1{-# LANGUAGE TypeOperators #-} 2 3import GHC.Generics 4 5class Yo f where 6 yo :: f x -> Int 7 8instance (Yo f, Yo g) => Yo (f :*: g) where 9 yo (fx :*: gx) 10 = let 11 fx_c = yo fx 12 gx_c = yo gx 13 in _w0 fx_c gx_c 14 15