Generalize indexing function

[Tom Ellis]

On Sun, Apr 11, 2021 at 12:03:04PM +0200, Henning Thielemann wrote:
> On Sun, 11 Apr 2021, Akhra Gannon wrote:
> 
> > It's distributive under IsList.
> > fromList (xs !! n) == (fromList xs) !! n
> 
> fromList (xs !! n) ?
> 
> I think, xs!!n is a single element.

Presumably `xs !! n == fromList xs !! n`