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MathGroup Archive 1997

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Re: Question on Positive[x]=True

  • To: mathgroup at
  • Subject: [mg7824] Re: Question on Positive[x]=True
  • From: Tony.Nicolas at (Tony NICOLAS)
  • Date: Mon, 14 Jul 1997 03:01:08 -0400
  • Organization: INSA-LMR
  • Sender: owner-wri-mathgroup at

In article <5pv0ob$id3 at>, Raya Firsov-Khanin
<raya at> 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

If you want take a test you must write Positive[x] == True

Attention : == and not =

Tony Nicolas
             INSA Rouen

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