On Apr 15, 2010, at 3:44 PM, Sittampalam, Ganesh wrote:
You were trying to choose between different top-level types (which happen to be instances of the same family) by their constructors.
That is true. I was trying to emulate an open data type such that I can write -- does not work fffuuuu :: DataFam a -> a -> Int fffuuuu BoolDataFam True = 42 fffuuuu CharDataFam 'c' = 43 But apparently such thing is only possible with a (closed) GADT: data GADT a where BoolGADT :: GADT Bool CharGADT :: GADT Char -- does work foo :: GADT a -> a -> Int foo BoolGADT True = 42 foo CharGADT 'c' = 43 I was hoping to achieve the same without having a single closed type. On Apr 15, 2010, at 3:29 PM, Dan Doel wrote:
DataFam Bool is not a GADT, it's an ADT written with GADT syntax.
Yes, that was the main source of my confusion. Thank you both for clarifying! Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)