Hello, On Mon, Feb 13, 2012 at 5:32 PM, Edward Kmett <ekm...@gmail.com> wrote: > > There are fewer combinators from commonly used classes for working with > the left argument of a bifunctor, however. >
I think that the bifunctor part of Bas's version is a bit of a red herring. What I like about it is that it overloads exactly what needs to be overloaded---the representation of the type---without the need for any fake parameters. To make things concrete, here is some code: > newtype TypeRepT t = TR TypeRep > > class Typeable t where > typeRep :: TypeRepT t > > instacne Typeable Int where typeRep = TR type_rep_for_int > instance Typeable [] where typeRep = TR type_rep_for_list The two formulations support exactly the same interface (you can define `Proxy` and the proxied `typeRep` in terms of this class) so I wouldn't say that the one is easier to use that the other, but I think that this formulation is slightly simpler because it avoids the dummy parameter to typeRep. -Iavor
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