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MathGroup Archive 2004

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Assuming/Block doesn't invoke $Post ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg45522] Assuming/Block doesn't invoke $Post ?
  • From: "Drago Ganic" <drago.ganic at in2.hr>
  • Date: Mon, 12 Jan 2004 02:15:33 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

I thought that I could use something like this to assert that all variables
are real and not complex:
  {$Post , $Assumptions} = {Refine, _Symbol \[Element] Reals};

It seems to work with:
  Sqrt[x^2]]
  Abs[x]

and

  Refine[Sqrt[x^2], x > 0]
  x

But I would like not to use Refine to make additional assumptions. Instead I
would like to use Assuming:

  Assuming[x > 0, Sqrt[x^2]]
  Abs[x]

Why doesn't Assuming  (or the Block equivalent)  apply Refine automatically
?!?!

Greetings from Croatia,
drago



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