[Haskell-cafe] Problems translating Conor McBride's talk into Haskell + DataKind + KindPoly
José Pedro Magalhães
jpm at cs.uu.nl
Fri Oct 26 08:27:11 CEST 2012
Please use GHC 7.6 for experimenting with PolyKinds/DataKinds; the
implementation in 7.4 was not fully complete. Your code compiles fine in
On Fri, Oct 26, 2012 at 3:10 AM, Ahn, Ki Yung <kyagrd at gmail.com> wrote:
> Promotion works for user defined lists such as
> data List a = Nil | Cons a (List a)
> And, if I use (List Bool) instead of [Bool] everything works out.
> It's only the Haskell list type constructor  is being a problem.
> In the "Giving Haskell a promotion" paper, it says that Haskell lists are
> "natively promoted". I believe this means that it is treated specially
> somehow. I don't know how it is implemented but what GHC 7.4.1 does
> specially for Haskell lists has some problems. So, it's clearly not a
> limitation of DataKind and PolyKind extension, but that special routine for
>  is the issue.
> I might have to write bug report.
> On 2012년 10월 25일 18:07, Ahn, Ki Yung wrote:
>> Most part of Conor's talk at ICFP, until just before the last stage
>> where he heavily uses true value dependency for compiler correctness all
>> the code seemed to be able to translate into Haskell with the new hot
>> DataKinds and PolyKinds extension.
>> I tried it in GHC 7.4.1 and it was possible to do it, but I got stuck
>> and I had to make the generic list structure mono-kinded with kind
>> signatures rather not use the PolyKinds extension.
>> I wonder if this is just a but of GHC 7.4.1's implementation of
>> PolyKinds, or a limitation of the DataKind design.
>> I attached a literate Haskell script with this message that illustrates
>> this problem.
>> Thanks in advance for any comments including whether it runs in later
>> versions or still has problems, and discussions about the DataKinds and
>> PolyKinds extension.
>> Ki Yung
>> Haskell-Cafe mailing list
>> Haskell-Cafe at haskell.org
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
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