never been a better posting on MathGroup! Keep up the good work Andrzej. But this made me think of the line "give her dog a bone" in "Cool for Cats" by UK Squeeze -- probably inappropriate for this newsgroup. Cheers, Paul _______________________________________________________________________ Paul Abbott Phone: 61 8 6488 2734 School of Physics, M013 Fax: +61 8 6488 1014 The University of Western Australia (CRICOS Provider No 00126G) AUSTRALIA http://physics.uwa.edu.au/~paul

**References**:**Re: Interval[{a,b}]-Interval[{a,b}] = 0?***From:*"Richard Fateman" <fateman@cs.berkeley.edu>