[Haskell-cafe] "SameConstraints?" type constraints

Hi All, I have the following data type: data S e where SC :: d -> e -> S e And I want to declare a Show instance for it in the following way: instance Show e => Show (S e) where show (SC x y) = show x ++ show y But, of course it don't typechecks because: could not deduce `Show d` arising from a use of `show`. Is there a way to constraint the `d` type in the `SC` constructor definition to have the same constraints of the `e` type? Something like: SC :: SameConstraints d e => d -> e -> S e ??? 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