[Haskell-beginners] about kind of (->)

[Ertugrul Söylemez]

Song Zhang <vxanica at gmail.com> wrote:

> a function has also a kind. According to haskell report 2010 4.1.2 it
> is * -> * -> *, which is easy to understand. However in ghci I type :k
> (->). the output is ?? -> ? -> *. I want to know what do ??  and ?
> mean. Thanks

This has to do with primitive types like Int#.  It basically says that
the input type can be a primitive type, and if it is, then the output
type must also be primitive.

In fact since GHC 7.4 (or perhaps earlier) the kind is

    * -> * -> *

as expected.


Greets,
Ertugrul
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 836 bytes
Desc: not available
URL: <http://www.haskell.org/pipermail/beginners/attachments/20120616/8f2973a5/attachment.pgp>