[Haskell-beginners] Problems with lifting code

[Imants Cekusins]

this works:


{-# LANGUAGE MultiParamTypeClasses,FlexibleInstances #-}
module Lift where

newtype MyNumbers a = MyNum a deriving Show

class Numbers a where
 sqr :: a -> a

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 (MyNum x) = MyNum (o x)

instance Numbers Float where
  sqr x = x * x

instance Numbers (MyNumbers Float) where
  sqr x = lift1 sqr x

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