Re: [Haskell-cafe] an instance in other than the last type parameters

Petr,

Short answer: you can't. Easiest way to workaround is to define a newtype wrapper around your original datatype:

newtype X' b a = X' {unX' :: X a b}

instance Functor (X' b) where fmap g (X' (X a b)) = X' (X b (g a))

Err.... fmap g (X' (X a b)) = X' (X (g a) b) Cheers, Stefan