On 4/24/07, Jacques Carette
In Ocaml, you can frequently use polymorphic variants to get the same effect.
Which means that if you are willing to do enough type-class-hackery, it should, in principle, be possible to do the same in Haskell. But it sure isn't as convenient!
You seem to imply that there is an encoding of polymorphic variants in Haskell using type classes. While I know that it's possible to achieve similar effects using type classes I haven't seen a direct encoding. If there is such an encoding I would be very interested to hear about it.
This all points to some clear need for more ``flavours'' of polymorphism being needed (in Haskell), to be able to express *in the type system* what TH allows you to say "outside".
I totally agree with this. Cheers, Josef