Re: Floating-Point Numbers and Internal Representation

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sun, 4 Dec 2005 16:15:31 +0100, Matthias Kretschmer wrote:

> as I hope I said in my original posting, I am very well aware of this,
> but I had this special case where I wanted to use explicitly equality.
> There are times, when one is sure, that even with rounding errors, the
> two compared floating point numbers are really equal or not if one is
> using some good enough precision. So from some defined point on all
> following digits can be considered garbage, as it was in my case.

This is exactly definition of an interval: [xx.xxx0(0), xx.xxxx9(9)]

> The
> best solution would be that I had used Q (or a fixed subset of it)
> instead an approximation of R for my calculations, but I was too lazy :)

No, this contradicts to your statement about "following digits" being
garbage. In the case of Q they are not.

> Maybe I should take the time and port it to such a solution or implement
> something like that myself. At least in many circumstances using exact
> numbers instead of unexact ones causes much less trouble :)

Ah but this is a completely different story. If you *really* know that
multiplication and division are exact then Ada's fixed point types is just
what you need. Fixed point numbers are perfectly comparable.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de