Re: Floating-Point Numbers and Internal Representation

[Matthias Kretschmer <mccratch@gmx.net>]

On 2005-12-04, Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> wrote:
> On Sun, 4 Dec 2005 14:11:49 +0000 (UTC), Martin Dowie wrote:
>
>> Martin Krischik wrote:
>>> Independent of CPU/Language used I would allways suggest to use
>>> 
>>> abs (X - Y) < epsilon
>>> 
>>> with a sufficient but not to small epsilon instead.
>> 
>> Suggested reading:
>> 
>> http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm
>>
>> There is more than one answer to this problem...

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. 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 :)
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 :)

-- 
Matthias Kretschmer