Haskell' - class aliases

[John Meacham]

On Thu, Apr 24, 2008 at 08:48:15PM +0200, Wolfgang Jeltsch wrote:
> Am Mittwoch, 23. April 2008 06:18 schrieb John Meacham:
> > On Tue, Apr 22, 2008 at 08:33:53AM +0100, Simon Peyton-Jones wrote:
> > > Is this the most up-to-date description of the proposal?
> > >         http://repetae.net/recent/out/classalias.html
> >
> > There were a few changes proposed in the discussion that followed my
> > announcement that I wanted to make. The one I can remember now is
> > getting rid of the 'alias' keyword since the equals sign unabiguously
> > identifies it as an alias. I will dig through the archive to find the
> > others..
> 
> I also have some remark: Why not write
> 
> > class Eq a => Num a = (Additive a, Multiplicative a)
> 
> instead of
> 
> > class Num a = Eq a => (Additive a, Multiplicative a)

Well, because you can think of 'Num a' as an alias for 'Eq a =>
(Additive a, Multiplicative a)', not that Eq is a superclass of Num
which the class declaration syntax implies.

        John

-- 
John Meacham - ⑆repetae.net⑆john⑈