[Python-Dev] Round Bug in Python 1.6?

[Christian Tismer]

Ka-Ping Yee wrote:
> 
> On Sun, 9 Apr 2000, Christian Tismer wrote:
> > Here is the problem, as I see it:
> > You say if you type 3.1416, you want to get exactly this back.
> > But how should Python know that you typed it in?
> > Same in my case: I just rounded to 3 digits, but how
> > should Python know about this?
> >
> > And what do you expect when you type in 3.14160, do you want
> > the trailing zero preserved or not?
> 
> It's okay for the zero to go away, because it doesn't affect
> the value of the number.  (Carrying around a significant-digit
> count or error range with numbers is another issue entirely,
> and a very thorny one at that.)
> 
> I think "fewest digits needed to distinguish the correct value"
> will give good and least-surprising results here.  This method
> guarantees:

Hmm, I hope I understood.
Oh, wait a minute! What is the method? What is the correct value?

If I type
>>> 0.1
0.10000000000000001
>>> 0.10000000000000001
0.10000000000000001
>>> 

There is only one value: The one which is in the machine.
Would you think it is ok to get 0.1 back, when you
actually *typed* 0.10000000000000001 ?

-- 
Christian Tismer             :^)   <mailto:tismer@appliedbiometrics.com>
Applied Biometrics GmbH      :     Have a break! Take a ride on Python's
Kaunstr. 26                  :    *Starship* http://starship.python.net
14163 Berlin                 :     PGP key -> http://wwwkeys.pgp.net
PGP Fingerprint       E182 71C7 1A9D 66E9 9D15  D3CC D4D7 93E2 1FAE F6DF
     where do you want to jump today?   http://www.stackless.com