it's an .lhs file
 
> data Alumno = A { dni :: Integer, nombre :: String,nota::Float }
> shf :: Alumno -> String
> shf alum  = show (dni alum) ++ nombre alum  ++ show (nota alum )
 
i don't wanna use this sentence:  deriving Show
i wanna use "my show function" but ...
Here is the problem !!
 
> instance Show a => Show (Alumno  a) where
>      show x = shf x
 
 
Thanks .