On Sat, Jul 05, 2003 at 08:24:32PM +0100, Jon Fairbairn wrote:
On 2003-07-05 at 19:43+0200 Steffen Mazanek wrote:
a quit funny hugs session:
Prelude> 0.5::Rational 1 % 2 Prelude> 0.1::Rational 13421773 % 134217728 Prelude> 13421773/134217728 0.1
I do not know how this fraction is calculated, but it does not fit my expectations :-)
Remember that internally arithmetic is binary, and that 0.1 can't be expressed exactly as a floating point number. I think that's the explanation.
Ok, ok, it is no bug...
No, I think it is a bug: 0.1 ought to be equivalent to fromRational (1%10), but Hugs isn't intended for numerical work. GHCi gets the right answer.
Yes, Hugs represents floating point literals in binary, and it's not intended for the numeric work. But the CVS version already contains a hack that usually converts these literals back to the right Rational: Prelude> 0.1::Rational 1 % 10 Prelude> 0.0123456789::Rational 123456789 % 10000000000 Prelude> 2.2e-9::Rational 11 % 5000000000 The real fix would be to keep the literals as Rationals, but this would be too expensive in the Hugs setting.