[Haskell-cafe] Associated types
dave at zednenem.com
Thu Jul 1 14:48:01 EDT 2010
On Thu, Jul 1, 2010 at 2:35 PM, Christopher Lane Hinson
<lane at downstairspeople.org> wrote:
> On Thu, 1 Jul 2010, Christopher Lane Hinson wrote:
>>> Something like this should work:
>>> class (Path p, CompletePath (CompletedPath p)) => IncompletePath p where
>>> type CompletedPath p :: *
>> AIUI, this isn't implemented yet. You'll have to place the constraint on
>> involved function.
> I would have sworn I tested this in 6.12.x, but I'm wrong. It works.
> Isn't there something left unimplemented that I am thinking of? Tell me
> I'm not crazy!
Maybe you're thinking of equality superclasses. In another thread,
this example came up:
| class (DerivedOf a ~ derived) => Typecheck a derived where
which doesn't work yet, but should work in 6.14.
Dave Menendez <dave at zednenem.com>
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