What promotes to (* :: BOX) ?

[Iavor Diatchki]

Hello,

I've been using an existential quantifier for this.  It
looks weird (and I think we should fix this as discussed) but it is the
current workaround:

data MyKind = forall star. T star

-- T :: * -> MyKind

-Iavor




On Tue, Apr 2, 2013 at 7:11 AM, Richard Eisenberg <eir at cis.upenn.edu> wrote:

> For more immediate satisfaction (i.e., before we get around to updating
> GHC in the manner suggested on the wiki page), you have to use a
> parameterized type and then specialize it to *:
>
> > data Prom2 a = Typic a
>
> Now, we have (Prom2 * :: BOX) with (Typic Int :: Prom2 *).
>
> Unfortunately, we have no kind synonyms, so you have to insert the *
> parameter every time you want to use the Prom2 kind. As Pedro suggests,
> this is a known weakness of the current system.
>
> Richard
>
> On Apr 2, 2013, at 8:55 AM, José Pedro Magalhães <jpm at cs.uu.nl> wrote:
>
> Hi Gabor,
>
> See http://hackage.haskell.org/trac/ghc/wiki/GhcKinds/KindsWithoutData
> Comments on that discussion are welcome.
>
>
> Cheers,
> Pedro
>
> On Tue, Apr 2, 2013 at 2:51 PM, Gabor Greif <ggreif at gmail.com> wrote:
>
>> Hi devs!
>>
>> I guess I found a gap in the promotion mechanism:
>>
>> > data Prom1 = Symic Symbol
>>
>> gets promoted to to a kind (Prom1 :: BOX) with (Symic "AAA" :: Prom1).
>> So far so good.
>>
>> But how can I define by promotion (Prom2 :: BOX) with (Typic Int ::
>> Prom2) ?
>>
>> I'd like to write
>>
>> > data Prom2 = Typic Type
>>
>> but haven't found such a beast in TypeLits. So my question is
>> basically, which type-level identifier promotes to (* :: BOX) when
>> mentioned in a `data` definition?
>>
>> I am thankful for any hints!
>>
>> Cheers,
>>
>>     Gabor
>>
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>
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