[Haskell-cafe] Data.Generics: how do I get the type name of a value?

dataTypeOf ""

I've been learning/playing with Data.Generics a bit, and have a how-to question... If I say then I get

DataType {tycon = "Prelude.[]", datarep = AlgRep [[],(:)]}

No surprises there. But I'd really like to know that I have a String, or [Char]. How do I get the name of the concrete type that the list contains? Is that a reasonable thing to ask for? I can say:

gmapQ dataTypeOf "a" to get: [ DataType {tycon = "Prelude.Char", datarep = StringRep} , DataType {tycon = "Prelude.[]", datarep = AlgRep [[],(:)]} ]

But if I say:

gmapQ dataTypeOf "" I get: []

which makes sense when you consider the stucture of the List ADT, but doesn't help me determine the type of the value. Alistair