John Lato
writes: What about Data.Typeable.typeRepArgs ? typeRepArgs :: TypeRep -> [TypeRep] Prelude Data.Data> typeRepArgs (typeOf Foo)[Int,Foo]
Thanks John, I did look at that, and thought it returned only type args, not the 'baked in' type. Your example applies to `(typeOf Foo)` -- that is, the data constr, which is indeed a function. And `typeOf Foo` is `Int -> Foo`, as I noted in the OP. I want something that can apply to a value of type Foo. (`someFoo`, in my example.)
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For anything more complicated, I suspect you'll need Data/Generic/Template Haskell.
That is rather what I feared. I want to avoid TH, because that imposes on my user. Could you point to where/what in Data/Generics?
newtype Foo = Foo Int deriving (Read, Show, Typeable, Data, ...) someFoo = Foo 7
I can ask for `typeOf someFoo` and get `Foo` OK. I can ask for `typeOf Foo` and get `Int -> Foo` OK. If I ask for `typeOf (typeOf someFoo)` I get `TypeRep`. `typeOf (show $ typeOf someFoo`) gets me `[Char]` (aka `String`)
What I want is to get the based-on type baked inside `someFoo`