Sebastian Fischer wrote:
With GADTs, the specific choice of constructor is what gives you the type matching functionality.
My intention was to use a GADT as data family instance (hence, I wrote it in GADT style and it was accepted as such). Can't GADTs be used as data family instances?
I'm not aware of any restriction there, but that's not the issue here. You were trying to choose between different top-level types (which happen to be instances of the same family) by their constructors. GADTs allow you to choose between different constructors of the *same* top-level type. If DataFam Bool had multiple constructors, you could choose between them in fffuuuu. But fffuuuu would have to have type DataFam Bool -> Bool -> Int (as is necessary with your originally posted code). Ganesh =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================