Changes to Typeable

[John Meacham]

Proxy also has the advantage that it almost exactly mirrors what it
ends up looking
like in core. The application to proxy is the user visible type application.

    John

On Tue, Feb 14, 2012 at 8:18 AM, Iavor Diatchki
<iavor.diatchki at gmail.com> wrote:
> Hello,
>
> On Mon, Feb 13, 2012 at 5:32 PM, Edward Kmett <ekmett at gmail.com> wrote:
>>
>> There are fewer combinators from commonly used classes for working with
>> the left argument of a bifunctor, however.
>
>
> I think that the bifunctor part of Bas's version is a bit of a red herring.
>  What I like about it is that it overloads exactly what needs to be
> overloaded---the representation of the type---without the need for any fake
> parameters.  To make things concrete, here is some code:
>
>> newtype TypeRepT t = TR TypeRep
>>
>> class Typeable t where
>>   typeRep :: TypeRepT t
>>
>> instacne Typeable Int where typeRep = TR type_rep_for_int
>> instance Typeable []  where typeRep = TR type_rep_for_list
>
> The two formulations support exactly the same interface (you can define
> `Proxy` and the proxied `typeRep` in terms of this class) so I wouldn't say
> that the one is easier to use that the other, but I think that this
> formulation is slightly simpler because it avoids the dummy parameter to
> typeRep.
>
> -Iavor
>
>
>
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