Hello Anatoly, On Sat, Apr 11, 2009 at 20:44, Anatoly Yakovenko wrote:

i am trying to understand how data.data works. How would i traverse the subterms of one type and build another type out of them. something like this:

...

gmapQ (\a -> Right a) (Just "hello")

I am not sure I understand what you're trying to do here. However, in general, 'gmapQ' is used in combination with 'mkQ' or 'extQ'. Those are not in Data.Data: you can import Data.Generics to get everything syb-related. Cheers, Pedro

<interactive>:1:0: Inferred type is less polymorphic than expected Quantified type variable `d' escapes In the first argument of `gmapQ', namely `(\ a -> Right a)' In the expression: gmapQ (\ a -> Right a) (Just "hello") In the definition of `it': it = gmapQ (\ a -> Right a) (Just "hello")

Thanks, Anatoly _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe