Re: [Haskell-cafe] Rank N type tutorial?

27 Oct 2006

      On 27/10/06, David House  wrote:
...
heteroList' = [MkT' 5, MkT' (), MkT' True]
main = mapM_ print heteroList'
{- prints:
5
()
True
-}
Sorry, the definition of main is a bit off. It should read:

main = mapM_ (\(MkT' x) -> print x) heteroList'

Of course you have to unpack the MkT' first (or define a Show instance
for T', noting that you can't derive anything on existentials).

-- 
-David House, dmhouse@gmail.com