On Fri, Nov 05, 2004 at 12:20:01AM +0000, ross@soi.city.ac.uk wrote:
On Thu, Nov 04, 2004 at 08:32:52PM +0100, Sven Panne wrote:
It's an old thread, but nothing has really happened yet, so I'd like to restate and expand the question: What should the behaviour of toRational, fromRational, and decodeFloat for NaN and +/-Infinity be? Even if the report is unclear here, it would be nice if GHC, Hugs, and NHC98 agreed on something. Can we agree on the special Rational values below?
[The proposal is to add 0:%0, 1:%0 and -1:%0 to Rational.]
I see that GHC has had this for a while, to handle reading floats: http://www.haskell.org//pipermail/cvs-libraries/2002-June/000231.html NHC solves that one by redefining read to bypass Rational on "NaN" and "Infinity". The NHC solution seems reasonable for read, but I still think a new type would be better for realToFrac. Hugs in CVS throws ArithException Overflow if any of the extra values are fed to toRational or decodeFloat. (Released Hugs has a bizarre bug there.)