Agreed. I wound up having to add a horrible Num instance for Bool in 'monoids' in order to support a decent Boolean Ring type.
http://comonad.com/haskell/monoids/dist/doc/html/monoids/Data-Ring-Boolean.html I would much rather be able to get rid of it! The only problem with eliminating the constraint is that any code that uses Bits polymorphically might have to pick up a Num annotation, but I can't see it being a serious problem. -Edward Kmett On Wed, Jun 24, 2009 at 8:13 AM, John Meacham <j...@repetae.net> wrote: > On Fri, May 08, 2009 at 04:36:41PM +0200, Stephan Friedrichs wrote: > > When looking for an xor function, I found one in Data.Bits but couldn't > > use it for Bool, because Bool is no instance of Bits and of Num (which > > would be necessary, because it's "class (Num b) => Bits b"). My question > > is: Why not? > > This has bothered me too. However, I think the root problem is that > 'Num' is a superclass of 'Bits'. There is no reason it should be, all > the default instances can be specified without the Num dependency. > > John > > -- > John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/ > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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