On Wed, Feb 07, 2001 at 10:19:33PM +0100, Hannah Schroeter wrote:
> 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
Shouldn't this be a subclass? 'project' is not always easy or
possible to define.
Best,
Dylan
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