Re: closed form of modulus function
From: Mitch Harris (harrisq_at_tcs.inf.tu-dresden.de)
Date: 02/11/05
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Date: Fri, 11 Feb 2005 09:58:09 +0100
Alex Hunsley wrote:
> The modulus function, which gives the 'magnitude' of a number (in effect
> removes a negative sign if one exists), can be expressed in closed form
> as either sqrt(x^2) or (sqrt(x))^2. Is either of these forms preferable?
> In practical terms, I think the former is the best, as it doesn't
> involve the possibility of imaginary numbers coming up during the
> calculation, which could cause an algorithm/computer program to object....
"closed form" is a slippery concept. It really just means "in a form
of my choosing" (for whoever utters it). Depending on your purposes,
you may just want to stick with "|x|" and manipulate that directly
rather than deal with the branches of the inverse of x^2.
-- Mitch Harris (remove q to reply)
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