Re: Querying the instances a data type implements

On Sun, Jan 17, 2010 at 6:42 PM,  <[email protected]> wrote:
> Hi,
>
> I am trying query the instances that a data type implements. Calling reify
> on the data type doesn't appear to return anything relating to type classes.
>
> I am very new to Template Haskell, so I apologize if there is a easy way to
> do this that I missed.
>
> -Jonathan

I do not believe that this is possible (getting instances based on
type).  It, I suppose, would be possible theoretically to get at least
instances in-scope, but, as type classes are open, this wouldn't,
necessarily, be all type classes the date type implements.  But I
don't believe there's any support for navigating to instances from
types.

As an aside, you'd be better off sending queries about Template
Haskell to the [email protected] mailing list, as this (TH)
mailing list is very lightly used and there's been talk of getting rid
of it.  Probably anybody subscribed to this list is also subscribed to
Haskell Cafe as well.