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Positive[a] = True ???

• To: mathgroup at smc.vnet.net
• Subject: [mg2518] Positive[a] = True ???
• From: domokos at chaph.usc.edu (Marius)
• Date: Wed, 15 Nov 1995 02:02:14 -0500
• Organization: University of Southern California, Los Angeles, CA

I assume that this topic has been addressed already, and I think I actually
remember reading something about it before. However, I have not been able
to find anything in the archive.

Anyway, here is my problem:

The book says that it is possible to declare a variable as beeing positive
without assigning any numerical value to it. However, when I try it in version
2.2.2 on a PowerMac, Mathematica rejects the assignment with a message
regarding the tag protection.

For example:

IN>> Positive[a] = True;
OUT>> Set::write: Tag Positive in Positive[a] is Protected.

What is the problem?

Thank you.

Frank Domokos