ref: b9f2c8f2ae01ab8a0a168fd7136e94c2eb8a7b48
dir: /tests/Exists.hs/
module Exists(main) where
import Prelude
data E = forall a . Show a => C a
es :: [E]
es = [C True, C 'a', wrap (C (1::Int))]
instance Show E where
show (C a) = show a
wrap :: E -> E
wrap (C a) = C [a]
eio :: IO E
eio = return (C True)
someE :: E
someE = C (Just 'a')
foo :: E -> String
foo x | C a <- x = show a
bar :: E -> String
bar x =
case x of
C a -> show a
data T a = Show a => T a
sh :: forall a . T a -> String
sh (T a) = show a
main :: IO ()
main = do
print es
C x <- eio
print x
putStrLn (foo someE)
putStrLn (bar someE)
putStrLn (sh (T True))
putStrLn (sh (T 'x'))