That's approximately what I was describing, yes. Thanks!
On Fri, May 3, 2013 at 7:54 AM, Guy <guytsalmave...@yahoo.com> wrote: > David Thomas wrote: > >> I'd also like to see these two. It occurs to me there may be language >> tweak that could reduce breakage and add some >> convenience in both cases. It would not surprise me at all if this has >> been thought of, examined, and discarded, but I >> don't have time to dig so I'll just lay it out quickly, and if it has >> been discussed before someone will probably know >> where. >> >> The idea is to allow definitions of superclass operations in subclass >> instances. If there are such definitions, it's >> treated as if there were instances defined for each class (potentially a >> source translation, even). I think default >> definitions of superclass operations in the subclass would be used last >> (that is, only for the automatic instance of the >> superclass, and only if the superclass didn't have a default for that). >> >> This should allow existing instances of Num to just work (and I think >> Monad too, with some care). It would also mean if >> you're making something that's a Monad or a Num you could just lay out >> the one instance in all one place, reducing a bit >> of boilerplate. At the same time, you'd have the flexibility to just use >> the superclasses where you just want pieces. >> > > http://hackage.haskell.org/**trac/ghc/wiki/**DefaultSuperclassInstances<http://hackage.haskell.org/trac/ghc/wiki/DefaultSuperclassInstances> > > I'm surprised that the various superclass proposals haven't got more > attention, seeing as it would allow for this kind of class hierarchy > clean-up without breaking lots of code. > > > > ______________________________**_________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/**mailman/listinfo/haskell-cafe<http://www.haskell.org/mailman/listinfo/haskell-cafe> >
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