Yes, I am running ghci 8.0.1.

Below, I have added the language pragmas suggested by the compiler

Regards,

Pat

.

{-#  LANGUAGE  MultiParamTypeClasses,FlexibleInstances,FlexibleContexts,UndecidableInstances #-}

data MyNumbers a = MyNum a deriving Show

class (Floating a) => 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 x = MyNum (o x) 

 

instance (Floating (MyNumbers Float)) => Numbers (MyNumbers Float) where

  sqr x = lift1 sqr x  

On 2 October 2016 at 16:38, Francesco Ariis <fa-ml@ariis.it> wrote:

On Sun, Oct 02, 2016 at 03:54:07PM +0100, PATRICK BROWNE wrote:
> 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
>

I get different errors from yours (missing extension, Illegal
instance declaration). Can you paste the exact file you are
loading with ghci (because you are using ghci, right?)?
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