Question on Positive[x]=True
- To: mathgroup at smc.vnet.net
- Subject: [mg7791] Question on Positive[x]=True
- From: Raya Firsov-Khanin <raya at mech.ed.ac.uk>
- Date: Tue, 8 Jul 1997 22:41:06 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Dear Steve,
I have the following question. I want to state that a variable
x is positive. On page 1170 of the Third edition of The Mathematica book
it is said that I can do it by making a definition
Positive[x] = True
However, while trying to do it I get a message :
Set::write: Tag Positive in Positive[x] is Protected
Any suggestions on how one can make variables positive, negative etc?
Thanks a lot.
Raya Khanin.
University of Edinburgh