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From: tgg@hplb.hpl.hp.com ()
Subject: Re: Substraction Problems :-(
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Date: Tue, 7 Mar 1995 13:46:31 GMT
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Allen Ethridge (ethridge@netcom.com) wrote:

|Which is what i really meant to get at.  It's not that i think the size
|of floats should be unrestricted so much as having the rules of numerical
|analysis applied by the computer (hardware or software).  If i remember my
|numerical analysis (from years ago) correctly, in the calculation of
|100.9 - 100.0 there can be no more than one significant digit to the right
|of the decimal point.  Why then would a computer produce a result that
|implied five significant digits - 0.90002.  It seems that this would force
|anyone writing programs with floating point numbers to right extra code
|to check all the intermediate results for the correct number of significant
|digits.  Why can't this be done automatically by the language/system/hardware?

This was a hot philosophical topic a couple of hundred years ago.

How many decimal digits are there to the right of 1/9 ?

How many digits are there to the  right of 4*arctan(1), where arctan() returns
the result in radians?

And  how  many  digits should  your "language/system/hardware" "automatically"
include?

--
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