MathGroup Archive 1990

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Re: N


The notions of precision and accuracy as used in Mathematica
are, in my view, wrong.  I have argued at some length (and
apparently with no effect) for a model in which a floating-point
number's precision can be extended by adding 0's to its
internal representation, if you wish.  The mathematica model
is (somewhat crudely) that if you write 0.5  you do not mean
0.500000...  but any number between 0.450 and 0.5499.. . 

While this latter model may be reminiscent of a physics-lab
approach of carrying significant figures in your measurements,
it is not useful in computation. Numerical analysis texts
talk about relative and absolute error, not precision and accuracy.

  Richard Fateman
  UC Berkeley



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