On Fri, 2009-11-27 at 11:07 +0100, Sebastian Fischer wrote:
We cannot write
class Name a where ... instance Name Name where ...
Yes! Very annoying. I want to be able to make a type that is the most general instance of a single-parameter type class. This is a useful OOish thing to do. For example: class Compiler c where getInstalledPackages :: c -> ... compileModule :: c -> ... instance Compiler GHC where ... instance Compiler NHC where ... and sometimes I want a list of compilers... newtype Compiler where Compiler :: Compiler c => c -> Compiler deriving Compiler compilers :: [Compiler] compilers = [Compiler ghc, Compiler nhc]
Does anyone know why types and values are in separate namespaces but classes and types are not?
I think it's because you cannot currently distinguish them in module import/exports. Duncan