Re: N

*To*: mathgroup at yoda.ncsa.uiuc.edu*Subject*: Re: N*From*: uunet!renoir.Berkeley.EDU!fateman (Richard Fateman)*Date*: Thu, 22 Mar 90 11:56:21 -0800

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