Hi Yotam,
One way to do this is to take an `Either Foo Bar` as an argument instead,
then you can pattern match on its Left and Right. This is preferable if the
function is only meant to work for a limited number of types. If you want
it to be extensible to any number of types you can write a typeclass that
contains `func` with the same type signature as you have now. There are
also some extensions built in to GHC to do this automatically for you, but
I don't recall exactly which ones to enable...
HTH,
Adam
On Tue, 10 Oct 2017 at 18:58 Yotam Ohad
Hello cafe, I am trying to do the following:
data Foo = Foo { a1 :: Int -> Int, a2 :: Int -> Char } data Bar = Bar { a1 :: Int -> Int }
func :: a -> Maybe (Int -> Int) -- a is either Foo or Bar func (x::(Bar/Foo) = Just $ a1 x func _ = Nothing
I'm not sure how to implement this. All I know that the types are matching so I think it could be possible.
Thanks for your help -Yotam _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.