On May 18, 11:57 am, Oscar Finnsson <oscar.finns...@gmail.com> wrote: > > forall d. gunfold k z c = k (z (DataBox::d->DataBox d)) > > Didn't work either. :(
I looked again at the paper (page 27): Haskell's Overlooked object system. http://homepages.cwi.nl/~ralf/OOHaskell/paper.pdf I think the forall is suppose to be in the constructor (as opposed to where I put it) and I don't think you need algebraic datatypes. data DataBox = forall d. (Show d, Eq d, Data d) => DataBox d I am not sure if this requires any extensions. Try it with and without the extension "explcit forall" You can also try this with a class called MakeDataBox and make d an instance of make data box. good luck. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
