Re: Question on Positive[x]=True
- To: mathgroup at smc.vnet.net
- Subject: [mg7827] Re: [mg7791] Question on Positive[x]=True
- From: seanross at worldnet.att.net
- Date: Mon, 14 Jul 1997 03:01:10 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Raya Firsov-Khanin wrote: > > 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 Protected is an attribute which must be removed before modifying. Try Unprotect[Positive]; Positive[x]=True; Protect[Positive];