Re: [Haskell-beginners] Haskell wants the type, but I only know the class.

Thank you, David and Antoine. I was planning to have files containing different types of objects, but where all of the types are instances of a particular class. Since the class definition ensures that whatever the types are, they implement the methods that I need, I hoped to be able to manipulate the files using those methods, without having to find out the class programmatically. Clearly I need to rethink this. I'm looking into existentially quantified data constructors now, maybe that will help.