Dan Piponi wrote:
To use these types with ghc you need to use the compilation flag -XExistentialQuantification.
Or, more portably, add {-# LANGUAGE ExistentialQuantification #-} at the top of the source file. It should now compile in any computer that supports this feature without any special command-line flags.
There's more to be found here: http://www.haskell.org/haskellwiki/Existential_typ
Amusingly, half of this article is still the text that I wrote. ;-) _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
