Re: [Haskell-beginners] How to link two Types

I should mention I just wrote that code off the cuff. It's probably not even close to right. I recommend you mess with type families a little to see if they get you where you want to go in your existing code. On Wed, Feb 22, 2017 at 11:29 AM, David McBride wrote:

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 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