[Haskell-cafe] Re: Serialising types with existential data constructors

Misha Aizatulin wrote:

This is indeed the only solution I see so far. It has a serious problem though: as soon as I write the mapping, I limit once and for all the set of all types that can be used with my box. And I do so in a non-extensible way - if someone later would like to use my box with some other type in it, they wouldn't be able to.

This doesn't really help you now, but extending Haskell with open types and functions would solve this... http://www.informatik.uni-bonn.de/~loeh/OpenDatatypes.pdf http://haskell.org/haskellwiki/Extensible_datatypes -- Ashley Yakeley