On 22/07/14 14:02, adam vogt wrote:
Hi Leza,
I believe those instances are accepted in ghc-7.6. In future ghcs, it looks like there will be an extension that allows them again: https://phabricator.haskell.org/D69
In the meantime you could add another parameter for the 'e':
class Complexable csx rsx cel rel e | cel → csx, rel → rsx, e rsx → csx, csx -> e instance (RealFloat e) ⇒ Complexable [C e] [e] (C e) e e instance (RealFloat e) ⇒ Complexable [C e] [C e] (C e) (C e) e
Or you could keep the Complexable class as you had it, but write the instances for particular 'e' like:
instance Complexable [C Double] [Double] (C Double) Double
Regards, Adam
Ok Adam, I read more about this situation with type families and functional dependencies, and hope it will come soon to ghc. Meantime I will stay with type families and not to have these two instances simultaneously. Thanks. -- Leza Morais Lutonda, Lemol-C http://lemol.github.io 50 Aniversario de la Cujae. Inaugurada por Fidel el 2 de diciembre de 1964 http://cujae.edu.cu