Hello,
I recently ran into a problem using numbers that require Double precision
floating point. Hugs seems to always convert to single precision Float.
Here is an example:
> f :: Float
> d, d2 :: Double
> f = 3.141592654
> d = 3.141592654
> d2 = fromRational (3141592654 % 1000000000)
> main = do
> putStrLn (show (round (f * 1000000000)))
> putStrLn (show (round (d * 1000000000)))
> putStrLn (show (round (d2 * 1000000000)))
Surprisingly, this gives:
3141592832
3141592832
3141592832
Here is a similar C program:
> int main(void)
> {
> float f = 3.141592654;
> double d = 3.141592654;
>
> printf("%.9f\n", f);
> printf("%.9f\n", d);
> }
3.141592741
3.141592654
Also, I would expect that at least the single precision case is identical
in both examples, but it's not. Weird...
Besides, how can I influence how floating point numbers are converted to
strings (precision, format, etc.)?
Thanks,
Andreas.
------------------------------------------------------------------------
Andreas Gruenbacher gruenbacher(a)geoinfo.tuwien.ac.at
Research Assistant Phone +43(1)58801-12723
Institute for Geoinformation Fax +43(1)58801-12799
Technical University of Vienna Cell phone +43(664)4064789
