Is there already a list class?

[David Roundy]

On Tue, Jan 09, 2007 at 05:54:11PM -0800, David Roundy wrote:
> I think you'd want a higher-kinded list type rather than a MPTC:
> 
> class List l where
>      cons :: e -> l e -> l e -- you can't make a constructor a member of a class
>      head :: l e -> e
>      null :: l e -> Bool
>      empty :: l e
>      ...

Okay, this was stupid of me.  As Spencer points out, we wouldn't actually
want a list type with kind * -> *, because we'd want to support specialized
lists like Data.Bytestring.  So we'd want something more like

> class List l e, l -> e where
>      cons :: e -> l -> l
>      head :: l -> e
>      null :: l -> Bool
>      empty :: l
>      ...

(But I don't like functional dependencies, because they confuse me, and
hope that associated types end up making it into Haskell'...)
-- 
David Roundy
http://www.darcs.net