What promotes to (* :: BOX) ?

[Gabor Greif]

On 4/2/13, Iavor Diatchki <iavor.diatchki at gmail.com> wrote:
> 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

Hi Iavor,

thanks for the tip, this works nicely. I only have to restrict (t :: T
*) everywhere a MyKind is needed, to get what I want.

I tried Richard's solution too (with a universally quantified extra
parameter). It appeared to work too, but it needed much more extra
annotations. I believe a kind synonym would have helped, but we do not
have those, right?

Cheers,

    Gabor

>
> -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
>>>
>>> _______________________________________________
>>> ghc-devs mailing list
>>> ghc-devs at haskell.org
>>> http://www.haskell.org/mailman/listinfo/ghc-devs
>>>
>>
>> _______________________________________________
>> ghc-devs mailing list
>> ghc-devs at haskell.org
>> http://www.haskell.org/mailman/listinfo/ghc-devs
>>
>>
>>
>> _______________________________________________
>> ghc-devs mailing list
>> ghc-devs at haskell.org
>> http://www.haskell.org/mailman/listinfo/ghc-devs
>>
>>
>