Henning Thielemann wrote:
On Mon, 27 Oct 2008, L.Guo wrote:
I think this is unresonable. then try it in GHC 6.8.3.
Prelude> round 3.5 4 Prelude> round 2.5 2
Is there any explanation about that ?
It's the definition we learnt in school ...
Hmm, Henning, this is strange. The two of us went to the very same school, but I know for a fact that I learnt 2.5 to round to 3, not 2 as above. ;-)
I think one reason is that repeated rounding should not be worse than rounding in one go. Consider the rule 'use ceiling when the first removed digit is 5'. Then
0.45 - (round to one place) -> 0.5 - (round to integer) -> 1
but
0.45 - (round to integer) -> 0
That is of course true (and was the topic of heated discussion with my fourth grade math teacher), but does not explain 2.5 -> 2. Ciao, Janis. -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de