Re: Rounding??

["Andreas J. Guelzow" <aguelzow math concordia ab ca>]

Morten Welinder wrote:

>    Certainly but when you provide a mapping from one space (binary) to the
>    display space (decimal) is important that the display understands its
>    (numeric) context.  
>
> Users expect it, but it is not possible.
>
> An accountant will want "0.365" rounded to "0.36".  A mathematician
> will want "0.37".  Someone is not going to like the result.  The
> mathematician also wants "=sin(pi/4)-cos(pi/4)" to yield zero.  Don't
> count on it.

The mathematician also knows that computers don't use real numbers and 
is therefore not expecting this to be zero!

> Right now we are consistent in the best-approximation sense[*], I
> hope.  And no-one is happy, because -- as you say -- people generally
> do not think in binary.
>
> See the 0.62 release notes in your NEWS file for more information.
>
> Morten
>
>
>
> [*] The value of every subexpression is "rounded" to nearest valid
>     binary representable value.
But this is distinctfrom the expected formatting behaviour!

Andreas

--
Prof. Dr. Andreas J. Guelzow                    
Chair of Science
Concordia University College of Alberta
http://www.math.concordia.ab.ca/aguelzow