From: "John W. Kennedy" <jwkenne@...>
Date: 2004-05-13T12:03:53+09:00
Subject: Re: Major Addition Bug?

Sean O'Dell wrote:
> Sort of makes me wonder if someone somewhere doesn't make a replacement FPU 
> that does all of its calculations as real decimal values, or at least 
> automatically corrects rounding errors.

First, because it takes more memory (or gives less precision), and is 
slower.  Second, because they're not "errors"; floating point arithmetic 
is intended for use in scientific computing, and reality does not come 
in neatly calibrated decimal fractions of meters, kilograms, and 
seconds; and artificially constraining calculations to decimal 
quantization actually increases error.

Now, /money/ is decimally quantized.  That's why IBM mainframes include 
decimal arithmetic, and why languages intended to be capable of 
accounting tasks (COBOL, PL/I, Ada '95, RPG, and some others) do decimal 
arithmetic, either by decimal hardware or by decimally scaled integer 
arithmetic (counting in pennies).  Java and Ruby have classes named 
BigDecimal for the same reason, though I am uncertain of whether Ruby's 
BigDecimal actually does what it seems to be advertising.

-- 
John W. Kennedy
"Only an idiot fights a war on two fronts.  Only the heir to the throne 
of the kingdom of idiots would fight a war on twelve fronts"
  -- J. Michael Straczynski.  "Babylon 5", "Ceremonies of Light and Dark"