I've put some of Oleg's code on hackage, named polytypeable. > import Data.PolyTypeable > main = print [polyTypeOf Nothing, polyTypeOf Just]
This prints [Maybe a1,a1 -> Maybe a1] To get a list of the actual constructors you need to derive Data.Data.Data and use that. -- Lennart On Wed, Dec 30, 2009 at 8:46 PM, Claude Heiland-Allen <claudiusmaxi...@goto10.org> wrote: > Gregory Propf wrote: >> >> Say I have something like >> >> data DT a = Foo a | Bar a | Boo a >> >> I want something like a list of the constructors of DT, perhaps as >> [TypeRep]. I'm using Data.Typeable but can't seem to find what I need in >> there. Everything there operates over constructors, not types. > > The approach below won't work in general because the constructors may have > different (argument) types, but for the above: > > [Foo, Bar, Boo] :: [a -> DT a] > > And you could manually build a list of constructor types, as a try: > > [typeOf Nothing, typeOf Just] :: [TypeRep] > > which doesn't work, due to polymorphic ambiguity, so you'd have to: > > [typeOf (Nothing :: Maybe Int), typeOf (Just :: Int -> Maybe Int)] > > In general, maybe Data.Dynamic is what you need, but I don't think that can > handle polymorphic values yet either. > > What do you want to do with the list of constructors once you have them? > > Where are they defined? > > > Claude > -- > http://claudiusmaximus.goto10.org > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe