Arrow Classes

[Dylan Thurston]

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On Tue, Jul 15, 2003 at 01:07:12AM -0700, Ashley Yakeley wrote:
> In article <200307141536.39157.qrczak@knm.org.pl>,
>  Marcin 'Qrczak' Kowalczyk <qrczak@knm.org.pl> wrote:
>=20
> > It doesn't provide instances of Num for anything which is already an in=
stance=20
> > of the other classes. And in Haskell 98 they must be defined separately=
 for=20
> > each type, instance (...) =3D> Num a doesn't work.
>=20
> It works in extended Haskell however, so I suspect it lays to rest the=20
> question of needing some other language extension.

I disagree!  This method (putting each function in its own class) does
not address two related points:

a) Being able to declare default values for a method declared in a
superclass;

b) Being able to refine a type heirarchy without the users noticing
(and without explosion of the number of instance declarations
required).

Peace,
	Dylan

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