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lotz84/polymorphic-higher-order-type.hs

Created April 13, 2015 02:24
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polymorphic-higher-order-type.hs
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ExistentialQuantification #-}
data ShowBox = forall s. Show s => SB s
instance Show ShowBox where
show (SB s) = show s
heteroList :: [ShowBox]
heteroList = [SB (), SB 5, SB True]
main = print heteroList
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