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MathGroup Archive 1996

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Re: Fourier and 0 and N

  • To: mathgroup at smc.vnet.net
  • Subject: [mg4938] Re: Fourier and 0 and N
  • From: Robert Knapp <rknapp>
  • Date: Mon, 7 Oct 1996 02:02:10 -0400
  • Organization: Wolfram Research
  • Sender: owner-wri-mathgroup at wolfram.com

Michael Schaferkotter wrote:
> 
...
> 
> is there something about 0 here that i am not understanding?
> 
> this came up using Chop and Fourier.
> 

Mathematica distinguishes between an exact zero (0) and an inexact zero
(0. or 0.0).  N[0] is defined to be the exact 0.  In Mathematica version
2.2, Fourier only took a numerical argument.  In version 3.0, which will
be out soon, all of the commands above will return the Fourier transform
you would expect done useing machine precision complex numbers.

> Sqrt[2] > 2 returns
> 
> Sqrt[2] > 2

> Sqrt[0] > 0 returns
> 
> False.

This is because Sqrt[0] evaluates to 0, and 0 > 0 is False, but Sqrt[2]
is not  a number so the comparison is not made.

In Mathematica version 3.0, Sqrt[2] > 2 returns False.


Rob Knapp
WRI

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