'Convertible' class?

[Hannah Schroeter]

Hello!

On Wed, Feb 07, 2001 at 03:43:59PM -0500, Dylan Thurston wrote:
> In thinking about various issues with the numeric classes, I came up
> with the following question:  Is there a problem with having a class
> 'Convertible' as follows?

> class Convertible a b where
>     convert :: a -> b

> [...]

Why not better:

class Subtype a b where {- a is subtype of b, if following operations exist -}
	inject :: a -> b
	project :: b -> Maybe a

Kind regards,

Hannah.