Existential types: want better syntactic support (autoboxing?)

[Duncan Coutts]

On Mon, 2006-01-30 at 18:20 -0800, John Meacham wrote:
> so if I understand this proposal properly, it would mean the following
> 
> every single parameter type class whole parameter is of kind * 
> class Foo a where
> 
> automatically declares a data type defined as

perhaps semi-automatically?

class Foo a where
  ...
  ...
  deriving data Foo

> data Foo = exists a . Foo a => Foo_ a   
> (where Foo_ is some internal, non user accessable name)
> 
> and an instance
> 
> instance Foo Foo where
>         method (Foo_ x) = method x 
>         ...
> 
> this all seems quite nice, I really like it, we can always determine
> whether a name is a class or type from context (I think the only reason
> the namespaces are combined is due to import/export lists)


Duncan