There is a little, ill-documented, sub-kind hierarchy in GHC. I'm trying hard to get rid of it as much as possible, and it is much less important than it used to be. It's always been there, and is nothing to do with polykinds.
I've extended the commentary a bit: see "Types" and "Kinds" here
http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler
The ArgKind thing has gone away following Max's recent unboxed-tuples patch, so we now only have OpenKind (described on the above pages).
Simon
| -----Original Message-----
| From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-
| users-bounces@haskell.org] On Behalf Of AntC
| Sent: 08 June 2012 00:37
| To: glasgow-haskell-users@haskell.org
| Subject: Re: Kindness of strangers (or strangeness of Kinds)
|
| José Pedro Magalhães writes:
|
| > On Thu, Jun 7, 2012 at 2:46 AM, AntC clear.net.nz>
| wrote:
| >
| > What does the `ArgKind' message mean?
| >
| > `ArgKind` and `OpenKind` is what previously was called `?` and `??`
| > (or the
| otherway around; I can't remember).
| http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/TypeType#Ki
| ndsubty
| ping
|
| Thanks Pedro, I'm trying to understand what's changing and why. (And I'd
| better repeat that I'm looking at 7.4.1, not HEAD; and SPJ's being
| perfectly clear that the promoted Kind stuff is not yet officially
| approved for prime
| time):
|
| GHC 7.2.1> :k (->) :: ?? -> ? -> *
|
| GHC 7.4.1> :k (->) :: * -> * -> *
|
| At first sight (->) is becoming less polyKinded. Is the eventual aim to
| be:
|
| GHC 7.6+> :k (->) :: AnyKind1 -> AnyKind2 -> *
|
|
|
| >You might also want to have a look at Richard and Stephanie's latest
| >paper
| draft, about singletons, which is related to what you are trying in your
| example:http://www.cis.upenn.edu/~eir/papers/2012/singletons/paper.pdf
| >
|
| That's what I'm doing, and trying to understand the machinery behind it.
| The
| naieve approach I started with was how to get one-way from type to its
| single
| value -- I wasn't aiming for the whole singleton gig.
|
| AntC
|
|
|
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