[Haskell-beginners] Problems with lifting code

[PATRICK BROWNE]

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 at 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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