Re: Kindness of strangers (or strangeness of Kinds)

On Thu, Jun 7, 2012 at 2:46 AM, AntC 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#Kindsu...

José Pedro Magalhães writes: 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