It is hard to tell from your code what you intend, but it works however you want it to, so long as it type checks. class Frame a where type Whatever a len :: Whatever a -> IO (Maybe Int) row :: Whatever a -> MaybeT IO (DifTomoFrame a DIM1) instance Frame DataFrameH5Path where type Whatever DataFrameH5Path = DataFrameH5 len = undefined -- :: DataFrameH5 -> IO (Maybe Int) row = undefined -- :: DataFrameH5 -> Int -> MaybeT (DifTomoFrame DataFrameH5Path DIM1) On Wed, Feb 22, 2017 at 11:19 AM, PICCA Frederic-Emmanuel <frederic-emmanuel.picca@synchrotron-soleil.fr> wrote:
Hello thanks, I will investigate, but I like this solution. I can ad more type to a type family right ?
Is it possible with this type family to be able to link in the other way ?
a -> t
Cheers
Fred _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners