higher rank polymorphism

[Tomasz Zielonka]

On Wed, Nov 15, 2006 at 01:20:43PM +0100, Jan Christiansen wrote:
> I want to use a rank 2 data type and end up in typ problems that I  
> don't understand. I would really appreciate any hints to the  
> presented cases or pointers to interesting papers that address the  
> background of these problems.
> 
> I define the following datatype and a simple function that checks  
> whether the list is empty.
> 
> data Test = Test (forall a . [a -> a])

I would work, if you used existential quantification, but I am don't
know if it would be what you want:

data Test = forall a . Test [a -> a]

I don't know why you current code doesn't work - sorry.

Best regards
Tomasz