how to write a derivable class?

Question

i have this

data Something = Something Integer deriving (MyClass, Show)

class MyClass a where   
    hello :: MyClass a => a -> a

instance MyClass In         


        

Answer 1

You may want to have a look at the GHC documentation on Generic Programming.
You need to create a class that can work on a generic representation of arbitrary types. I don't think the specific example you gave is reasonable for a derivable class.