Re: Double: 2 Decimal points


"tex" <NoSpam@xxxxxxxxxxx> wrote in message
news:VT5Ie.35$RS.3@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> One problem I have with this is that (1.0 / 3.0) + (1.0 / 3.0) + (1.0 /
>> 3.0) and ((1.0 + 1.0 + 1.0)/ 3.0) have a result that differs by 10%, and
>> that my experience is that the compiler doesn't always catch that, and
>> that mainframe programmers don't always think about that.
>
> This has nothing to do w/ integer vs floating pt arithmetic, but rather
> the
> problem is that computers, having finite representations of numbers,
> cannot
> do math correctly, PERIOD! (a x b)/c does not always equal a x (b/c)
> on a computer and this is true regardless of number representation or
> compiler.

This isn't strictly true; some computing environments do calculations in
a symbolic manner instead of numerical (e.g. matlab).

If you declare N = 1, D = 3, and X = N/D, it does not store 0.3333...
into X, but actually stores the equation N/D. If you later multiply X by 3,
it will be able to perform the simplification and store X = N, which gives
the correct result.

- Oliver


.

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