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

*To*: mathgroup at smc.vnet.net*Subject*: [mg66734] Re: [mg66691] Re: Interval[{a,b}]-Interval[{a,b}] = 0?*From*: "G. Raymond Brown" <gbrown at runbox.com>*Date*: Sat, 27 May 2006 21:04:17 -0400 (EDT)*References*: <200605270751.DAA02935@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Some shallow comments on this thread: 1. This has been a lot of fun! Thanks to all contributors. 2. I learned a little about interval arithmetic. That's good, although I will probably never use any of it. 3. I think that both Frege and Godel would approve of the decisions made by the Mathematica developers, and of the comments by Andrzej. (Frege would probably want to change the notation used.) -GRB- ----- Start Original Message ----- From: Andrzej Kozlowski To: mathgroup at smc.vnet.net Subject: [mg66734] [mg66691] Re: Interval[{a,b}]-Interval[{a,b}] = 0? > On 27 May 2006, at 07:27, David W. Cantrell wrote: > > > > Concerning the fact that Interval[{a,b}]-Interval[{a,b}]=0 in > > Mathematica, > > Andrzej Kozlowski 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 > >> > > > > No animal was obliterated in producing that example! We're obviously > > dealing merely with strings, not dogs. Use-mention distinction. > > > > Well, actually things are not as simple as that. For example, what we > call the number 1 is not actually a number but, depending on context, > a letter that represents it, a few pixels on the monitor, and so > on... I dare say, it would be possible to implement dogs as strings > in Mathematica just as one implements integers, circles, real numbers > etc... Philosophically there need not be any essential difference > between dog and numbers, cf. Quine "On What There Is." etc. > > ----- End Original Message -----

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