Re: Possreps and numeric types

"V.J. Kumar" <vjkmail_at_gmail.com> wrote in message news:Xns98FFEB79C9D6Bvdghher_at_217.22.228.20...
> Matthias Klaey <mpky_at_hotmail.com> wrote in
> news:gqsg031cmfnr5p5fbiokksmaf8psios4hh_at_4ax.com:
>
> > I used to teach that if you calculate "2 + 2" on a computer, the
> > result would be somewhere between 3 and 5,
>
> You are kidding, right ? If not, you might want to fix your computer for
> the sake of your poor students at least !

I think you missed the irony in the original teaching. If you are working with integers,
there is only one answer that is somewhere between 3 and 5. Everything works. If you are working with floating point numbers, and approximations, you can get some nasty surprises.

Some decades back, some of us had to find out why the books were out of balance by a penny. The answer turned out to be inappropriate use of binary floating point numbers to represent decimal fractions of currency amounts. Eventually, the round off errors produced a discrepancy visible to the guys with green eyeshades. (Younger folks may need a lesson in history for this one). I don't remember how much labor we put into that one, but it was more than a penny's worth. Received on Tue Mar 27 2007 - 08:15:06 CEST