[Haskell-beginners] Problems with lifting code

[PATRICK BROWNE]

Hi,
I am trying, without sucess, to run the code below from [1] (Section 4.3).
Obviouly I am missing something.
I would like to keep as close to the original code as possible.
Any help would be apreciated.
Regards,
Pat
[1] http://publik.tuwien.ac.at/files/pub-geo_2321.pdf

data MyNumbers a = MyNum a deriving Show

class (Floating a) => Numbers a where
 sqr :: a -> a

-- Not sure if i need these
-- instance Num (MyNumbers a) where
-- instance Fractional (MyNumbers a) where

class Lifts b a where
 lift0 :: a -> b a
 lift1 :: (a -> a) -> b a -> b a

instance Lifts MyNumbers a where
 lift0 x = MyNum x
 lift1 o x = MyNum (o x) -- **  Couldn't match expected type `a' with
actual type `MyNumbers a' **

instance (Floating (MyNumbers Float)) => Numbers (MyNumbers Float) where
  sqr x = lift1 sqr x  -- **  could not deduce (Numbers Float) arising from
a use of `sqr' **

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