It's first time I use TH. It would be nice to point out the motivations for using it.
If everything TH does is doable without it, the point of using it is write less code, eliminating some necessary and automatically computable code.
But I guess there is some more .....

paolino

2010/11/2 Antoine Latter <aslatter@gmail.com>
2010/11/1 Paolino <paolo.veronelli@gmail.com>:
> I think I've got something nice in the end.
>
> http://hpaste.org/41042/classsynonymhs
>
> example:
>
> class  (    ParteDi (Servizio a) s
>         ,    Read a
>         ,    Eq a
>         ,     Show a
>         ,     Integer `ParteDi` s
>         ) ⇒ SClass s a
>
> $(classSynonym ''SClass)
>
> ghci ":i SClass" command is printing some strange type variables but it
> compiles
>

Template Haskell might be overkill for this. In the past, I've done:

> class (Eq b, Show b, MyClass b, MyOtherClass b) => MySynonym b
> instance (Eq b, Show b, MyClass b, MyOtherClass b) => MySynonym b

I think this requires a couple of GHC extensions, but TemplateHaskell
is an extension as well. Maybe there are pitfalls with this approach.

Antoine