[Haskell-cafe] understanding generics
aeyakovenko at gmail.com
Sat Apr 11 14:44:10 EDT 2009
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")
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")
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