[Haskell-beginners] Problems with lifting code

[PATRICK BROWNE]

So it seems that
 (1) lift1 o x = MyNum (o x)
Needed to be rewritten to
(2)  lift1 o (MyNum x) = MyNum (o x)
I am not sure  why the constructor is used on the LHS of (2)
Thanks for all your help.
Pat


On 2 October 2016 at 17:03, PATRICK BROWNE <patrick.browne at dit.ie> wrote:

> 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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>>
>
>

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