On Sat, May 18, 2013 at 9:11 AM, TP
So the following version does not work: ---------------------------------------- [..] data Person :: Gender -> * where Dead :: Person Gender -- WHAT DO I PUT HERE Alive :: { name :: String , weight :: Float , father :: Person Gender } -> Person Gender
Here's the problem. In the line: Dead :: Person Gender you are referring to the Gender *type*, not the Gender kind. To refer to the kind instead, change this to: Dead :: forall (a :: Gender). Person a This means "for all types A which have the kind Gender, I can give you a Person with that type." The Alive declaration and deriving clause can be fixed in a similar way. Also, to enable the "forall" syntax, you need to add {-# LANGUAGE ExplicitForAll #-} at the top of the file. Chris -- Chris Wong, fixpoint conjurer e: lambda.fairy@gmail.com w: http://lfairy.github.io/